Age Owner Branch data TLA Line data Source code
1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * dsa.c
4 : : * Dynamic shared memory areas.
5 : : *
6 : : * This module provides dynamic shared memory areas which are built on top of
7 : : * DSM segments. While dsm.c allows segments of memory of shared memory to be
8 : : * created and shared between backends, it isn't designed to deal with small
9 : : * objects. A DSA area is a shared memory heap usually backed by one or more
10 : : * DSM segments which can allocate memory using dsa_allocate() and dsa_free().
11 : : * Alternatively, it can be created in pre-existing shared memory, including a
12 : : * DSM segment, and then create extra DSM segments as required. Unlike the
13 : : * regular system heap, it deals in pseudo-pointers which must be converted to
14 : : * backend-local pointers before they are dereferenced. These pseudo-pointers
15 : : * can however be shared with other backends, and can be used to construct
16 : : * shared data structures.
17 : : *
18 : : * Each DSA area manages a set of DSM segments, adding new segments as
19 : : * required and detaching them when they are no longer needed. Each segment
20 : : * contains a number of 4KB pages, a free page manager for tracking
21 : : * consecutive runs of free pages, and a page map for tracking the source of
22 : : * objects allocated on each page. Allocation requests above 8KB are handled
23 : : * by choosing a segment and finding consecutive free pages in its free page
24 : : * manager. Allocation requests for smaller sizes are handled using pools of
25 : : * objects of a selection of sizes. Each pool consists of a number of 16 page
26 : : * (64KB) superblocks allocated in the same way as large objects. Allocation
27 : : * of large objects and new superblocks is serialized by a single LWLock, but
28 : : * allocation of small objects from pre-existing superblocks uses one LWLock
29 : : * per pool. Currently there is one pool, and therefore one lock, per size
30 : : * class. Per-core pools to increase concurrency and strategies for reducing
31 : : * the resulting fragmentation are areas for future research. Each superblock
32 : : * is managed with a 'span', which tracks the superblock's freelist. Free
33 : : * requests are handled by looking in the page map to find which span an
34 : : * address was allocated from, so that small objects can be returned to the
35 : : * appropriate free list, and large object pages can be returned directly to
36 : : * the free page map. When allocating, simple heuristics for selecting
37 : : * segments and superblocks try to encourage occupied memory to be
38 : : * concentrated, increasing the likelihood that whole superblocks can become
39 : : * empty and be returned to the free page manager, and whole segments can
40 : : * become empty and be returned to the operating system.
41 : : *
42 : : * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
43 : : * Portions Copyright (c) 1994, Regents of the University of California
44 : : *
45 : : * IDENTIFICATION
46 : : * src/backend/utils/mmgr/dsa.c
47 : : *
48 : : *-------------------------------------------------------------------------
49 : : */
50 : :
51 : : #include "postgres.h"
52 : :
53 : : #include "port/atomics.h"
54 : : #include "port/pg_bitutils.h"
55 : : #include "storage/dsm.h"
56 : : #include "storage/lwlock.h"
57 : : #include "utils/dsa.h"
58 : : #include "utils/freepage.h"
59 : : #include "utils/memutils.h"
60 : : #include "utils/resowner.h"
61 : :
62 : : /*
63 : : * How many segments to create before we double the segment size. If this is
64 : : * low, then there is likely to be a lot of wasted space in the largest
65 : : * segment. If it is high, then we risk running out of segment slots (see
66 : : * dsm.c's limits on total number of segments), or limiting the total size
67 : : * an area can manage when using small pointers.
68 : : */
69 : : #define DSA_NUM_SEGMENTS_AT_EACH_SIZE 2
70 : :
71 : : /*
72 : : * The maximum number of DSM segments that an area can own, determined by
73 : : * the number of bits remaining (but capped at 1024).
74 : : */
75 : : #define DSA_MAX_SEGMENTS \
76 : : Min(1024, (1 << ((SIZEOF_DSA_POINTER * 8) - DSA_OFFSET_WIDTH)))
77 : :
78 : : /* The bitmask for extracting the offset from a dsa_pointer. */
79 : : #define DSA_OFFSET_BITMASK (((dsa_pointer) 1 << DSA_OFFSET_WIDTH) - 1)
80 : :
81 : : /* Number of pages (see FPM_PAGE_SIZE) per regular superblock. */
82 : : #define DSA_PAGES_PER_SUPERBLOCK 16
83 : :
84 : : /*
85 : : * A magic number used as a sanity check for following DSM segments belonging
86 : : * to a DSA area (this number will be XORed with the area handle and
87 : : * the segment index).
88 : : */
89 : : #define DSA_SEGMENT_HEADER_MAGIC 0x0ce26608
90 : :
91 : : /* Build a dsa_pointer given a segment number and offset. */
92 : : #define DSA_MAKE_POINTER(segment_number, offset) \
93 : : (((dsa_pointer) (segment_number) << DSA_OFFSET_WIDTH) | (offset))
94 : :
95 : : /* Extract the segment number from a dsa_pointer. */
96 : : #define DSA_EXTRACT_SEGMENT_NUMBER(dp) ((dp) >> DSA_OFFSET_WIDTH)
97 : :
98 : : /* Extract the offset from a dsa_pointer. */
99 : : #define DSA_EXTRACT_OFFSET(dp) ((dp) & DSA_OFFSET_BITMASK)
100 : :
101 : : /* The type used for index segment indexes (zero based). */
102 : : typedef size_t dsa_segment_index;
103 : :
104 : : /* Sentinel value for dsa_segment_index indicating 'none' or 'end'. */
105 : : #define DSA_SEGMENT_INDEX_NONE (~(dsa_segment_index)0)
106 : :
107 : : /*
108 : : * How many bins of segments do we have? The bins are used to categorize
109 : : * segments by their largest contiguous run of free pages.
110 : : */
111 : : #define DSA_NUM_SEGMENT_BINS 16
112 : :
113 : : /*
114 : : * What is the lowest bin that holds segments that *might* have n contiguous
115 : : * free pages? There is no point in looking in segments in lower bins; they
116 : : * definitely can't service a request for n free pages.
117 : : */
118 : : static inline size_t
632 tmunro@postgresql.or 119 :CBC 18909 : contiguous_pages_to_segment_bin(size_t n)
120 : : {
121 : : size_t bin;
122 : :
123 [ + + ]: 18909 : if (n == 0)
124 : 664 : bin = 0;
125 : : else
126 : 18245 : bin = pg_leftmost_one_pos_size_t(n) + 1;
127 : :
128 : 18909 : return Min(bin, DSA_NUM_SEGMENT_BINS - 1);
129 : : }
130 : :
131 : : /* Macros for access to locks. */
132 : : #define DSA_AREA_LOCK(area) (&area->control->lock)
133 : : #define DSA_SCLASS_LOCK(area, sclass) (&area->control->pools[sclass].lock)
134 : :
135 : : /*
136 : : * The header for an individual segment. This lives at the start of each DSM
137 : : * segment owned by a DSA area including the first segment (where it appears
138 : : * as part of the dsa_area_control struct).
139 : : */
140 : : typedef struct
141 : : {
142 : : /* Sanity check magic value. */
143 : : uint32 magic;
144 : : /* Total number of pages in this segment (excluding metadata area). */
145 : : size_t usable_pages;
146 : : /* Total size of this segment in bytes. */
147 : : size_t size;
148 : :
149 : : /*
150 : : * Index of the segment that precedes this one in the same segment bin, or
151 : : * DSA_SEGMENT_INDEX_NONE if this is the first one.
152 : : */
153 : : dsa_segment_index prev;
154 : :
155 : : /*
156 : : * Index of the segment that follows this one in the same segment bin, or
157 : : * DSA_SEGMENT_INDEX_NONE if this is the last one.
158 : : */
159 : : dsa_segment_index next;
160 : : /* The index of the bin that contains this segment. */
161 : : size_t bin;
162 : :
163 : : /*
164 : : * A flag raised to indicate that this segment is being returned to the
165 : : * operating system and has been unpinned.
166 : : */
167 : : bool freed;
168 : : } dsa_segment_header;
169 : :
170 : : /*
171 : : * Metadata for one superblock.
172 : : *
173 : : * For most blocks, span objects are stored out-of-line; that is, the span
174 : : * object is not stored within the block itself. But, as an exception, for a
175 : : * "span of spans", the span object is stored "inline". The allocation is
176 : : * always exactly one page, and the dsa_area_span object is located at
177 : : * the beginning of that page. The size class is DSA_SCLASS_BLOCK_OF_SPANS,
178 : : * and the remaining fields are used just as they would be in an ordinary
179 : : * block. We can't allocate spans out of ordinary superblocks because
180 : : * creating an ordinary superblock requires us to be able to allocate a span
181 : : * *first*. Doing it this way avoids that circularity.
182 : : */
183 : : typedef struct
184 : : {
185 : : dsa_pointer pool; /* Containing pool. */
186 : : dsa_pointer prevspan; /* Previous span. */
187 : : dsa_pointer nextspan; /* Next span. */
188 : : dsa_pointer start; /* Starting address. */
189 : : size_t npages; /* Length of span in pages. */
190 : : uint16 size_class; /* Size class. */
191 : : uint16 ninitialized; /* Maximum number of objects ever allocated. */
192 : : uint16 nallocatable; /* Number of objects currently allocatable. */
193 : : uint16 firstfree; /* First object on free list. */
194 : : uint16 nmax; /* Maximum number of objects ever possible. */
195 : : uint16 fclass; /* Current fullness class. */
196 : : } dsa_area_span;
197 : :
198 : : /*
199 : : * Given a pointer to an object in a span, access the index of the next free
200 : : * object in the same span (ie in the span's freelist) as an L-value.
201 : : */
202 : : #define NextFreeObjectIndex(object) (* (uint16 *) (object))
203 : :
204 : : /*
205 : : * Small allocations are handled by dividing a single block of memory into
206 : : * many small objects of equal size. The possible allocation sizes are
207 : : * defined by the following array. Larger size classes are spaced more widely
208 : : * than smaller size classes. We fudge the spacing for size classes >1kB to
209 : : * avoid space wastage: based on the knowledge that we plan to allocate 64kB
210 : : * blocks, we bump the maximum object size up to the largest multiple of
211 : : * 8 bytes that still lets us fit the same number of objects into one block.
212 : : *
213 : : * NB: Because of this fudging, if we were ever to use differently-sized blocks
214 : : * for small allocations, these size classes would need to be reworked to be
215 : : * optimal for the new size.
216 : : *
217 : : * NB: The optimal spacing for size classes, as well as the size of the blocks
218 : : * out of which small objects are allocated, is not a question that has one
219 : : * right answer. Some allocators (such as tcmalloc) use more closely-spaced
220 : : * size classes than we do here, while others (like aset.c) use more
221 : : * widely-spaced classes. Spacing the classes more closely avoids wasting
222 : : * memory within individual chunks, but also means a larger number of
223 : : * potentially-unfilled blocks.
224 : : */
225 : : static const uint16 dsa_size_classes[] = {
226 : : sizeof(dsa_area_span), 0, /* special size classes */
227 : : 8, 16, 24, 32, 40, 48, 56, 64, /* 8 classes separated by 8 bytes */
228 : : 80, 96, 112, 128, /* 4 classes separated by 16 bytes */
229 : : 160, 192, 224, 256, /* 4 classes separated by 32 bytes */
230 : : 320, 384, 448, 512, /* 4 classes separated by 64 bytes */
231 : : 640, 768, 896, 1024, /* 4 classes separated by 128 bytes */
232 : : 1280, 1560, 1816, 2048, /* 4 classes separated by ~256 bytes */
233 : : 2616, 3120, 3640, 4096, /* 4 classes separated by ~512 bytes */
234 : : 5456, 6552, 7280, 8192 /* 4 classes separated by ~1024 bytes */
235 : : };
236 : : #define DSA_NUM_SIZE_CLASSES lengthof(dsa_size_classes)
237 : :
238 : : /* Special size classes. */
239 : : #define DSA_SCLASS_BLOCK_OF_SPANS 0
240 : : #define DSA_SCLASS_SPAN_LARGE 1
241 : :
242 : : /*
243 : : * The following lookup table is used to map the size of small objects
244 : : * (less than 1kB) onto the corresponding size class. To use this table,
245 : : * round the size of the object up to the next multiple of 8 bytes, and then
246 : : * index into this array.
247 : : */
248 : : static const uint8 dsa_size_class_map[] = {
249 : : 2, 3, 4, 5, 6, 7, 8, 9, 10, 10, 11, 11, 12, 12, 13, 13,
250 : : 14, 14, 14, 14, 15, 15, 15, 15, 16, 16, 16, 16, 17, 17, 17, 17,
251 : : 18, 18, 18, 18, 18, 18, 18, 18, 19, 19, 19, 19, 19, 19, 19, 19,
252 : : 20, 20, 20, 20, 20, 20, 20, 20, 21, 21, 21, 21, 21, 21, 21, 21,
253 : : 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22,
254 : : 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23,
255 : : 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
256 : : 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25
257 : : };
258 : : #define DSA_SIZE_CLASS_MAP_QUANTUM 8
259 : :
260 : : /*
261 : : * Superblocks are binned by how full they are. Generally, each fullness
262 : : * class corresponds to one quartile, but the block being used for
263 : : * allocations is always at the head of the list for fullness class 1,
264 : : * regardless of how full it really is.
265 : : */
266 : : #define DSA_FULLNESS_CLASSES 4
267 : :
268 : : /*
269 : : * A dsa_area_pool represents a set of objects of a given size class.
270 : : *
271 : : * Perhaps there should be multiple pools for the same size class for
272 : : * contention avoidance, but for now there is just one!
273 : : */
274 : : typedef struct
275 : : {
276 : : /* A lock protecting access to this pool. */
277 : : LWLock lock;
278 : : /* A set of linked lists of spans, arranged by fullness. */
279 : : dsa_pointer spans[DSA_FULLNESS_CLASSES];
280 : : /* Should we pad this out to a cacheline boundary? */
281 : : } dsa_area_pool;
282 : :
283 : : /*
284 : : * The control block for an area. This lives in shared memory, at the start of
285 : : * the first DSM segment controlled by this area.
286 : : */
287 : : typedef struct
288 : : {
289 : : /* The segment header for the first segment. */
290 : : dsa_segment_header segment_header;
291 : : /* The handle for this area. */
292 : : dsa_handle handle;
293 : : /* The handles of the segments owned by this area. */
294 : : dsm_handle segment_handles[DSA_MAX_SEGMENTS];
295 : : /* Lists of segments, binned by maximum contiguous run of free pages. */
296 : : dsa_segment_index segment_bins[DSA_NUM_SEGMENT_BINS];
297 : : /* The object pools for each size class. */
298 : : dsa_area_pool pools[DSA_NUM_SIZE_CLASSES];
299 : : /* initial allocation segment size */
300 : : size_t init_segment_size;
301 : : /* maximum allocation segment size */
302 : : size_t max_segment_size;
303 : : /* The total size of all active segments. */
304 : : size_t total_segment_size;
305 : : /* The maximum total size of backing storage we are allowed. */
306 : : size_t max_total_segment_size;
307 : : /* Highest used segment index in the history of this area. */
308 : : dsa_segment_index high_segment_index;
309 : : /* The reference count for this area. */
310 : : int refcnt;
311 : : /* A flag indicating that this area has been pinned. */
312 : : bool pinned;
313 : : /* The number of times that segments have been freed. */
314 : : size_t freed_segment_counter;
315 : : /* The LWLock tranche ID. */
316 : : int lwlock_tranche_id;
317 : : /* The general lock (protects everything except object pools). */
318 : : LWLock lock;
319 : : } dsa_area_control;
320 : :
321 : : /* Given a pointer to a pool, find a dsa_pointer. */
322 : : #define DsaAreaPoolToDsaPointer(area, p) \
323 : : DSA_MAKE_POINTER(0, (char *) p - (char *) area->control)
324 : :
325 : : /*
326 : : * A dsa_segment_map is stored within the backend-private memory of each
327 : : * individual backend. It holds the base address of the segment within that
328 : : * backend, plus the addresses of key objects within the segment. Those
329 : : * could instead be derived from the base address but it's handy to have them
330 : : * around.
331 : : */
332 : : typedef struct
333 : : {
334 : : dsm_segment *segment; /* DSM segment */
335 : : char *mapped_address; /* Address at which segment is mapped */
336 : : dsa_segment_header *header; /* Header (same as mapped_address) */
337 : : FreePageManager *fpm; /* Free page manager within segment. */
338 : : dsa_pointer *pagemap; /* Page map within segment. */
339 : : } dsa_segment_map;
340 : :
341 : : /*
342 : : * Per-backend state for a storage area. Backends obtain one of these by
343 : : * creating an area or attaching to an existing one using a handle. Each
344 : : * process that needs to use an area uses its own object to track where the
345 : : * segments are mapped.
346 : : */
347 : : struct dsa_area
348 : : {
349 : : /* Pointer to the control object in shared memory. */
350 : : dsa_area_control *control;
351 : :
352 : : /*
353 : : * All the mappings are owned by this. The dsa_area itself is not
354 : : * directly tracked by the ResourceOwner, but the effect is the same. NULL
355 : : * if the attachment has session lifespan, i.e if dsa_pin_mapping() has
356 : : * been called.
357 : : */
358 : : ResourceOwner resowner;
359 : :
360 : : /*
361 : : * This backend's array of segment maps, ordered by segment index
362 : : * corresponding to control->segment_handles. Some of the area's segments
363 : : * may not be mapped in this backend yet, and some slots may have been
364 : : * freed and need to be detached; these operations happen on demand.
365 : : */
366 : : dsa_segment_map segment_maps[DSA_MAX_SEGMENTS];
367 : :
368 : : /* The highest segment index this backend has ever mapped. */
369 : : dsa_segment_index high_segment_index;
370 : :
371 : : /* The last observed freed_segment_counter. */
372 : : size_t freed_segment_counter;
373 : : };
374 : :
375 : : #define DSA_SPAN_NOTHING_FREE ((uint16) -1)
376 : : #define DSA_SUPERBLOCK_SIZE (DSA_PAGES_PER_SUPERBLOCK * FPM_PAGE_SIZE)
377 : :
378 : : /* Given a pointer to a segment_map, obtain a segment index number. */
379 : : #define get_segment_index(area, segment_map_ptr) \
380 : : (segment_map_ptr - &area->segment_maps[0])
381 : :
382 : : static void init_span(dsa_area *area, dsa_pointer span_pointer,
383 : : dsa_area_pool *pool, dsa_pointer start, size_t npages,
384 : : uint16 size_class);
385 : : static bool transfer_first_span(dsa_area *area, dsa_area_pool *pool,
386 : : int fromclass, int toclass);
387 : : static inline dsa_pointer alloc_object(dsa_area *area, int size_class);
388 : : static bool ensure_active_superblock(dsa_area *area, dsa_area_pool *pool,
389 : : int size_class);
390 : : static dsa_segment_map *get_segment_by_index(dsa_area *area,
391 : : dsa_segment_index index);
392 : : static void destroy_superblock(dsa_area *area, dsa_pointer span_pointer);
393 : : static void unlink_span(dsa_area *area, dsa_area_span *span);
394 : : static void add_span_to_fullness_class(dsa_area *area, dsa_area_span *span,
395 : : dsa_pointer span_pointer, int fclass);
396 : : static void unlink_segment(dsa_area *area, dsa_segment_map *segment_map);
397 : : static dsa_segment_map *get_best_segment(dsa_area *area, size_t npages);
398 : : static dsa_segment_map *make_new_segment(dsa_area *area, size_t requested_pages);
399 : : static dsa_area *create_internal(void *place, size_t size,
400 : : int tranche_id,
401 : : dsm_handle control_handle,
402 : : dsm_segment *control_segment,
403 : : size_t init_segment_size,
404 : : size_t max_segment_size);
405 : : static dsa_area *attach_internal(void *place, dsm_segment *segment,
406 : : dsa_handle handle);
407 : : static void check_for_freed_segments(dsa_area *area);
408 : : static void check_for_freed_segments_locked(dsa_area *area);
409 : : static void rebin_segment(dsa_area *area, dsa_segment_map *segment_map);
410 : :
411 : : /*
412 : : * Create a new shared area in a new DSM segment. Further DSM segments will
413 : : * be allocated as required to extend the available space.
414 : : *
415 : : * We can't allocate a LWLock tranche_id within this function, because tranche
416 : : * IDs are a scarce resource; there are only 64k available, using low numbers
417 : : * when possible matters, and we have no provision for recycling them. So,
418 : : * we require the caller to provide one.
419 : : */
420 : : dsa_area *
18 msawada@postgresql.o 421 :GNC 87 : dsa_create_ext(int tranche_id, size_t init_segment_size, size_t max_segment_size)
422 : : {
423 : : dsm_segment *segment;
424 : : dsa_area *area;
425 : :
426 : : /*
427 : : * Create the DSM segment that will hold the shared control object and the
428 : : * first segment of usable space.
429 : : */
430 : 87 : segment = dsm_create(init_segment_size, 0);
431 : :
432 : : /*
433 : : * All segments backing this area are pinned, so that DSA can explicitly
434 : : * control their lifetime (otherwise a newly created segment belonging to
435 : : * this area might be freed when the only backend that happens to have it
436 : : * mapped in ends, corrupting the area).
437 : : */
2690 rhaas@postgresql.org 438 :CBC 87 : dsm_pin_segment(segment);
439 : :
440 : : /* Create a new DSA area with the control object in this segment. */
441 : 87 : area = create_internal(dsm_segment_address(segment),
442 : : init_segment_size,
443 : : tranche_id,
444 : : dsm_segment_handle(segment), segment,
445 : : init_segment_size, max_segment_size);
446 : :
447 : : /* Clean up when the control segment detaches. */
448 : 87 : on_dsm_detach(segment, &dsa_on_dsm_detach_release_in_place,
449 : 87 : PointerGetDatum(dsm_segment_address(segment)));
450 : :
451 : 87 : return area;
452 : : }
453 : :
454 : : /*
455 : : * Create a new shared area in an existing shared memory space, which may be
456 : : * either DSM or Postmaster-initialized memory. DSM segments will be
457 : : * allocated as required to extend the available space, though that can be
458 : : * prevented with dsa_set_size_limit(area, size) using the same size provided
459 : : * to dsa_create_in_place.
460 : : *
461 : : * Areas created in-place must eventually be released by the backend that
462 : : * created them and all backends that attach to them. This can be done
463 : : * explicitly with dsa_release_in_place, or, in the special case that 'place'
464 : : * happens to be in a pre-existing DSM segment, by passing in a pointer to the
465 : : * segment so that a detach hook can be registered with the containing DSM
466 : : * segment.
467 : : *
468 : : * See dsa_create() for a note about the tranche arguments.
469 : : */
470 : : dsa_area *
18 msawada@postgresql.o 471 :GNC 1289 : dsa_create_in_place_ext(void *place, size_t size,
472 : : int tranche_id, dsm_segment *segment,
473 : : size_t init_segment_size, size_t max_segment_size)
474 : : {
475 : : dsa_area *area;
476 : :
2656 rhaas@postgresql.org 477 :CBC 1289 : area = create_internal(place, size, tranche_id,
478 : : DSM_HANDLE_INVALID, NULL,
479 : : init_segment_size, max_segment_size);
480 : :
481 : : /*
482 : : * Clean up when the control segment detaches, if a containing DSM segment
483 : : * was provided.
484 : : */
2690 485 [ + + ]: 1289 : if (segment != NULL)
486 : 391 : on_dsm_detach(segment, &dsa_on_dsm_detach_release_in_place,
487 : : PointerGetDatum(place));
488 : :
489 : 1289 : return area;
490 : : }
491 : :
492 : : /*
493 : : * Obtain a handle that can be passed to other processes so that they can
494 : : * attach to the given area. Cannot be called for areas created with
495 : : * dsa_create_in_place.
496 : : */
497 : : dsa_handle
498 : 84 : dsa_get_handle(dsa_area *area)
499 : : {
445 tgl@sss.pgh.pa.us 500 [ - + ]: 84 : Assert(area->control->handle != DSA_HANDLE_INVALID);
2690 rhaas@postgresql.org 501 : 84 : return area->control->handle;
502 : : }
503 : :
504 : : /*
505 : : * Attach to an area given a handle generated (possibly in another process) by
506 : : * dsa_get_handle. The area must have been created with dsa_create (not
507 : : * dsa_create_in_place).
508 : : */
509 : : dsa_area *
510 : 126 : dsa_attach(dsa_handle handle)
511 : : {
512 : : dsm_segment *segment;
513 : : dsa_area *area;
514 : :
515 : : /*
516 : : * An area handle is really a DSM segment handle for the first segment, so
517 : : * we go ahead and attach to that.
518 : : */
519 : 126 : segment = dsm_attach(handle);
520 [ - + ]: 126 : if (segment == NULL)
2690 rhaas@postgresql.org 521 [ # # ]:UBC 0 : ereport(ERROR,
522 : : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
523 : : errmsg("could not attach to dynamic shared area")));
524 : :
2690 rhaas@postgresql.org 525 :CBC 126 : area = attach_internal(dsm_segment_address(segment), segment, handle);
526 : :
527 : : /* Clean up when the control segment detaches. */
528 : 126 : on_dsm_detach(segment, &dsa_on_dsm_detach_release_in_place,
529 : 126 : PointerGetDatum(dsm_segment_address(segment)));
530 : :
531 : 126 : return area;
532 : : }
533 : :
534 : : /*
535 : : * Attach to an area that was created with dsa_create_in_place. The caller
536 : : * must somehow know the location in memory that was used when the area was
537 : : * created, though it may be mapped at a different virtual address in this
538 : : * process.
539 : : *
540 : : * See dsa_create_in_place for note about releasing in-place areas, and the
541 : : * optional 'segment' argument which can be provided to allow automatic
542 : : * release if the containing memory happens to be a DSM segment.
543 : : */
544 : : dsa_area *
545 : 22256 : dsa_attach_in_place(void *place, dsm_segment *segment)
546 : : {
547 : : dsa_area *area;
548 : :
445 tgl@sss.pgh.pa.us 549 : 22256 : area = attach_internal(place, NULL, DSA_HANDLE_INVALID);
550 : :
551 : : /*
552 : : * Clean up when the control segment detaches, if a containing DSM segment
553 : : * was provided.
554 : : */
2690 rhaas@postgresql.org 555 [ + + ]: 22256 : if (segment != NULL)
556 : 2554 : on_dsm_detach(segment, &dsa_on_dsm_detach_release_in_place,
557 : : PointerGetDatum(place));
558 : :
559 : 22256 : return area;
560 : : }
561 : :
562 : : /*
563 : : * Release a DSA area that was produced by dsa_create_in_place or
564 : : * dsa_attach_in_place. The 'segment' argument is ignored but provides an
565 : : * interface suitable for on_dsm_detach, for the convenience of users who want
566 : : * to create a DSA segment inside an existing DSM segment and have it
567 : : * automatically released when the containing DSM segment is detached.
568 : : * 'place' should be the address of the place where the area was created.
569 : : *
570 : : * This callback is automatically registered for the DSM segment containing
571 : : * the control object of in-place areas when a segment is provided to
572 : : * dsa_create_in_place or dsa_attach_in_place, and also for all areas created
573 : : * with dsa_create.
574 : : */
575 : : void
576 : 3138 : dsa_on_dsm_detach_release_in_place(dsm_segment *segment, Datum place)
577 : : {
578 : 3138 : dsa_release_in_place(DatumGetPointer(place));
579 : 3138 : }
580 : :
581 : : /*
582 : : * Release a DSA area that was produced by dsa_create_in_place or
583 : : * dsa_attach_in_place. The 'code' argument is ignored but provides an
584 : : * interface suitable for on_shmem_exit or before_shmem_exit, for the
585 : : * convenience of users who want to create a DSA segment inside shared memory
586 : : * other than a DSM segment and have it automatically release at backend exit.
587 : : * 'place' should be the address of the place where the area was created.
588 : : */
589 : : void
2690 rhaas@postgresql.org 590 :UBC 0 : dsa_on_shmem_exit_release_in_place(int code, Datum place)
591 : : {
592 : 0 : dsa_release_in_place(DatumGetPointer(place));
593 : 0 : }
594 : :
595 : : /*
596 : : * Release a DSA area that was produced by dsa_create_in_place or
597 : : * dsa_attach_in_place. It is preferable to use one of the 'dsa_on_XXX'
598 : : * callbacks so that this is managed automatically, because failure to release
599 : : * an area created in-place leaks its segments permanently.
600 : : *
601 : : * This is also called automatically for areas produced by dsa_create or
602 : : * dsa_attach as an implementation detail.
603 : : */
604 : : void
2690 rhaas@postgresql.org 605 :CBC 3138 : dsa_release_in_place(void *place)
606 : : {
607 : 3138 : dsa_area_control *control = (dsa_area_control *) place;
608 : : int i;
609 : :
610 : 3138 : LWLockAcquire(&control->lock, LW_EXCLUSIVE);
611 [ - + ]: 3138 : Assert(control->segment_header.magic ==
612 : : (DSA_SEGMENT_HEADER_MAGIC ^ control->handle ^ 0));
613 [ - + ]: 3138 : Assert(control->refcnt > 0);
614 [ + + ]: 3138 : if (--control->refcnt == 0)
615 : : {
616 [ + + ]: 937 : for (i = 0; i <= control->high_segment_index; ++i)
617 : : {
618 : : dsm_handle handle;
619 : :
620 : 530 : handle = control->segment_handles[i];
621 [ + + ]: 530 : if (handle != DSM_HANDLE_INVALID)
622 : 139 : dsm_unpin_segment(handle);
623 : : }
624 : : }
625 : 3138 : LWLockRelease(&control->lock);
626 : 3138 : }
627 : :
628 : : /*
629 : : * Keep a DSA area attached until end of session or explicit detach.
630 : : *
631 : : * By default, areas are owned by the current resource owner, which means they
632 : : * are detached automatically when that scope ends.
633 : : */
634 : : void
635 : 21265 : dsa_pin_mapping(dsa_area *area)
636 : : {
637 : : int i;
638 : :
151 heikki.linnakangas@i 639 [ + + ]:GNC 21265 : if (area->resowner != NULL)
640 : : {
641 : 1487 : area->resowner = NULL;
642 : :
643 [ + + ]: 2984 : for (i = 0; i <= area->high_segment_index; ++i)
644 [ + + ]: 1497 : if (area->segment_maps[i].segment != NULL)
645 : 116 : dsm_pin_mapping(area->segment_maps[i].segment);
646 : : }
2690 rhaas@postgresql.org 647 :CBC 21265 : }
648 : :
649 : : /*
650 : : * Allocate memory in this storage area. The return value is a dsa_pointer
651 : : * that can be passed to other processes, and converted to a local pointer
652 : : * with dsa_get_address. 'flags' is a bitmap which should be constructed
653 : : * from the following values:
654 : : *
655 : : * DSA_ALLOC_HUGE allows allocations >= 1GB. Otherwise, such allocations
656 : : * will result in an ERROR.
657 : : *
658 : : * DSA_ALLOC_NO_OOM causes this function to return InvalidDsaPointer when
659 : : * no memory is available or a size limit established by dsa_set_size_limit
660 : : * would be exceeded. Otherwise, such allocations will result in an ERROR.
661 : : *
662 : : * DSA_ALLOC_ZERO causes the allocated memory to be zeroed. Otherwise, the
663 : : * contents of newly-allocated memory are indeterminate.
664 : : *
665 : : * These flags correspond to similarly named flags used by
666 : : * MemoryContextAllocExtended(). See also the macros dsa_allocate and
667 : : * dsa_allocate0 which expand to a call to this function with commonly used
668 : : * flags.
669 : : */
670 : : dsa_pointer
2031 tmunro@postgresql.or 671 : 505407 : dsa_allocate_extended(dsa_area *area, size_t size, int flags)
672 : : {
673 : : uint16 size_class;
674 : : dsa_pointer start_pointer;
675 : : dsa_segment_map *segment_map;
676 : : dsa_pointer result;
677 : :
2690 rhaas@postgresql.org 678 [ - + ]: 505407 : Assert(size > 0);
679 : :
680 : : /* Sanity check on huge individual allocation size. */
2611 681 [ + + + - ]: 505407 : if (((flags & DSA_ALLOC_HUGE) != 0 && !AllocHugeSizeIsValid(size)) ||
682 [ + + - + ]: 505407 : ((flags & DSA_ALLOC_HUGE) == 0 && !AllocSizeIsValid(size)))
2611 rhaas@postgresql.org 683 [ # # ]:UBC 0 : elog(ERROR, "invalid DSA memory alloc request size %zu", size);
684 : :
685 : : /*
686 : : * If bigger than the largest size class, just grab a run of pages from
687 : : * the free page manager, instead of allocating an object from a pool.
688 : : * There will still be a span, but it's a special class of span that
689 : : * manages this whole allocation and simply gives all pages back to the
690 : : * free page manager when dsa_free is called.
691 : : */
2690 rhaas@postgresql.org 692 [ + + ]:CBC 505407 : if (size > dsa_size_classes[lengthof(dsa_size_classes) - 1])
693 : : {
2031 tmunro@postgresql.or 694 : 2414 : size_t npages = fpm_size_to_pages(size);
695 : : size_t first_page;
696 : : dsa_pointer span_pointer;
2690 rhaas@postgresql.org 697 : 2414 : dsa_area_pool *pool = &area->control->pools[DSA_SCLASS_SPAN_LARGE];
698 : :
699 : : /* Obtain a span object. */
700 : 2414 : span_pointer = alloc_object(area, DSA_SCLASS_BLOCK_OF_SPANS);
701 [ - + ]: 2414 : if (!DsaPointerIsValid(span_pointer))
702 : : {
703 : : /* Raise error unless asked not to. */
1875 tmunro@postgresql.or 704 [ # # ]:UBC 0 : if ((flags & DSA_ALLOC_NO_OOM) == 0)
705 [ # # ]: 0 : ereport(ERROR,
706 : : (errcode(ERRCODE_OUT_OF_MEMORY),
707 : : errmsg("out of memory"),
708 : : errdetail("Failed on DSA request of size %zu.",
709 : : size)));
2690 rhaas@postgresql.org 710 : 0 : return InvalidDsaPointer;
711 : : }
712 : :
2690 rhaas@postgresql.org 713 :CBC 2414 : LWLockAcquire(DSA_AREA_LOCK(area), LW_EXCLUSIVE);
714 : :
715 : : /* Find a segment from which to allocate. */
716 : 2414 : segment_map = get_best_segment(area, npages);
717 [ + + ]: 2414 : if (segment_map == NULL)
718 : 19 : segment_map = make_new_segment(area, npages);
719 [ - + ]: 2414 : if (segment_map == NULL)
720 : : {
721 : : /* Can't make any more segments: game over. */
2690 rhaas@postgresql.org 722 :UBC 0 : LWLockRelease(DSA_AREA_LOCK(area));
723 : 0 : dsa_free(area, span_pointer);
724 : :
725 : : /* Raise error unless asked not to. */
2425 andres@anarazel.de 726 [ # # ]: 0 : if ((flags & DSA_ALLOC_NO_OOM) == 0)
2611 rhaas@postgresql.org 727 [ # # ]: 0 : ereport(ERROR,
728 : : (errcode(ERRCODE_OUT_OF_MEMORY),
729 : : errmsg("out of memory"),
730 : : errdetail("Failed on DSA request of size %zu.",
731 : : size)));
2690 732 : 0 : return InvalidDsaPointer;
733 : : }
734 : :
735 : : /*
736 : : * Ask the free page manager for a run of pages. This should always
737 : : * succeed, since both get_best_segment and make_new_segment should
738 : : * only return a non-NULL pointer if it actually contains enough
739 : : * contiguous freespace. If it does fail, something in our backend
740 : : * private state is out of whack, so use FATAL to kill the process.
741 : : */
2690 rhaas@postgresql.org 742 [ - + ]:CBC 2414 : if (!FreePageManagerGet(segment_map->fpm, npages, &first_page))
2690 rhaas@postgresql.org 743 [ # # ]:UBC 0 : elog(FATAL,
744 : : "dsa_allocate could not find %zu free pages", npages);
2690 rhaas@postgresql.org 745 :CBC 2414 : LWLockRelease(DSA_AREA_LOCK(area));
746 : :
747 : 2414 : start_pointer = DSA_MAKE_POINTER(get_segment_index(area, segment_map),
748 : : first_page * FPM_PAGE_SIZE);
749 : :
750 : : /* Initialize span and pagemap. */
751 : 2414 : LWLockAcquire(DSA_SCLASS_LOCK(area, DSA_SCLASS_SPAN_LARGE),
752 : : LW_EXCLUSIVE);
753 : 2414 : init_span(area, span_pointer, pool, start_pointer, npages,
754 : : DSA_SCLASS_SPAN_LARGE);
755 : 2414 : segment_map->pagemap[first_page] = span_pointer;
756 : 2414 : LWLockRelease(DSA_SCLASS_LOCK(area, DSA_SCLASS_SPAN_LARGE));
757 : :
758 : : /* Zero-initialize the memory if requested. */
2611 759 [ + + ]: 2414 : if ((flags & DSA_ALLOC_ZERO) != 0)
760 : 183 : memset(dsa_get_address(area, start_pointer), 0, size);
761 : :
2690 762 : 2414 : return start_pointer;
763 : : }
764 : :
765 : : /* Map allocation to a size class. */
766 [ + + ]: 502993 : if (size < lengthof(dsa_size_class_map) * DSA_SIZE_CLASS_MAP_QUANTUM)
767 : : {
768 : : int mapidx;
769 : :
770 : : /* For smaller sizes we have a lookup table... */
771 : 498588 : mapidx = ((size + DSA_SIZE_CLASS_MAP_QUANTUM - 1) /
772 : 498588 : DSA_SIZE_CLASS_MAP_QUANTUM) - 1;
773 : 498588 : size_class = dsa_size_class_map[mapidx];
774 : : }
775 : : else
776 : : {
777 : : uint16 min;
778 : : uint16 max;
779 : :
780 : : /* ... and for the rest we search by binary chop. */
781 : 4405 : min = dsa_size_class_map[lengthof(dsa_size_class_map) - 1];
782 : 4405 : max = lengthof(dsa_size_classes) - 1;
783 : :
784 [ + + ]: 20333 : while (min < max)
785 : : {
786 : 15928 : uint16 mid = (min + max) / 2;
787 : 15928 : uint16 class_size = dsa_size_classes[mid];
788 : :
789 [ + + ]: 15928 : if (class_size < size)
790 : 6373 : min = mid + 1;
791 : : else
792 : 9555 : max = mid;
793 : : }
794 : :
795 : 4405 : size_class = min;
796 : : }
797 [ - + ]: 502993 : Assert(size <= dsa_size_classes[size_class]);
798 [ + - - + ]: 502993 : Assert(size_class == 0 || size > dsa_size_classes[size_class - 1]);
799 : :
800 : : /* Attempt to allocate an object from the appropriate pool. */
2611 801 : 502993 : result = alloc_object(area, size_class);
802 : :
803 : : /* Check for failure to allocate. */
804 [ - + ]: 502993 : if (!DsaPointerIsValid(result))
805 : : {
806 : : /* Raise error unless asked not to. */
2611 rhaas@postgresql.org 807 [ # # ]:UBC 0 : if ((flags & DSA_ALLOC_NO_OOM) == 0)
808 [ # # ]: 0 : ereport(ERROR,
809 : : (errcode(ERRCODE_OUT_OF_MEMORY),
810 : : errmsg("out of memory"),
811 : : errdetail("Failed on DSA request of size %zu.", size)));
812 : 0 : return InvalidDsaPointer;
813 : : }
814 : :
815 : : /* Zero-initialize the memory if requested. */
2611 rhaas@postgresql.org 816 [ + + ]:CBC 502993 : if ((flags & DSA_ALLOC_ZERO) != 0)
817 : 247193 : memset(dsa_get_address(area, result), 0, size);
818 : :
819 : 502993 : return result;
820 : : }
821 : :
822 : : /*
823 : : * Free memory obtained with dsa_allocate.
824 : : */
825 : : void
2690 826 : 74428 : dsa_free(dsa_area *area, dsa_pointer dp)
827 : : {
828 : : dsa_segment_map *segment_map;
829 : : int pageno;
830 : : dsa_pointer span_pointer;
831 : : dsa_area_span *span;
832 : : char *superblock;
833 : : char *object;
834 : : size_t size;
835 : : int size_class;
836 : :
837 : : /* Make sure we don't have a stale segment in the slot 'dp' refers to. */
838 : 74428 : check_for_freed_segments(area);
839 : :
840 : : /* Locate the object, span and pool. */
841 : 74428 : segment_map = get_segment_by_index(area, DSA_EXTRACT_SEGMENT_NUMBER(dp));
842 : 74428 : pageno = DSA_EXTRACT_OFFSET(dp) / FPM_PAGE_SIZE;
843 : 74428 : span_pointer = segment_map->pagemap[pageno];
844 : 74428 : span = dsa_get_address(area, span_pointer);
845 : 74428 : superblock = dsa_get_address(area, span->start);
846 : 74428 : object = dsa_get_address(area, dp);
847 : 74428 : size_class = span->size_class;
848 : 74428 : size = dsa_size_classes[size_class];
849 : :
850 : : /*
851 : : * Special case for large objects that live in a special span: we return
852 : : * those pages directly to the free page manager and free the span.
853 : : */
854 [ + + ]: 74428 : if (span->size_class == DSA_SCLASS_SPAN_LARGE)
855 : : {
856 : :
857 : : #ifdef CLOBBER_FREED_MEMORY
858 : 2321 : memset(object, 0x7f, span->npages * FPM_PAGE_SIZE);
859 : : #endif
860 : :
861 : : /* Give pages back to free page manager. */
862 : 2321 : LWLockAcquire(DSA_AREA_LOCK(area), LW_EXCLUSIVE);
863 : 2321 : FreePageManagerPut(segment_map->fpm,
864 : 2321 : DSA_EXTRACT_OFFSET(span->start) / FPM_PAGE_SIZE,
865 : : span->npages);
866 : :
867 : : /* Move segment to appropriate bin if necessary. */
285 tmunro@postgresql.or 868 : 2321 : rebin_segment(area, segment_map);
2690 rhaas@postgresql.org 869 : 2321 : LWLockRelease(DSA_AREA_LOCK(area));
870 : :
871 : : /* Unlink span. */
872 : 2321 : LWLockAcquire(DSA_SCLASS_LOCK(area, DSA_SCLASS_SPAN_LARGE),
873 : : LW_EXCLUSIVE);
874 : 2321 : unlink_span(area, span);
875 : 2321 : LWLockRelease(DSA_SCLASS_LOCK(area, DSA_SCLASS_SPAN_LARGE));
876 : : /* Free the span object so it can be reused. */
877 : 2321 : dsa_free(area, span_pointer);
878 : 2321 : return;
879 : : }
880 : :
881 : : #ifdef CLOBBER_FREED_MEMORY
882 : 72107 : memset(object, 0x7f, size);
883 : : #endif
884 : :
885 : 72107 : LWLockAcquire(DSA_SCLASS_LOCK(area, size_class), LW_EXCLUSIVE);
886 : :
887 : : /* Put the object on the span's freelist. */
888 [ - + ]: 72107 : Assert(object >= superblock);
889 [ - + ]: 72107 : Assert(object < superblock + DSA_SUPERBLOCK_SIZE);
890 [ - + ]: 72107 : Assert((object - superblock) % size == 0);
891 : 72107 : NextFreeObjectIndex(object) = span->firstfree;
892 : 72107 : span->firstfree = (object - superblock) / size;
893 : 72107 : ++span->nallocatable;
894 : :
895 : : /*
896 : : * See if the span needs to moved to a different fullness class, or be
897 : : * freed so its pages can be given back to the segment.
898 : : */
899 [ + + + - ]: 72107 : if (span->nallocatable == 1 && span->fclass == DSA_FULLNESS_CLASSES - 1)
900 : : {
901 : : /*
902 : : * The block was completely full and is located in the
903 : : * highest-numbered fullness class, which is never scanned for free
904 : : * chunks. We must move it to the next-lower fullness class.
905 : : */
906 : 91 : unlink_span(area, span);
907 : 91 : add_span_to_fullness_class(area, span, span_pointer,
908 : : DSA_FULLNESS_CLASSES - 2);
909 : :
910 : : /*
911 : : * If this is the only span, and there is no active span, then we
912 : : * should probably move this span to fullness class 1. (Otherwise if
913 : : * you allocate exactly all the objects in the only span, it moves to
914 : : * class 3, then you free them all, it moves to 2, and then is given
915 : : * back, leaving no active span).
916 : : */
917 : : }
918 [ + + ]: 72016 : else if (span->nallocatable == span->nmax &&
919 [ + + - + ]: 2654 : (span->fclass != 1 || span->prevspan != InvalidDsaPointer))
920 : : {
921 : : /*
922 : : * This entire block is free, and it's not the active block for this
923 : : * size class. Return the memory to the free page manager. We don't
924 : : * do this for the active block to prevent hysteresis: if we
925 : : * repeatedly allocate and free the only chunk in the active block, it
926 : : * will be very inefficient if we deallocate and reallocate the block
927 : : * every time.
928 : : */
2690 rhaas@postgresql.org 929 :GBC 8 : destroy_superblock(area, span_pointer);
930 : : }
931 : :
2690 rhaas@postgresql.org 932 :CBC 72107 : LWLockRelease(DSA_SCLASS_LOCK(area, size_class));
933 : : }
934 : :
935 : : /*
936 : : * Obtain a backend-local address for a dsa_pointer. 'dp' must point to
937 : : * memory allocated by the given area (possibly in another process) that
938 : : * hasn't yet been freed. This may cause a segment to be mapped into the
939 : : * current process if required, and may cause freed segments to be unmapped.
940 : : */
941 : : void *
942 : 10509525 : dsa_get_address(dsa_area *area, dsa_pointer dp)
943 : : {
944 : : dsa_segment_index index;
945 : : size_t offset;
946 : :
947 : : /* Convert InvalidDsaPointer to NULL. */
948 [ + + ]: 10509525 : if (!DsaPointerIsValid(dp))
949 : 1387281 : return NULL;
950 : :
951 : : /* Process any requests to detach from freed segments. */
952 : 9122244 : check_for_freed_segments(area);
953 : :
954 : : /* Break the dsa_pointer into its components. */
955 : 9122244 : index = DSA_EXTRACT_SEGMENT_NUMBER(dp);
956 : 9122244 : offset = DSA_EXTRACT_OFFSET(dp);
957 [ - + ]: 9122244 : Assert(index < DSA_MAX_SEGMENTS);
958 : :
959 : : /* Check if we need to cause this segment to be mapped in. */
960 [ + + ]: 9122244 : if (unlikely(area->segment_maps[index].mapped_address == NULL))
961 : : {
962 : : /* Call for effect (we don't need the result). */
963 : 16351 : get_segment_by_index(area, index);
964 : : }
965 : :
966 : 9122244 : return area->segment_maps[index].mapped_address + offset;
967 : : }
968 : :
969 : : /*
970 : : * Pin this area, so that it will continue to exist even if all backends
971 : : * detach from it. In that case, the area can still be reattached to if a
972 : : * handle has been recorded somewhere.
973 : : */
974 : : void
975 : 969 : dsa_pin(dsa_area *area)
976 : : {
977 : 969 : LWLockAcquire(DSA_AREA_LOCK(area), LW_EXCLUSIVE);
978 [ - + ]: 969 : if (area->control->pinned)
979 : : {
2690 rhaas@postgresql.org 980 :UBC 0 : LWLockRelease(DSA_AREA_LOCK(area));
981 [ # # ]: 0 : elog(ERROR, "dsa_area already pinned");
982 : : }
2690 rhaas@postgresql.org 983 :CBC 969 : area->control->pinned = true;
984 : 969 : ++area->control->refcnt;
985 : 969 : LWLockRelease(DSA_AREA_LOCK(area));
986 : 969 : }
987 : :
988 : : /*
989 : : * Undo the effects of dsa_pin, so that the given area can be freed when no
990 : : * backends are attached to it. May be called only if dsa_pin has been
991 : : * called.
992 : : */
993 : : void
2690 rhaas@postgresql.org 994 :UBC 0 : dsa_unpin(dsa_area *area)
995 : : {
996 : 0 : LWLockAcquire(DSA_AREA_LOCK(area), LW_EXCLUSIVE);
997 [ # # ]: 0 : Assert(area->control->refcnt > 1);
998 [ # # ]: 0 : if (!area->control->pinned)
999 : : {
1000 : 0 : LWLockRelease(DSA_AREA_LOCK(area));
1001 [ # # ]: 0 : elog(ERROR, "dsa_area not pinned");
1002 : : }
1003 : 0 : area->control->pinned = false;
1004 : 0 : --area->control->refcnt;
1005 : 0 : LWLockRelease(DSA_AREA_LOCK(area));
1006 : 0 : }
1007 : :
1008 : : /*
1009 : : * Set the total size limit for this area. This limit is checked whenever new
1010 : : * segments need to be allocated from the operating system. If the new size
1011 : : * limit is already exceeded, this has no immediate effect.
1012 : : *
1013 : : * Note that the total virtual memory usage may be temporarily larger than
1014 : : * this limit when segments have been freed, but not yet detached by all
1015 : : * backends that have attached to them.
1016 : : */
1017 : : void
2031 tmunro@postgresql.or 1018 :CBC 1796 : dsa_set_size_limit(dsa_area *area, size_t limit)
1019 : : {
2690 rhaas@postgresql.org 1020 : 1796 : LWLockAcquire(DSA_AREA_LOCK(area), LW_EXCLUSIVE);
1021 : 1796 : area->control->max_total_segment_size = limit;
1022 : 1796 : LWLockRelease(DSA_AREA_LOCK(area));
1023 : 1796 : }
1024 : :
1025 : : /* Return the total size of all active segments */
1026 : : size_t
38 john.naylor@postgres 1027 :GNC 378 : dsa_get_total_size(dsa_area *area)
1028 : : {
1029 : : size_t size;
1030 : :
1031 : 378 : LWLockAcquire(DSA_AREA_LOCK(area), LW_EXCLUSIVE);
1032 : 378 : size = area->control->total_segment_size;
1033 : 378 : LWLockRelease(DSA_AREA_LOCK(area));
1034 : :
1035 : 378 : return size;
1036 : : }
1037 : :
1038 : : /*
1039 : : * Aggressively free all spare memory in the hope of returning DSM segments to
1040 : : * the operating system.
1041 : : */
1042 : : void
2690 rhaas@postgresql.org 1043 :UBC 0 : dsa_trim(dsa_area *area)
1044 : : {
1045 : : int size_class;
1046 : :
1047 : : /*
1048 : : * Trim in reverse pool order so we get to the spans-of-spans last, just
1049 : : * in case any become entirely free while processing all the other pools.
1050 : : */
1051 [ # # ]: 0 : for (size_class = DSA_NUM_SIZE_CLASSES - 1; size_class >= 0; --size_class)
1052 : : {
1053 : 0 : dsa_area_pool *pool = &area->control->pools[size_class];
1054 : : dsa_pointer span_pointer;
1055 : :
1056 [ # # ]: 0 : if (size_class == DSA_SCLASS_SPAN_LARGE)
1057 : : {
1058 : : /* Large object frees give back segments aggressively already. */
1059 : 0 : continue;
1060 : : }
1061 : :
1062 : : /*
1063 : : * Search fullness class 1 only. That is where we expect to find an
1064 : : * entirely empty superblock (entirely empty superblocks in other
1065 : : * fullness classes are returned to the free page map by dsa_free).
1066 : : */
1067 : 0 : LWLockAcquire(DSA_SCLASS_LOCK(area, size_class), LW_EXCLUSIVE);
1068 : 0 : span_pointer = pool->spans[1];
1069 [ # # ]: 0 : while (DsaPointerIsValid(span_pointer))
1070 : : {
1071 : 0 : dsa_area_span *span = dsa_get_address(area, span_pointer);
1072 : 0 : dsa_pointer next = span->nextspan;
1073 : :
1074 [ # # ]: 0 : if (span->nallocatable == span->nmax)
1075 : 0 : destroy_superblock(area, span_pointer);
1076 : :
1077 : 0 : span_pointer = next;
1078 : : }
1079 : 0 : LWLockRelease(DSA_SCLASS_LOCK(area, size_class));
1080 : : }
1081 : 0 : }
1082 : :
1083 : : /*
1084 : : * Print out debugging information about the internal state of the shared
1085 : : * memory area.
1086 : : */
1087 : : void
1088 : 0 : dsa_dump(dsa_area *area)
1089 : : {
1090 : : size_t i,
1091 : : j;
1092 : :
1093 : : /*
1094 : : * Note: This gives an inconsistent snapshot as it acquires and releases
1095 : : * individual locks as it goes...
1096 : : */
1097 : :
1098 : 0 : LWLockAcquire(DSA_AREA_LOCK(area), LW_EXCLUSIVE);
2033 tmunro@postgresql.or 1099 : 0 : check_for_freed_segments_locked(area);
2690 rhaas@postgresql.org 1100 : 0 : fprintf(stderr, "dsa_area handle %x:\n", area->control->handle);
1101 : 0 : fprintf(stderr, " max_total_segment_size: %zu\n",
1102 : 0 : area->control->max_total_segment_size);
1103 : 0 : fprintf(stderr, " total_segment_size: %zu\n",
1104 : 0 : area->control->total_segment_size);
1105 : 0 : fprintf(stderr, " refcnt: %d\n", area->control->refcnt);
1106 [ # # ]: 0 : fprintf(stderr, " pinned: %c\n", area->control->pinned ? 't' : 'f');
1107 : 0 : fprintf(stderr, " segment bins:\n");
1108 [ # # ]: 0 : for (i = 0; i < DSA_NUM_SEGMENT_BINS; ++i)
1109 : : {
1110 [ # # ]: 0 : if (area->control->segment_bins[i] != DSA_SEGMENT_INDEX_NONE)
1111 : : {
1112 : : dsa_segment_index segment_index;
1113 : :
45 dgustafsson@postgres 1114 [ # # ]: 0 : if (i == 0)
1115 : 0 : fprintf(stderr,
1116 : : " segment bin %zu (no contiguous free pages):\n", i);
1117 : : else
1118 : 0 : fprintf(stderr,
1119 : : " segment bin %zu (at least %d contiguous pages free):\n",
1120 : 0 : i, 1 << (i - 1));
2690 rhaas@postgresql.org 1121 : 0 : segment_index = area->control->segment_bins[i];
1122 [ # # ]: 0 : while (segment_index != DSA_SEGMENT_INDEX_NONE)
1123 : : {
1124 : : dsa_segment_map *segment_map;
1125 : :
1126 : : segment_map =
1127 : 0 : get_segment_by_index(area, segment_index);
1128 : :
1129 : 0 : fprintf(stderr,
1130 : : " segment index %zu, usable_pages = %zu, "
1131 : : "contiguous_pages = %zu, mapped at %p\n",
1132 : : segment_index,
1133 : 0 : segment_map->header->usable_pages,
1134 : 0 : fpm_largest(segment_map->fpm),
1135 : : segment_map->mapped_address);
1136 : 0 : segment_index = segment_map->header->next;
1137 : : }
1138 : : }
1139 : : }
1140 : 0 : LWLockRelease(DSA_AREA_LOCK(area));
1141 : :
1142 : 0 : fprintf(stderr, " pools:\n");
1143 [ # # ]: 0 : for (i = 0; i < DSA_NUM_SIZE_CLASSES; ++i)
1144 : : {
1145 : 0 : bool found = false;
1146 : :
1147 : 0 : LWLockAcquire(DSA_SCLASS_LOCK(area, i), LW_EXCLUSIVE);
1148 [ # # ]: 0 : for (j = 0; j < DSA_FULLNESS_CLASSES; ++j)
1149 [ # # ]: 0 : if (DsaPointerIsValid(area->control->pools[i].spans[j]))
1150 : 0 : found = true;
1151 [ # # ]: 0 : if (found)
1152 : : {
1153 [ # # ]: 0 : if (i == DSA_SCLASS_BLOCK_OF_SPANS)
1154 : 0 : fprintf(stderr, " pool for blocks of span objects:\n");
1155 [ # # ]: 0 : else if (i == DSA_SCLASS_SPAN_LARGE)
1156 : 0 : fprintf(stderr, " pool for large object spans:\n");
1157 : : else
1158 : 0 : fprintf(stderr,
1159 : : " pool for size class %zu (object size %hu bytes):\n",
1160 : 0 : i, dsa_size_classes[i]);
1161 [ # # ]: 0 : for (j = 0; j < DSA_FULLNESS_CLASSES; ++j)
1162 : : {
1163 [ # # ]: 0 : if (!DsaPointerIsValid(area->control->pools[i].spans[j]))
1164 : 0 : fprintf(stderr, " fullness class %zu is empty\n", j);
1165 : : else
1166 : : {
1167 : 0 : dsa_pointer span_pointer = area->control->pools[i].spans[j];
1168 : :
1169 : 0 : fprintf(stderr, " fullness class %zu:\n", j);
1170 [ # # ]: 0 : while (DsaPointerIsValid(span_pointer))
1171 : : {
1172 : : dsa_area_span *span;
1173 : :
1174 : 0 : span = dsa_get_address(area, span_pointer);
1175 : 0 : fprintf(stderr,
1176 : : " span descriptor at "
1177 : : DSA_POINTER_FORMAT ", superblock at "
1178 : : DSA_POINTER_FORMAT
1179 : : ", pages = %zu, objects free = %hu/%hu\n",
1180 : : span_pointer, span->start, span->npages,
1181 : 0 : span->nallocatable, span->nmax);
1182 : 0 : span_pointer = span->nextspan;
1183 : : }
1184 : : }
1185 : : }
1186 : : }
1187 : 0 : LWLockRelease(DSA_SCLASS_LOCK(area, i));
1188 : : }
1189 : 0 : }
1190 : :
1191 : : /*
1192 : : * Return the smallest size that you can successfully provide to
1193 : : * dsa_create_in_place.
1194 : : */
1195 : : size_t
2690 rhaas@postgresql.org 1196 :CBC 6979 : dsa_minimum_size(void)
1197 : : {
1198 : : size_t size;
1199 : 6979 : int pages = 0;
1200 : :
1201 : 6979 : size = MAXALIGN(sizeof(dsa_area_control)) +
1202 : : MAXALIGN(sizeof(FreePageManager));
1203 : :
1204 : : /* Figure out how many pages we need, including the page map... */
1205 [ + + ]: 20937 : while (((size + FPM_PAGE_SIZE - 1) / FPM_PAGE_SIZE) > pages)
1206 : : {
1207 : 13958 : ++pages;
1208 : 13958 : size += sizeof(dsa_pointer);
1209 : : }
1210 : :
1211 : 6979 : return pages * FPM_PAGE_SIZE;
1212 : : }
1213 : :
1214 : : /*
1215 : : * Workhorse function for dsa_create and dsa_create_in_place.
1216 : : */
1217 : : static dsa_area *
1218 : 1376 : create_internal(void *place, size_t size,
1219 : : int tranche_id,
1220 : : dsm_handle control_handle,
1221 : : dsm_segment *control_segment,
1222 : : size_t init_segment_size, size_t max_segment_size)
1223 : : {
1224 : : dsa_area_control *control;
1225 : : dsa_area *area;
1226 : : dsa_segment_map *segment_map;
1227 : : size_t usable_pages;
1228 : : size_t total_pages;
1229 : : size_t metadata_bytes;
1230 : : int i;
1231 : :
1232 : : /* Check the initial and maximum block sizes */
18 msawada@postgresql.o 1233 [ - + ]:GNC 1376 : Assert(init_segment_size >= DSA_MIN_SEGMENT_SIZE);
1234 [ - + ]: 1376 : Assert(max_segment_size >= init_segment_size);
1235 [ - + ]: 1376 : Assert(max_segment_size <= DSA_MAX_SEGMENT_SIZE);
1236 : :
1237 : : /* Sanity check on the space we have to work in. */
2690 rhaas@postgresql.org 1238 [ - + ]:CBC 1376 : if (size < dsa_minimum_size())
2690 rhaas@postgresql.org 1239 [ # # ]:UBC 0 : elog(ERROR, "dsa_area space must be at least %zu, but %zu provided",
1240 : : dsa_minimum_size(), size);
1241 : :
1242 : : /* Now figure out how much space is usable */
2690 rhaas@postgresql.org 1243 :CBC 1376 : total_pages = size / FPM_PAGE_SIZE;
1244 : 1376 : metadata_bytes =
1245 : : MAXALIGN(sizeof(dsa_area_control)) +
1246 : 1376 : MAXALIGN(sizeof(FreePageManager)) +
1247 : : total_pages * sizeof(dsa_pointer);
1248 : : /* Add padding up to next page boundary. */
1249 [ + - ]: 1376 : if (metadata_bytes % FPM_PAGE_SIZE != 0)
1250 : 1376 : metadata_bytes += FPM_PAGE_SIZE - (metadata_bytes % FPM_PAGE_SIZE);
1251 [ - + ]: 1376 : Assert(metadata_bytes <= size);
1252 : 1376 : usable_pages = (size - metadata_bytes) / FPM_PAGE_SIZE;
1253 : :
1254 : : /*
1255 : : * Initialize the dsa_area_control object located at the start of the
1256 : : * space.
1257 : : */
1258 : 1376 : control = (dsa_area_control *) place;
1353 tmunro@postgresql.or 1259 : 1376 : memset(place, 0, sizeof(*control));
2690 rhaas@postgresql.org 1260 : 1376 : control->segment_header.magic =
1261 : 1376 : DSA_SEGMENT_HEADER_MAGIC ^ control_handle ^ 0;
1262 : 1376 : control->segment_header.next = DSA_SEGMENT_INDEX_NONE;
1263 : 1376 : control->segment_header.prev = DSA_SEGMENT_INDEX_NONE;
1264 : 1376 : control->segment_header.usable_pages = usable_pages;
1265 : 1376 : control->segment_header.freed = false;
18 msawada@postgresql.o 1266 :GNC 1376 : control->segment_header.size = size;
2690 rhaas@postgresql.org 1267 :CBC 1376 : control->handle = control_handle;
18 msawada@postgresql.o 1268 :GNC 1376 : control->init_segment_size = init_segment_size;
1269 : 1376 : control->max_segment_size = max_segment_size;
2031 tmunro@postgresql.or 1270 :CBC 1376 : control->max_total_segment_size = (size_t) -1;
2690 rhaas@postgresql.org 1271 : 1376 : control->total_segment_size = size;
1272 : 1376 : control->segment_handles[0] = control_handle;
1273 [ + + ]: 23392 : for (i = 0; i < DSA_NUM_SEGMENT_BINS; ++i)
1274 : 22016 : control->segment_bins[i] = DSA_SEGMENT_INDEX_NONE;
1275 : 1376 : control->refcnt = 1;
1276 : 1376 : control->lwlock_tranche_id = tranche_id;
1277 : :
1278 : : /*
1279 : : * Create the dsa_area object that this backend will use to access the
1280 : : * area. Other backends will need to obtain their own dsa_area object by
1281 : : * attaching.
1282 : : */
1283 : 1376 : area = palloc(sizeof(dsa_area));
1284 : 1376 : area->control = control;
151 heikki.linnakangas@i 1285 :GNC 1376 : area->resowner = CurrentResourceOwner;
2690 rhaas@postgresql.org 1286 :CBC 1376 : memset(area->segment_maps, 0, sizeof(dsa_segment_map) * DSA_MAX_SEGMENTS);
1287 : 1376 : area->high_segment_index = 0;
2561 andres@anarazel.de 1288 : 1376 : area->freed_segment_counter = 0;
2690 rhaas@postgresql.org 1289 : 1376 : LWLockInitialize(&control->lock, control->lwlock_tranche_id);
1290 [ + + ]: 53664 : for (i = 0; i < DSA_NUM_SIZE_CLASSES; ++i)
1291 : 52288 : LWLockInitialize(DSA_SCLASS_LOCK(area, i),
1292 : : control->lwlock_tranche_id);
1293 : :
1294 : : /* Set up the segment map for this process's mapping. */
1295 : 1376 : segment_map = &area->segment_maps[0];
1296 : 1376 : segment_map->segment = control_segment;
1297 : 1376 : segment_map->mapped_address = place;
1298 : 1376 : segment_map->header = (dsa_segment_header *) place;
1299 : 1376 : segment_map->fpm = (FreePageManager *)
1300 : 1376 : (segment_map->mapped_address +
1301 : : MAXALIGN(sizeof(dsa_area_control)));
1302 : 1376 : segment_map->pagemap = (dsa_pointer *)
1303 : 1376 : (segment_map->mapped_address +
1304 : 1376 : MAXALIGN(sizeof(dsa_area_control)) +
1305 : : MAXALIGN(sizeof(FreePageManager)));
1306 : :
1307 : : /* Set up the free page map. */
1308 : 1376 : FreePageManagerInitialize(segment_map->fpm, segment_map->mapped_address);
1309 : : /* There can be 0 usable pages if size is dsa_minimum_size(). */
1310 : :
1311 [ + + ]: 1376 : if (usable_pages > 0)
1312 : 1044 : FreePageManagerPut(segment_map->fpm, metadata_bytes / FPM_PAGE_SIZE,
1313 : : usable_pages);
1314 : :
1315 : : /* Put this segment into the appropriate bin. */
1316 : 1376 : control->segment_bins[contiguous_pages_to_segment_bin(usable_pages)] = 0;
1317 : 1376 : segment_map->header->bin = contiguous_pages_to_segment_bin(usable_pages);
1318 : :
1319 : 1376 : return area;
1320 : : }
1321 : :
1322 : : /*
1323 : : * Workhorse function for dsa_attach and dsa_attach_in_place.
1324 : : */
1325 : : static dsa_area *
1326 : 22382 : attach_internal(void *place, dsm_segment *segment, dsa_handle handle)
1327 : : {
1328 : : dsa_area_control *control;
1329 : : dsa_area *area;
1330 : : dsa_segment_map *segment_map;
1331 : :
1332 : 22382 : control = (dsa_area_control *) place;
1333 [ - + ]: 22382 : Assert(control->handle == handle);
1334 [ - + ]: 22382 : Assert(control->segment_handles[0] == handle);
1335 [ - + ]: 22382 : Assert(control->segment_header.magic ==
1336 : : (DSA_SEGMENT_HEADER_MAGIC ^ handle ^ 0));
1337 : :
1338 : : /* Build the backend-local area object. */
1339 : 22382 : area = palloc(sizeof(dsa_area));
1340 : 22382 : area->control = control;
151 heikki.linnakangas@i 1341 :GNC 22382 : area->resowner = CurrentResourceOwner;
2690 rhaas@postgresql.org 1342 :CBC 22382 : memset(&area->segment_maps[0], 0,
1343 : : sizeof(dsa_segment_map) * DSA_MAX_SEGMENTS);
1344 : 22382 : area->high_segment_index = 0;
1345 : :
1346 : : /* Set up the segment map for this process's mapping. */
1347 : 22382 : segment_map = &area->segment_maps[0];
2489 tgl@sss.pgh.pa.us 1348 : 22382 : segment_map->segment = segment; /* NULL for in-place */
2690 rhaas@postgresql.org 1349 : 22382 : segment_map->mapped_address = place;
1350 : 22382 : segment_map->header = (dsa_segment_header *) segment_map->mapped_address;
1351 : 22382 : segment_map->fpm = (FreePageManager *)
1352 : 22382 : (segment_map->mapped_address + MAXALIGN(sizeof(dsa_area_control)));
1353 : 22382 : segment_map->pagemap = (dsa_pointer *)
1354 : 22382 : (segment_map->mapped_address + MAXALIGN(sizeof(dsa_area_control)) +
1355 : : MAXALIGN(sizeof(FreePageManager)));
1356 : :
1357 : : /* Bump the reference count. */
1358 : 22382 : LWLockAcquire(DSA_AREA_LOCK(area), LW_EXCLUSIVE);
2573 1359 [ - + ]: 22382 : if (control->refcnt == 0)
1360 : : {
1361 : : /* We can't attach to a DSA area that has already been destroyed. */
2573 rhaas@postgresql.org 1362 [ # # ]:UBC 0 : ereport(ERROR,
1363 : : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
1364 : : errmsg("could not attach to dynamic shared area")));
1365 : : }
2690 rhaas@postgresql.org 1366 :CBC 22382 : ++control->refcnt;
2561 andres@anarazel.de 1367 : 22382 : area->freed_segment_counter = area->control->freed_segment_counter;
2690 rhaas@postgresql.org 1368 : 22382 : LWLockRelease(DSA_AREA_LOCK(area));
1369 : :
1370 : 22382 : return area;
1371 : : }
1372 : :
1373 : : /*
1374 : : * Add a new span to fullness class 1 of the indicated pool.
1375 : : */
1376 : : static void
1377 : 11078 : init_span(dsa_area *area,
1378 : : dsa_pointer span_pointer,
1379 : : dsa_area_pool *pool, dsa_pointer start, size_t npages,
1380 : : uint16 size_class)
1381 : : {
1382 : 11078 : dsa_area_span *span = dsa_get_address(area, span_pointer);
2031 tmunro@postgresql.or 1383 : 11078 : size_t obsize = dsa_size_classes[size_class];
1384 : :
1385 : : /*
1386 : : * The per-pool lock must be held because we manipulate the span list for
1387 : : * this pool.
1388 : : */
2690 rhaas@postgresql.org 1389 [ - + ]: 11078 : Assert(LWLockHeldByMe(DSA_SCLASS_LOCK(area, size_class)));
1390 : :
1391 : : /* Push this span onto the front of the span list for fullness class 1. */
1392 [ + + ]: 11078 : if (DsaPointerIsValid(pool->spans[1]))
1393 : : {
1394 : : dsa_area_span *head = (dsa_area_span *)
331 tgl@sss.pgh.pa.us 1395 : 2197 : dsa_get_address(area, pool->spans[1]);
1396 : :
2690 rhaas@postgresql.org 1397 : 2197 : head->prevspan = span_pointer;
1398 : : }
1399 : 11078 : span->pool = DsaAreaPoolToDsaPointer(area, pool);
1400 : 11078 : span->nextspan = pool->spans[1];
1401 : 11078 : span->prevspan = InvalidDsaPointer;
1402 : 11078 : pool->spans[1] = span_pointer;
1403 : :
1404 : 11078 : span->start = start;
1405 : 11078 : span->npages = npages;
1406 : 11078 : span->size_class = size_class;
1407 : 11078 : span->ninitialized = 0;
1408 [ + + ]: 11078 : if (size_class == DSA_SCLASS_BLOCK_OF_SPANS)
1409 : : {
1410 : : /*
1411 : : * A block-of-spans contains its own descriptor, so mark one object as
1412 : : * initialized and reduce the count of allocatable objects by one.
1413 : : * Doing this here has the side effect of also reducing nmax by one,
1414 : : * which is important to make sure we free this object at the correct
1415 : : * time.
1416 : : */
1417 : 1127 : span->ninitialized = 1;
1418 : 1127 : span->nallocatable = FPM_PAGE_SIZE / obsize - 1;
1419 : : }
1420 [ + + ]: 9951 : else if (size_class != DSA_SCLASS_SPAN_LARGE)
1421 : 7537 : span->nallocatable = DSA_SUPERBLOCK_SIZE / obsize;
1422 : 11078 : span->firstfree = DSA_SPAN_NOTHING_FREE;
1423 : 11078 : span->nmax = span->nallocatable;
1424 : 11078 : span->fclass = 1;
1425 : 11078 : }
1426 : :
1427 : : /*
1428 : : * Transfer the first span in one fullness class to the head of another
1429 : : * fullness class.
1430 : : */
1431 : : static bool
1432 : 18092 : transfer_first_span(dsa_area *area,
1433 : : dsa_area_pool *pool, int fromclass, int toclass)
1434 : : {
1435 : : dsa_pointer span_pointer;
1436 : : dsa_area_span *span;
1437 : : dsa_area_span *nextspan;
1438 : :
1439 : : /* Can't do it if source list is empty. */
1440 : 18092 : span_pointer = pool->spans[fromclass];
1441 [ + + ]: 18092 : if (!DsaPointerIsValid(span_pointer))
1442 : 17329 : return false;
1443 : :
1444 : : /* Remove span from head of source list. */
1445 : 763 : span = dsa_get_address(area, span_pointer);
1446 : 763 : pool->spans[fromclass] = span->nextspan;
1447 [ + + ]: 763 : if (DsaPointerIsValid(span->nextspan))
1448 : : {
1449 : : nextspan = (dsa_area_span *)
1450 : 30 : dsa_get_address(area, span->nextspan);
1451 : 30 : nextspan->prevspan = InvalidDsaPointer;
1452 : : }
1453 : :
1454 : : /* Add span to head of target list. */
1455 : 763 : span->nextspan = pool->spans[toclass];
1456 : 763 : pool->spans[toclass] = span_pointer;
1457 [ + + ]: 763 : if (DsaPointerIsValid(span->nextspan))
1458 : : {
1459 : : nextspan = (dsa_area_span *)
1460 : 279 : dsa_get_address(area, span->nextspan);
1461 : 279 : nextspan->prevspan = span_pointer;
1462 : : }
1463 : 763 : span->fclass = toclass;
1464 : :
1465 : 763 : return true;
1466 : : }
1467 : :
1468 : : /*
1469 : : * Allocate one object of the requested size class from the given area.
1470 : : */
1471 : : static inline dsa_pointer
1472 : 512944 : alloc_object(dsa_area *area, int size_class)
1473 : : {
1474 : 512944 : dsa_area_pool *pool = &area->control->pools[size_class];
1475 : : dsa_area_span *span;
1476 : : dsa_pointer block;
1477 : : dsa_pointer result;
1478 : : char *object;
1479 : : size_t size;
1480 : :
1481 : : /*
1482 : : * Even though ensure_active_superblock can in turn call alloc_object if
1483 : : * it needs to allocate a new span, that's always from a different pool,
1484 : : * and the order of lock acquisition is always the same, so it's OK that
1485 : : * we hold this lock for the duration of this function.
1486 : : */
1487 [ - + ]: 512944 : Assert(!LWLockHeldByMe(DSA_SCLASS_LOCK(area, size_class)));
1488 : 512944 : LWLockAcquire(DSA_SCLASS_LOCK(area, size_class), LW_EXCLUSIVE);
1489 : :
1490 : : /*
1491 : : * If there's no active superblock, we must successfully obtain one or
1492 : : * fail the request.
1493 : : */
1494 [ + + ]: 512944 : if (!DsaPointerIsValid(pool->spans[1]) &&
1495 [ - + ]: 8727 : !ensure_active_superblock(area, pool, size_class))
1496 : : {
2690 rhaas@postgresql.org 1497 :UBC 0 : result = InvalidDsaPointer;
1498 : : }
1499 : : else
1500 : : {
1501 : : /*
1502 : : * There should be a block in fullness class 1 at this point, and it
1503 : : * should never be completely full. Thus we can either pop an object
1504 : : * from the free list or, failing that, initialize a new object.
1505 : : */
2690 rhaas@postgresql.org 1506 [ - + ]:CBC 512944 : Assert(DsaPointerIsValid(pool->spans[1]));
1507 : : span = (dsa_area_span *)
1508 : 512944 : dsa_get_address(area, pool->spans[1]);
1509 [ - + ]: 512944 : Assert(span->nallocatable > 0);
1510 : 512944 : block = span->start;
1511 [ - + ]: 512944 : Assert(size_class < DSA_NUM_SIZE_CLASSES);
1512 : 512944 : size = dsa_size_classes[size_class];
1513 [ + + ]: 512944 : if (span->firstfree != DSA_SPAN_NOTHING_FREE)
1514 : : {
1515 : 64544 : result = block + span->firstfree * size;
1516 : 64544 : object = dsa_get_address(area, result);
1517 : 64544 : span->firstfree = NextFreeObjectIndex(object);
1518 : : }
1519 : : else
1520 : : {
1521 : 448400 : result = block + span->ninitialized * size;
1522 : 448400 : ++span->ninitialized;
1523 : : }
1524 : 512944 : --span->nallocatable;
1525 : :
1526 : : /* If it's now full, move it to the highest-numbered fullness class. */
1527 [ + + ]: 512944 : if (span->nallocatable == 0)
1528 : 702 : transfer_first_span(area, pool, 1, DSA_FULLNESS_CLASSES - 1);
1529 : : }
1530 : :
1531 [ - + ]: 512944 : Assert(LWLockHeldByMe(DSA_SCLASS_LOCK(area, size_class)));
1532 : 512944 : LWLockRelease(DSA_SCLASS_LOCK(area, size_class));
1533 : :
1534 : 512944 : return result;
1535 : : }
1536 : :
1537 : : /*
1538 : : * Ensure an active (i.e. fullness class 1) superblock, unless all existing
1539 : : * superblocks are completely full and no more can be allocated.
1540 : : *
1541 : : * Fullness classes K of 0..N are loosely intended to represent blocks whose
1542 : : * utilization percentage is at least K/N, but we only enforce this rigorously
1543 : : * for the highest-numbered fullness class, which always contains exactly
1544 : : * those blocks that are completely full. It's otherwise acceptable for a
1545 : : * block to be in a higher-numbered fullness class than the one to which it
1546 : : * logically belongs. In addition, the active block, which is always the
1547 : : * first block in fullness class 1, is permitted to have a higher allocation
1548 : : * percentage than would normally be allowable for that fullness class; we
1549 : : * don't move it until it's completely full, and then it goes to the
1550 : : * highest-numbered fullness class.
1551 : : *
1552 : : * It might seem odd that the active block is the head of fullness class 1
1553 : : * rather than fullness class 0, but experience with other allocators has
1554 : : * shown that it's usually better to allocate from a block that's moderately
1555 : : * full rather than one that's nearly empty. Insofar as is reasonably
1556 : : * possible, we want to avoid performing new allocations in a block that would
1557 : : * otherwise become empty soon.
1558 : : */
1559 : : static bool
1560 : 8727 : ensure_active_superblock(dsa_area *area, dsa_area_pool *pool,
1561 : : int size_class)
1562 : : {
1563 : : dsa_pointer span_pointer;
1564 : : dsa_pointer start_pointer;
2031 tmunro@postgresql.or 1565 : 8727 : size_t obsize = dsa_size_classes[size_class];
1566 : : size_t nmax;
1567 : : int fclass;
1568 : 8727 : size_t npages = 1;
1569 : : size_t first_page;
1570 : : size_t i;
1571 : : dsa_segment_map *segment_map;
1572 : :
2690 rhaas@postgresql.org 1573 [ - + ]: 8727 : Assert(LWLockHeldByMe(DSA_SCLASS_LOCK(area, size_class)));
1574 : :
1575 : : /*
1576 : : * Compute the number of objects that will fit in a block of this size
1577 : : * class. Span-of-spans blocks are just a single page, and the first
1578 : : * object isn't available for use because it describes the block-of-spans
1579 : : * itself.
1580 : : */
1581 [ + + ]: 8727 : if (size_class == DSA_SCLASS_BLOCK_OF_SPANS)
1582 : 1127 : nmax = FPM_PAGE_SIZE / obsize - 1;
1583 : : else
1584 : 7600 : nmax = DSA_SUPERBLOCK_SIZE / obsize;
1585 : :
1586 : : /*
1587 : : * If fullness class 1 is empty, try to find a span to put in it by
1588 : : * scanning higher-numbered fullness classes (excluding the last one,
1589 : : * whose blocks are certain to all be completely full).
1590 : : */
1591 [ + + ]: 17452 : for (fclass = 2; fclass < DSA_FULLNESS_CLASSES - 1; ++fclass)
1592 : : {
1593 : 8727 : span_pointer = pool->spans[fclass];
1594 : :
1595 [ + + ]: 8826 : while (DsaPointerIsValid(span_pointer))
1596 : : {
1597 : : int tfclass;
1598 : : dsa_area_span *span;
1599 : : dsa_area_span *nextspan;
1600 : : dsa_area_span *prevspan;
1601 : : dsa_pointer next_span_pointer;
1602 : :
1603 : : span = (dsa_area_span *)
1604 : 99 : dsa_get_address(area, span_pointer);
1605 : 99 : next_span_pointer = span->nextspan;
1606 : :
1607 : : /* Figure out what fullness class should contain this span. */
1608 : 99 : tfclass = (nmax - span->nallocatable)
1609 : 99 : * (DSA_FULLNESS_CLASSES - 1) / nmax;
1610 : :
1611 : : /* Look up next span. */
1612 [ + + ]: 99 : if (DsaPointerIsValid(span->nextspan))
1613 : : nextspan = (dsa_area_span *)
1614 : 36 : dsa_get_address(area, span->nextspan);
1615 : : else
1616 : 63 : nextspan = NULL;
1617 : :
1618 : : /*
1619 : : * If utilization has dropped enough that this now belongs in some
1620 : : * other fullness class, move it there.
1621 : : */
1622 [ + + ]: 99 : if (tfclass < fclass)
1623 : : {
1624 : : /* Remove from the current fullness class list. */
1625 [ + - ]: 3 : if (pool->spans[fclass] == span_pointer)
1626 : : {
1627 : : /* It was the head; remove it. */
1628 [ - + ]: 3 : Assert(!DsaPointerIsValid(span->prevspan));
1629 : 3 : pool->spans[fclass] = span->nextspan;
1630 [ + + ]: 3 : if (nextspan != NULL)
2690 rhaas@postgresql.org 1631 :GBC 2 : nextspan->prevspan = InvalidDsaPointer;
1632 : : }
1633 : : else
1634 : : {
1635 : : /* It was not the head. */
2690 rhaas@postgresql.org 1636 [ # # ]:UBC 0 : Assert(DsaPointerIsValid(span->prevspan));
1637 : : prevspan = (dsa_area_span *)
1638 : 0 : dsa_get_address(area, span->prevspan);
1639 : 0 : prevspan->nextspan = span->nextspan;
1640 : : }
2690 rhaas@postgresql.org 1641 [ + + ]:CBC 3 : if (nextspan != NULL)
2690 rhaas@postgresql.org 1642 :GBC 2 : nextspan->prevspan = span->prevspan;
1643 : :
1644 : : /* Push onto the head of the new fullness class list. */
2690 rhaas@postgresql.org 1645 :CBC 3 : span->nextspan = pool->spans[tfclass];
1646 : 3 : pool->spans[tfclass] = span_pointer;
1647 : 3 : span->prevspan = InvalidDsaPointer;
1648 [ - + ]: 3 : if (DsaPointerIsValid(span->nextspan))
1649 : : {
1650 : : nextspan = (dsa_area_span *)
2690 rhaas@postgresql.org 1651 :UBC 0 : dsa_get_address(area, span->nextspan);
1652 : 0 : nextspan->prevspan = span_pointer;
1653 : : }
2690 rhaas@postgresql.org 1654 :CBC 3 : span->fclass = tfclass;
1655 : : }
1656 : :
1657 : : /* Advance to next span on list. */
1658 : 99 : span_pointer = next_span_pointer;
1659 : : }
1660 : :
1661 : : /* Stop now if we found a suitable block. */
1662 [ + + ]: 8727 : if (DsaPointerIsValid(pool->spans[1]))
2690 rhaas@postgresql.org 1663 :GBC 2 : return true;
1664 : : }
1665 : :
1666 : : /*
1667 : : * If there are no blocks that properly belong in fullness class 1, pick
1668 : : * one from some other fullness class and move it there anyway, so that we
1669 : : * have an allocation target. Our last choice is to transfer a block
1670 : : * that's almost empty (and might become completely empty soon if left
1671 : : * alone), but even that is better than failing, which is what we must do
1672 : : * if there are no blocks at all with freespace.
1673 : : */
2690 rhaas@postgresql.org 1674 [ - + ]:CBC 8725 : Assert(!DsaPointerIsValid(pool->spans[1]));
1675 [ + + ]: 17390 : for (fclass = 2; fclass < DSA_FULLNESS_CLASSES - 1; ++fclass)
1676 [ + + ]: 8725 : if (transfer_first_span(area, pool, fclass, 1))
1677 : 60 : return true;
1678 [ + - + + ]: 17330 : if (!DsaPointerIsValid(pool->spans[1]) &&
1679 : 8665 : transfer_first_span(area, pool, 0, 1))
1680 : 1 : return true;
1681 : :
1682 : : /*
1683 : : * We failed to find an existing span with free objects, so we need to
1684 : : * allocate a new superblock and construct a new span to manage it.
1685 : : *
1686 : : * First, get a dsa_area_span object to describe the new superblock block
1687 : : * ... unless this allocation is for a dsa_area_span object, in which case
1688 : : * that's surely not going to work. We handle that case by storing the
1689 : : * span describing a block-of-spans inline.
1690 : : */
1691 [ + + ]: 8664 : if (size_class != DSA_SCLASS_BLOCK_OF_SPANS)
1692 : : {
1693 : 7537 : span_pointer = alloc_object(area, DSA_SCLASS_BLOCK_OF_SPANS);
1694 [ - + ]: 7537 : if (!DsaPointerIsValid(span_pointer))
2690 rhaas@postgresql.org 1695 :UBC 0 : return false;
2690 rhaas@postgresql.org 1696 :CBC 7537 : npages = DSA_PAGES_PER_SUPERBLOCK;
1697 : : }
1698 : :
1699 : : /* Find or create a segment and allocate the superblock. */
1700 : 8664 : LWLockAcquire(DSA_AREA_LOCK(area), LW_EXCLUSIVE);
1701 : 8664 : segment_map = get_best_segment(area, npages);
1702 [ + + ]: 8664 : if (segment_map == NULL)
1703 : : {
1704 : 898 : segment_map = make_new_segment(area, npages);
1705 [ - + ]: 898 : if (segment_map == NULL)
1706 : : {
2690 rhaas@postgresql.org 1707 :UBC 0 : LWLockRelease(DSA_AREA_LOCK(area));
1708 : 0 : return false;
1709 : : }
1710 : : }
1711 : :
1712 : : /*
1713 : : * This shouldn't happen: get_best_segment() or make_new_segment()
1714 : : * promised that we can successfully allocate npages.
1715 : : */
2690 rhaas@postgresql.org 1716 [ - + ]:CBC 8664 : if (!FreePageManagerGet(segment_map->fpm, npages, &first_page))
1875 tmunro@postgresql.or 1717 [ # # ]:UBC 0 : elog(FATAL,
1718 : : "dsa_allocate could not find %zu free pages for superblock",
1719 : : npages);
2690 rhaas@postgresql.org 1720 :CBC 8664 : LWLockRelease(DSA_AREA_LOCK(area));
1721 : :
1722 : : /* Compute the start of the superblock. */
1723 : 8664 : start_pointer =
1724 : 8664 : DSA_MAKE_POINTER(get_segment_index(area, segment_map),
1725 : : first_page * FPM_PAGE_SIZE);
1726 : :
1727 : : /*
1728 : : * If this is a block-of-spans, carve the descriptor right out of the
1729 : : * allocated space.
1730 : : */
1731 [ + + ]: 8664 : if (size_class == DSA_SCLASS_BLOCK_OF_SPANS)
1732 : : {
1733 : : /*
1734 : : * We have a pointer into the segment. We need to build a dsa_pointer
1735 : : * from the segment index and offset into the segment.
1736 : : */
1737 : 1127 : span_pointer = start_pointer;
1738 : : }
1739 : :
1740 : : /* Initialize span and pagemap. */
1741 : 8664 : init_span(area, span_pointer, pool, start_pointer, npages, size_class);
1742 [ + + ]: 130383 : for (i = 0; i < npages; ++i)
1743 : 121719 : segment_map->pagemap[first_page + i] = span_pointer;
1744 : :
1745 : 8664 : return true;
1746 : : }
1747 : :
1748 : : /*
1749 : : * Return the segment map corresponding to a given segment index, mapping the
1750 : : * segment in if necessary. For internal segment book-keeping, this is called
1751 : : * with the area lock held. It is also called by dsa_free and dsa_get_address
1752 : : * without any locking, relying on the fact they have a known live segment
1753 : : * index and they always call check_for_freed_segments to ensures that any
1754 : : * freed segment occupying the same slot is detached first.
1755 : : */
1756 : : static dsa_segment_map *
1757 : 101790 : get_segment_by_index(dsa_area *area, dsa_segment_index index)
1758 : : {
1759 [ + + ]: 101790 : if (unlikely(area->segment_maps[index].mapped_address == NULL))
1760 : : {
1761 : : dsm_handle handle;
1762 : : dsm_segment *segment;
1763 : : dsa_segment_map *segment_map;
1764 : : ResourceOwner oldowner;
1765 : :
1766 : : /*
1767 : : * If we are reached by dsa_free or dsa_get_address, there must be at
1768 : : * least one object allocated in the referenced segment. Otherwise,
1769 : : * their caller has a double-free or access-after-free bug, which we
1770 : : * have no hope of detecting. So we know it's safe to access this
1771 : : * array slot without holding a lock; it won't change underneath us.
1772 : : * Furthermore, we know that we can see the latest contents of the
1773 : : * slot, as explained in check_for_freed_segments, which those
1774 : : * functions call before arriving here.
1775 : : */
1776 : 16381 : handle = area->control->segment_handles[index];
1777 : :
1778 : : /* It's an error to try to access an unused slot. */
1779 [ - + ]: 16381 : if (handle == DSM_HANDLE_INVALID)
2690 rhaas@postgresql.org 1780 [ # # ]:UBC 0 : elog(ERROR,
1781 : : "dsa_area could not attach to a segment that has been freed");
1782 : :
151 heikki.linnakangas@i 1783 :GNC 16381 : oldowner = CurrentResourceOwner;
1784 : 16381 : CurrentResourceOwner = area->resowner;
2690 rhaas@postgresql.org 1785 :CBC 16381 : segment = dsm_attach(handle);
151 heikki.linnakangas@i 1786 :GNC 16381 : CurrentResourceOwner = oldowner;
2690 rhaas@postgresql.org 1787 [ - + ]:CBC 16381 : if (segment == NULL)
2690 rhaas@postgresql.org 1788 [ # # ]:UBC 0 : elog(ERROR, "dsa_area could not attach to segment");
2690 rhaas@postgresql.org 1789 :CBC 16381 : segment_map = &area->segment_maps[index];
1790 : 16381 : segment_map->segment = segment;
1791 : 16381 : segment_map->mapped_address = dsm_segment_address(segment);
1792 : 16381 : segment_map->header =
1793 : 16381 : (dsa_segment_header *) segment_map->mapped_address;
1794 : 16381 : segment_map->fpm = (FreePageManager *)
1795 : 16381 : (segment_map->mapped_address +
1796 : : MAXALIGN(sizeof(dsa_segment_header)));
1797 : 16381 : segment_map->pagemap = (dsa_pointer *)
1798 : 16381 : (segment_map->mapped_address +
1799 : 16381 : MAXALIGN(sizeof(dsa_segment_header)) +
1800 : : MAXALIGN(sizeof(FreePageManager)));
1801 : :
1802 : : /* Remember the highest index this backend has ever mapped. */
1803 [ + - ]: 16381 : if (area->high_segment_index < index)
1804 : 16381 : area->high_segment_index = index;
1805 : :
1806 [ - + ]: 16381 : Assert(segment_map->header->magic ==
1807 : : (DSA_SEGMENT_HEADER_MAGIC ^ area->control->handle ^ index));
1808 : : }
1809 : :
1810 : : /*
1811 : : * Callers of dsa_get_address() and dsa_free() don't hold the area lock,
1812 : : * but it's a bug in the calling code and undefined behavior if the
1813 : : * address is not live (ie if the segment might possibly have been freed,
1814 : : * they're trying to use a dangling pointer).
1815 : : *
1816 : : * For dsa.c code that holds the area lock to manipulate segment_bins
1817 : : * lists, it would be a bug if we ever reach a freed segment here. After
1818 : : * it's marked as freed, the only thing any backend should do with it is
1819 : : * unmap it, and it should always have done that in
1820 : : * check_for_freed_segments_locked() before arriving here to resolve an
1821 : : * index to a segment_map.
1822 : : *
1823 : : * Either way we can assert that we aren't returning a freed segment.
1824 : : */
2033 tmunro@postgresql.or 1825 [ - + ]: 101790 : Assert(!area->segment_maps[index].header->freed);
1826 : :
2690 rhaas@postgresql.org 1827 : 101790 : return &area->segment_maps[index];
1828 : : }
1829 : :
1830 : : /*
1831 : : * Return a superblock to the free page manager. If the underlying segment
1832 : : * has become entirely free, then return it to the operating system.
1833 : : *
1834 : : * The appropriate pool lock must be held.
1835 : : */
1836 : : static void
2690 rhaas@postgresql.org 1837 :GBC 8 : destroy_superblock(dsa_area *area, dsa_pointer span_pointer)
1838 : : {
1839 : 8 : dsa_area_span *span = dsa_get_address(area, span_pointer);
1840 : 8 : int size_class = span->size_class;
1841 : : dsa_segment_map *segment_map;
1842 : :
1843 : :
1844 : : /* Remove it from its fullness class list. */
1845 : 8 : unlink_span(area, span);
1846 : :
1847 : : /*
1848 : : * Note: Here we acquire the area lock while we already hold a per-pool
1849 : : * lock. We never hold the area lock and then take a pool lock, or we
1850 : : * could deadlock.
1851 : : */
1852 : 8 : LWLockAcquire(DSA_AREA_LOCK(area), LW_EXCLUSIVE);
2033 tmunro@postgresql.or 1853 : 8 : check_for_freed_segments_locked(area);
1854 : : segment_map =
1855 : 8 : get_segment_by_index(area, DSA_EXTRACT_SEGMENT_NUMBER(span->start));
2690 rhaas@postgresql.org 1856 : 8 : FreePageManagerPut(segment_map->fpm,
1857 : 8 : DSA_EXTRACT_OFFSET(span->start) / FPM_PAGE_SIZE,
1858 : : span->npages);
1859 : : /* Check if the segment is now entirely free. */
1860 [ - + ]: 8 : if (fpm_largest(segment_map->fpm) == segment_map->header->usable_pages)
1861 : : {
2690 rhaas@postgresql.org 1862 :UBC 0 : dsa_segment_index index = get_segment_index(area, segment_map);
1863 : :
1864 : : /* If it's not the segment with extra control data, free it. */
1865 [ # # ]: 0 : if (index != 0)
1866 : : {
1867 : : /*
1868 : : * Give it back to the OS, and allow other backends to detect that
1869 : : * they need to detach.
1870 : : */
1871 : 0 : unlink_segment(area, segment_map);
1872 : 0 : segment_map->header->freed = true;
1873 [ # # ]: 0 : Assert(area->control->total_segment_size >=
1874 : : segment_map->header->size);
1875 : 0 : area->control->total_segment_size -=
1876 : 0 : segment_map->header->size;
1877 : 0 : dsm_unpin_segment(dsm_segment_handle(segment_map->segment));
1878 : 0 : dsm_detach(segment_map->segment);
1879 : 0 : area->control->segment_handles[index] = DSM_HANDLE_INVALID;
1880 : 0 : ++area->control->freed_segment_counter;
1881 : 0 : segment_map->segment = NULL;
1882 : 0 : segment_map->header = NULL;
1883 : 0 : segment_map->mapped_address = NULL;
1884 : : }
1885 : : }
1886 : :
1887 : : /* Move segment to appropriate bin if necessary. */
285 tmunro@postgresql.or 1888 [ + - ]:GBC 8 : if (segment_map->header != NULL)
1889 : 8 : rebin_segment(area, segment_map);
1890 : :
2690 rhaas@postgresql.org 1891 : 8 : LWLockRelease(DSA_AREA_LOCK(area));
1892 : :
1893 : : /*
1894 : : * Span-of-spans blocks store the span which describes them within the
1895 : : * block itself, so freeing the storage implicitly frees the descriptor
1896 : : * also. If this is a block of any other type, we need to separately free
1897 : : * the span object also. This recursive call to dsa_free will acquire the
1898 : : * span pool's lock. We can't deadlock because the acquisition order is
1899 : : * always some other pool and then the span pool.
1900 : : */
1901 [ + - ]: 8 : if (size_class != DSA_SCLASS_BLOCK_OF_SPANS)
1902 : 8 : dsa_free(area, span_pointer);
1903 : 8 : }
1904 : :
1905 : : static void
2690 rhaas@postgresql.org 1906 :CBC 2420 : unlink_span(dsa_area *area, dsa_area_span *span)
1907 : : {
1908 [ + + ]: 2420 : if (DsaPointerIsValid(span->nextspan))
1909 : : {
1910 : 1943 : dsa_area_span *next = dsa_get_address(area, span->nextspan);
1911 : :
1912 : 1943 : next->prevspan = span->prevspan;
1913 : : }
1914 [ + + ]: 2420 : if (DsaPointerIsValid(span->prevspan))
1915 : : {
1916 : 1437 : dsa_area_span *prev = dsa_get_address(area, span->prevspan);
1917 : :
1918 : 1437 : prev->nextspan = span->nextspan;
1919 : : }
1920 : : else
1921 : : {
1922 : 983 : dsa_area_pool *pool = dsa_get_address(area, span->pool);
1923 : :
1924 : 983 : pool->spans[span->fclass] = span->nextspan;
1925 : : }
1926 : 2420 : }
1927 : :
1928 : : static void
1929 : 91 : add_span_to_fullness_class(dsa_area *area, dsa_area_span *span,
1930 : : dsa_pointer span_pointer,
1931 : : int fclass)
1932 : : {
1933 : 91 : dsa_area_pool *pool = dsa_get_address(area, span->pool);
1934 : :
1935 [ + + ]: 91 : if (DsaPointerIsValid(pool->spans[fclass]))
1936 : : {
1937 : 33 : dsa_area_span *head = dsa_get_address(area,
1938 : : pool->spans[fclass]);
1939 : :
1940 : 33 : head->prevspan = span_pointer;
1941 : : }
1942 : 91 : span->prevspan = InvalidDsaPointer;
1943 : 91 : span->nextspan = pool->spans[fclass];
1944 : 91 : pool->spans[fclass] = span_pointer;
1945 : 91 : span->fclass = fclass;
1946 : 91 : }
1947 : :
1948 : : /*
1949 : : * Detach from an area that was either created or attached to by this process.
1950 : : */
1951 : : void
1952 : 21979 : dsa_detach(dsa_area *area)
1953 : : {
1954 : : int i;
1955 : :
1956 : : /* Detach from all segments. */
1957 [ + + ]: 60679 : for (i = 0; i <= area->high_segment_index; ++i)
1958 [ + + ]: 38700 : if (area->segment_maps[i].segment != NULL)
1959 : 16753 : dsm_detach(area->segment_maps[i].segment);
1960 : :
1961 : : /*
1962 : : * Note that 'detaching' (= detaching from DSM segments) doesn't include
1963 : : * 'releasing' (= adjusting the reference count). It would be nice to
1964 : : * combine these operations, but client code might never get around to
1965 : : * calling dsa_detach because of an error path, and a detach hook on any
1966 : : * particular segment is too late to detach other segments in the area
1967 : : * without risking a 'leak' warning in the non-error path.
1968 : : */
1969 : :
1970 : : /* Free the backend-local area object. */
1971 : 21979 : pfree(area);
1972 : 21979 : }
1973 : :
1974 : : /*
1975 : : * Unlink a segment from the bin that contains it.
1976 : : */
1977 : : static void
1978 : 2006 : unlink_segment(dsa_area *area, dsa_segment_map *segment_map)
1979 : : {
1980 [ + + ]: 2006 : if (segment_map->header->prev != DSA_SEGMENT_INDEX_NONE)
1981 : : {
1982 : : dsa_segment_map *prev;
1983 : :
2690 rhaas@postgresql.org 1984 :GBC 1 : prev = get_segment_by_index(area, segment_map->header->prev);
1985 : 1 : prev->header->next = segment_map->header->next;
1986 : : }
1987 : : else
1988 : : {
2690 rhaas@postgresql.org 1989 [ - + ]:CBC 2005 : Assert(area->control->segment_bins[segment_map->header->bin] ==
1990 : : get_segment_index(area, segment_map));
1991 : 2005 : area->control->segment_bins[segment_map->header->bin] =
1992 : 2005 : segment_map->header->next;
1993 : : }
1994 [ - + ]: 2006 : if (segment_map->header->next != DSA_SEGMENT_INDEX_NONE)
1995 : : {
1996 : : dsa_segment_map *next;
1997 : :
2690 rhaas@postgresql.org 1998 :UBC 0 : next = get_segment_by_index(area, segment_map->header->next);
1999 : 0 : next->header->prev = segment_map->header->prev;
2000 : : }
2690 rhaas@postgresql.org 2001 :CBC 2006 : }
2002 : :
2003 : : /*
2004 : : * Find a segment that could satisfy a request for 'npages' of contiguous
2005 : : * memory, or return NULL if none can be found. This may involve attaching to
2006 : : * segments that weren't previously attached so that we can query their free
2007 : : * pages map.
2008 : : */
2009 : : static dsa_segment_map *
2031 tmunro@postgresql.or 2010 : 11078 : get_best_segment(dsa_area *area, size_t npages)
2011 : : {
2012 : : size_t bin;
2013 : :
2690 rhaas@postgresql.org 2014 [ - + ]: 11078 : Assert(LWLockHeldByMe(DSA_AREA_LOCK(area)));
2033 tmunro@postgresql.or 2015 : 11078 : check_for_freed_segments_locked(area);
2016 : :
2017 : : /*
2018 : : * Start searching from the first bin that *might* have enough contiguous
2019 : : * pages.
2020 : : */
2690 rhaas@postgresql.org 2021 : 11078 : for (bin = contiguous_pages_to_segment_bin(npages);
2022 [ + + ]: 50176 : bin < DSA_NUM_SEGMENT_BINS;
2023 : 39098 : ++bin)
2024 : : {
2025 : : /*
2026 : : * The minimum contiguous size that any segment in this bin should
2027 : : * have. We'll re-bin if we see segments with fewer.
2028 : : */
2031 tmunro@postgresql.or 2029 : 49259 : size_t threshold = (size_t) 1 << (bin - 1);
2030 : : dsa_segment_index segment_index;
2031 : :
2032 : : /* Search this bin for a segment with enough contiguous space. */
2690 rhaas@postgresql.org 2033 : 49259 : segment_index = area->control->segment_bins[bin];
2034 [ + + ]: 50095 : while (segment_index != DSA_SEGMENT_INDEX_NONE)
2035 : : {
2036 : : dsa_segment_map *segment_map;
2037 : : dsa_segment_index next_segment_index;
2038 : : size_t contiguous_pages;
2039 : :
2040 : 10997 : segment_map = get_segment_by_index(area, segment_index);
2041 : 10997 : next_segment_index = segment_map->header->next;
2042 : 10997 : contiguous_pages = fpm_largest(segment_map->fpm);
2043 : :
2044 : : /* Not enough for the request, still enough for this bin. */
2045 [ + + - + ]: 10997 : if (contiguous_pages >= threshold && contiguous_pages < npages)
2046 : : {
2690 rhaas@postgresql.org 2047 :UBC 0 : segment_index = next_segment_index;
2048 : 0 : continue;
2049 : : }
2050 : :
2051 : : /* Re-bin it if it's no longer in the appropriate bin. */
2690 rhaas@postgresql.org 2052 [ + + ]:CBC 10997 : if (contiguous_pages < threshold)
2053 : : {
285 tmunro@postgresql.or 2054 : 1833 : rebin_segment(area, segment_map);
2055 : :
2056 : : /*
2057 : : * But fall through to see if it's enough to satisfy this
2058 : : * request anyway....
2059 : : */
2060 : : }
2061 : :
2062 : : /* Check if we are done. */
2690 rhaas@postgresql.org 2063 [ + + ]: 10997 : if (contiguous_pages >= npages)
2064 : 10161 : return segment_map;
2065 : :
2066 : : /* Continue searching the same bin. */
2067 : 836 : segment_index = next_segment_index;
2068 : : }
2069 : : }
2070 : :
2071 : : /* Not found. */
2072 : 917 : return NULL;
2073 : : }
2074 : :
2075 : : /*
2076 : : * Create a new segment that can handle at least requested_pages. Returns
2077 : : * NULL if the requested total size limit or maximum allowed number of
2078 : : * segments would be exceeded.
2079 : : */
2080 : : static dsa_segment_map *
2031 tmunro@postgresql.or 2081 : 917 : make_new_segment(dsa_area *area, size_t requested_pages)
2082 : : {
2083 : : dsa_segment_index new_index;
2084 : : size_t metadata_bytes;
2085 : : size_t total_size;
2086 : : size_t total_pages;
2087 : : size_t usable_pages;
2088 : : dsa_segment_map *segment_map;
2089 : : dsm_segment *segment;
2090 : : ResourceOwner oldowner;
2091 : :
2690 rhaas@postgresql.org 2092 [ - + ]: 917 : Assert(LWLockHeldByMe(DSA_AREA_LOCK(area)));
2093 : :
2094 : : /* Find a segment slot that is not in use (linearly for now). */
2095 [ + - ]: 947 : for (new_index = 1; new_index < DSA_MAX_SEGMENTS; ++new_index)
2096 : : {
2097 [ + + ]: 947 : if (area->control->segment_handles[new_index] == DSM_HANDLE_INVALID)
2098 : 917 : break;
2099 : : }
2100 [ - + ]: 917 : if (new_index == DSA_MAX_SEGMENTS)
2690 rhaas@postgresql.org 2101 :UBC 0 : return NULL;
2102 : :
2103 : : /*
2104 : : * If the total size limit is already exceeded, then we exit early and
2105 : : * avoid arithmetic wraparound in the unsigned expressions below.
2106 : : */
2690 rhaas@postgresql.org 2107 :CBC 917 : if (area->control->total_segment_size >=
2108 [ - + ]: 917 : area->control->max_total_segment_size)
2690 rhaas@postgresql.org 2109 :UBC 0 : return NULL;
2110 : :
2111 : : /*
2112 : : * The size should be at least as big as requested, and at least big
2113 : : * enough to follow a geometric series that approximately doubles the
2114 : : * total storage each time we create a new segment. We use geometric
2115 : : * growth because the underlying DSM system isn't designed for large
2116 : : * numbers of segments (otherwise we might even consider just using one
2117 : : * DSM segment for each large allocation and for each superblock, and then
2118 : : * we wouldn't need to use FreePageManager).
2119 : : *
2120 : : * We decide on a total segment size first, so that we produce tidy
2121 : : * power-of-two sized segments. This is a good property to have if we
2122 : : * move to huge pages in the future. Then we work back to the number of
2123 : : * pages we can fit.
2124 : : */
18 msawada@postgresql.o 2125 :GNC 917 : total_size = area->control->init_segment_size *
2031 tmunro@postgresql.or 2126 :CBC 917 : ((size_t) 1 << (new_index / DSA_NUM_SEGMENTS_AT_EACH_SIZE));
18 msawada@postgresql.o 2127 :GNC 917 : total_size = Min(total_size, area->control->max_segment_size);
2690 rhaas@postgresql.org 2128 :CBC 917 : total_size = Min(total_size,
2129 : : area->control->max_total_segment_size -
2130 : : area->control->total_segment_size);
2131 : :
2132 : 917 : total_pages = total_size / FPM_PAGE_SIZE;
2133 : 917 : metadata_bytes =
2134 : : MAXALIGN(sizeof(dsa_segment_header)) +
2135 : 917 : MAXALIGN(sizeof(FreePageManager)) +
2136 : : sizeof(dsa_pointer) * total_pages;
2137 : :
2138 : : /* Add padding up to next page boundary. */
2139 [ + - ]: 917 : if (metadata_bytes % FPM_PAGE_SIZE != 0)
2140 : 917 : metadata_bytes += FPM_PAGE_SIZE - (metadata_bytes % FPM_PAGE_SIZE);
2141 [ - + ]: 917 : if (total_size <= metadata_bytes)
2690 rhaas@postgresql.org 2142 :UBC 0 : return NULL;
2690 rhaas@postgresql.org 2143 :CBC 917 : usable_pages = (total_size - metadata_bytes) / FPM_PAGE_SIZE;
2144 [ - + ]: 917 : Assert(metadata_bytes + usable_pages * FPM_PAGE_SIZE <= total_size);
2145 : :
2146 : : /* See if that is enough... */
2147 [ - + ]: 917 : if (requested_pages > usable_pages)
2148 : : {
2149 : : /*
2150 : : * We'll make an odd-sized segment, working forward from the requested
2151 : : * number of pages.
2152 : : */
2690 rhaas@postgresql.org 2153 :UBC 0 : usable_pages = requested_pages;
2154 : 0 : metadata_bytes =
2155 : : MAXALIGN(sizeof(dsa_segment_header)) +
2156 : 0 : MAXALIGN(sizeof(FreePageManager)) +
2157 : : usable_pages * sizeof(dsa_pointer);
2158 : :
2159 : : /* Add padding up to next page boundary. */
2160 [ # # ]: 0 : if (metadata_bytes % FPM_PAGE_SIZE != 0)
2161 : 0 : metadata_bytes += FPM_PAGE_SIZE - (metadata_bytes % FPM_PAGE_SIZE);
2162 : 0 : total_size = metadata_bytes + usable_pages * FPM_PAGE_SIZE;
2163 : :
2164 : : /* Is that too large for dsa_pointer's addressing scheme? */
2165 [ # # ]: 0 : if (total_size > DSA_MAX_SEGMENT_SIZE)
2166 : 0 : return NULL;
2167 : :
2168 : : /* Would that exceed the limit? */
2169 : 0 : if (total_size > area->control->max_total_segment_size -
2170 [ # # ]: 0 : area->control->total_segment_size)
2171 : 0 : return NULL;
2172 : : }
2173 : :
2174 : : /* Create the segment. */
151 heikki.linnakangas@i 2175 :GNC 917 : oldowner = CurrentResourceOwner;
2176 : 917 : CurrentResourceOwner = area->resowner;
2690 rhaas@postgresql.org 2177 :CBC 917 : segment = dsm_create(total_size, 0);
151 heikki.linnakangas@i 2178 :GNC 917 : CurrentResourceOwner = oldowner;
2690 rhaas@postgresql.org 2179 [ - + ]:CBC 917 : if (segment == NULL)
2690 rhaas@postgresql.org 2180 :UBC 0 : return NULL;
2690 rhaas@postgresql.org 2181 :CBC 917 : dsm_pin_segment(segment);
2182 : :
2183 : : /* Store the handle in shared memory to be found by index. */
2184 : 1834 : area->control->segment_handles[new_index] =
2185 : 917 : dsm_segment_handle(segment);
2186 : : /* Track the highest segment index in the history of the area. */
2187 [ + - ]: 917 : if (area->control->high_segment_index < new_index)
2188 : 917 : area->control->high_segment_index = new_index;
2189 : : /* Track the highest segment index this backend has ever mapped. */
2190 [ + - ]: 917 : if (area->high_segment_index < new_index)
2191 : 917 : area->high_segment_index = new_index;
2192 : : /* Track total size of all segments. */
2193 : 917 : area->control->total_segment_size += total_size;
2194 [ - + ]: 917 : Assert(area->control->total_segment_size <=
2195 : : area->control->max_total_segment_size);
2196 : :
2197 : : /* Build a segment map for this segment in this backend. */
2198 : 917 : segment_map = &area->segment_maps[new_index];
2199 : 917 : segment_map->segment = segment;
2200 : 917 : segment_map->mapped_address = dsm_segment_address(segment);
2201 : 917 : segment_map->header = (dsa_segment_header *) segment_map->mapped_address;
2202 : 917 : segment_map->fpm = (FreePageManager *)
2203 : 917 : (segment_map->mapped_address +
2204 : : MAXALIGN(sizeof(dsa_segment_header)));
2205 : 917 : segment_map->pagemap = (dsa_pointer *)
2206 : 917 : (segment_map->mapped_address +
2207 : 917 : MAXALIGN(sizeof(dsa_segment_header)) +
2208 : : MAXALIGN(sizeof(FreePageManager)));
2209 : :
2210 : : /* Set up the free page map. */
2211 : 917 : FreePageManagerInitialize(segment_map->fpm, segment_map->mapped_address);
2212 : 917 : FreePageManagerPut(segment_map->fpm, metadata_bytes / FPM_PAGE_SIZE,
2213 : : usable_pages);
2214 : :
2215 : : /* Set up the segment header and put it in the appropriate bin. */
2216 : 917 : segment_map->header->magic =
2217 : 917 : DSA_SEGMENT_HEADER_MAGIC ^ area->control->handle ^ new_index;
2218 : 917 : segment_map->header->usable_pages = usable_pages;
2219 : 917 : segment_map->header->size = total_size;
2220 : 917 : segment_map->header->bin = contiguous_pages_to_segment_bin(usable_pages);
2221 : 917 : segment_map->header->prev = DSA_SEGMENT_INDEX_NONE;
2222 : 917 : segment_map->header->next =
2223 : 917 : area->control->segment_bins[segment_map->header->bin];
2224 : 917 : segment_map->header->freed = false;
2225 : 917 : area->control->segment_bins[segment_map->header->bin] = new_index;
2226 [ - + ]: 917 : if (segment_map->header->next != DSA_SEGMENT_INDEX_NONE)
2227 : : {
2228 : : dsa_segment_map *next =
331 tgl@sss.pgh.pa.us 2229 :UBC 0 : get_segment_by_index(area, segment_map->header->next);
2230 : :
2690 rhaas@postgresql.org 2231 [ # # ]: 0 : Assert(next->header->bin == segment_map->header->bin);
2232 : 0 : next->header->prev = new_index;
2233 : : }
2234 : :
2690 rhaas@postgresql.org 2235 :CBC 917 : return segment_map;
2236 : : }
2237 : :
2238 : : /*
2239 : : * Check if any segments have been freed by destroy_superblock, so we can
2240 : : * detach from them in this backend. This function is called by
2241 : : * dsa_get_address and dsa_free to make sure that a dsa_pointer they have
2242 : : * received can be resolved to the correct segment.
2243 : : *
2244 : : * The danger we want to defend against is that there could be an old segment
2245 : : * mapped into a given slot in this backend, and the dsa_pointer they have
2246 : : * might refer to some new segment in the same slot. So those functions must
2247 : : * be sure to process all instructions to detach from a freed segment that had
2248 : : * been generated by the time this process received the dsa_pointer, before
2249 : : * they call get_segment_by_index.
2250 : : */
2251 : : static void
2252 : 9196672 : check_for_freed_segments(dsa_area *area)
2253 : : {
2254 : : size_t freed_segment_counter;
2255 : :
2256 : : /*
2257 : : * Any other process that has freed a segment has incremented
2258 : : * freed_segment_counter while holding an LWLock, and that must precede
2259 : : * any backend creating a new segment in the same slot while holding an
2260 : : * LWLock, and that must precede the creation of any dsa_pointer pointing
2261 : : * into the new segment which might reach us here, and the caller must
2262 : : * have sent the dsa_pointer to this process using appropriate memory
2263 : : * synchronization (some kind of locking or atomic primitive or system
2264 : : * call). So all we need to do on the reading side is ask for the load of
2265 : : * freed_segment_counter to follow the caller's load of the dsa_pointer it
2266 : : * has, and we can be sure to detect any segments that had been freed as
2267 : : * of the time that the dsa_pointer reached this process.
2268 : : */
2269 : 9196672 : pg_read_barrier();
2270 : 9196672 : freed_segment_counter = area->control->freed_segment_counter;
2271 [ - + ]: 9196672 : if (unlikely(area->freed_segment_counter != freed_segment_counter))
2272 : : {
2273 : : /* Check all currently mapped segments to find what's been freed. */
2690 rhaas@postgresql.org 2274 :UBC 0 : LWLockAcquire(DSA_AREA_LOCK(area), LW_EXCLUSIVE);
2033 tmunro@postgresql.or 2275 : 0 : check_for_freed_segments_locked(area);
2276 : 0 : LWLockRelease(DSA_AREA_LOCK(area));
2277 : : }
2033 tmunro@postgresql.or 2278 :CBC 9196672 : }
2279 : :
2280 : : /*
2281 : : * Workhorse for check_for_freed_segments(), and also used directly in path
2282 : : * where the area lock is already held. This should be called after acquiring
2283 : : * the lock but before looking up any segment by index number, to make sure we
2284 : : * unmap any stale segments that might have previously had the same index as a
2285 : : * current segment.
2286 : : */
2287 : : static void
2288 : 11086 : check_for_freed_segments_locked(dsa_area *area)
2289 : : {
2290 : : size_t freed_segment_counter;
2291 : : int i;
2292 : :
2293 [ - + ]: 11086 : Assert(LWLockHeldByMe(DSA_AREA_LOCK(area)));
2294 : 11086 : freed_segment_counter = area->control->freed_segment_counter;
2295 [ - + ]: 11086 : if (unlikely(area->freed_segment_counter != freed_segment_counter))
2296 : : {
2690 rhaas@postgresql.org 2297 [ # # ]:UBC 0 : for (i = 0; i <= area->high_segment_index; ++i)
2298 : : {
2299 [ # # ]: 0 : if (area->segment_maps[i].header != NULL &&
2300 [ # # ]: 0 : area->segment_maps[i].header->freed)
2301 : : {
2302 : 0 : dsm_detach(area->segment_maps[i].segment);
2303 : 0 : area->segment_maps[i].segment = NULL;
2304 : 0 : area->segment_maps[i].header = NULL;
2305 : 0 : area->segment_maps[i].mapped_address = NULL;
2306 : : }
2307 : : }
2308 : 0 : area->freed_segment_counter = freed_segment_counter;
2309 : : }
2690 rhaas@postgresql.org 2310 :CBC 11086 : }
2311 : :
2312 : : /*
2313 : : * Re-bin segment if it's no longer in the appropriate bin.
2314 : : */
2315 : : static void
285 tmunro@postgresql.or 2316 : 4162 : rebin_segment(dsa_area *area, dsa_segment_map *segment_map)
2317 : : {
2318 : : size_t new_bin;
2319 : : dsa_segment_index segment_index;
2320 : :
2321 : 4162 : new_bin = contiguous_pages_to_segment_bin(fpm_largest(segment_map->fpm));
2322 [ + + ]: 4162 : if (segment_map->header->bin == new_bin)
2323 : 2156 : return;
2324 : :
2325 : : /* Remove it from its current bin. */
2326 : 2006 : unlink_segment(area, segment_map);
2327 : :
2328 : : /* Push it onto the front of its new bin. */
2329 : 2006 : segment_index = get_segment_index(area, segment_map);
2330 : 2006 : segment_map->header->prev = DSA_SEGMENT_INDEX_NONE;
2331 : 2006 : segment_map->header->next = area->control->segment_bins[new_bin];
2332 : 2006 : segment_map->header->bin = new_bin;
2333 : 2006 : area->control->segment_bins[new_bin] = segment_index;
2334 [ + + ]: 2006 : if (segment_map->header->next != DSA_SEGMENT_INDEX_NONE)
2335 : : {
2336 : : dsa_segment_map *next;
2337 : :
285 tmunro@postgresql.or 2338 :GBC 5 : next = get_segment_by_index(area, segment_map->header->next);
2339 [ - + ]: 5 : Assert(next->header->bin == new_bin);
2340 : 5 : next->header->prev = segment_index;
2341 : : }
2342 : : }
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