Age Owner Branch data TLA Line data Source code
1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * slab.c
4 : : * SLAB allocator definitions.
5 : : *
6 : : * SLAB is a MemoryContext implementation designed for cases where large
7 : : * numbers of equally-sized objects can be allocated and freed efficiently
8 : : * with minimal memory wastage and fragmentation.
9 : : *
10 : : *
11 : : * Portions Copyright (c) 2017-2024, PostgreSQL Global Development Group
12 : : *
13 : : * IDENTIFICATION
14 : : * src/backend/utils/mmgr/slab.c
15 : : *
16 : : *
17 : : * NOTE:
18 : : * The constant allocation size allows significant simplification and various
19 : : * optimizations over more general purpose allocators. The blocks are carved
20 : : * into chunks of exactly the right size, wasting only the space required to
21 : : * MAXALIGN the allocated chunks.
22 : : *
23 : : * Slab can also help reduce memory fragmentation in cases where longer-lived
24 : : * chunks remain stored on blocks while most of the other chunks have already
25 : : * been pfree'd. We give priority to putting new allocations into the
26 : : * "fullest" block. This help avoid having too many sparsely used blocks
27 : : * around and allows blocks to more easily become completely unused which
28 : : * allows them to be eventually free'd.
29 : : *
30 : : * We identify the "fullest" block to put new allocations on by using a block
31 : : * from the lowest populated element of the context's "blocklist" array.
32 : : * This is an array of dlists containing blocks which we partition by the
33 : : * number of free chunks which block has. Blocks with fewer free chunks are
34 : : * stored in a lower indexed dlist array slot. Full blocks go on the 0th
35 : : * element of the blocklist array. So that we don't have to have too many
36 : : * elements in the array, each dlist in the array is responsible for a range
37 : : * of free chunks. When a chunk is palloc'd or pfree'd we may need to move
38 : : * the block onto another dlist if the number of free chunks crosses the
39 : : * range boundary that the current list is responsible for. Having just a
40 : : * few blocklist elements reduces the number of times we must move the block
41 : : * onto another dlist element.
42 : : *
43 : : * We keep track of free chunks within each block by using a block-level free
44 : : * list. We consult this list when we allocate a new chunk in the block.
45 : : * The free list is a linked list, the head of which is pointed to with
46 : : * SlabBlock's freehead field. Each subsequent list item is stored in the
47 : : * free chunk's memory. We ensure chunks are large enough to store this
48 : : * address.
49 : : *
50 : : * When we allocate a new block, technically all chunks are free, however, to
51 : : * avoid having to write out the entire block to set the linked list for the
52 : : * free chunks for every chunk in the block, we instead store a pointer to
53 : : * the next "unused" chunk on the block and keep track of how many of these
54 : : * unused chunks there are. When a new block is malloc'd, all chunks are
55 : : * unused. The unused pointer starts with the first chunk on the block and
56 : : * as chunks are allocated, the unused pointer is incremented. As chunks are
57 : : * pfree'd, the unused pointer never goes backwards. The unused pointer can
58 : : * be thought of as a high watermark for the maximum number of chunks in the
59 : : * block which have been in use concurrently. When a chunk is pfree'd the
60 : : * chunk is put onto the head of the free list and the unused pointer is not
61 : : * changed. We only consume more unused chunks if we run out of free chunks
62 : : * on the free list. This method effectively gives priority to using
63 : : * previously used chunks over previously unused chunks, which should perform
64 : : * better due to CPU caching effects.
65 : : *
66 : : *-------------------------------------------------------------------------
67 : : */
68 : :
69 : : #include "postgres.h"
70 : :
71 : : #include "lib/ilist.h"
72 : : #include "utils/memdebug.h"
73 : : #include "utils/memutils.h"
74 : : #include "utils/memutils_internal.h"
75 : : #include "utils/memutils_memorychunk.h"
76 : :
77 : : #define Slab_BLOCKHDRSZ MAXALIGN(sizeof(SlabBlock))
78 : :
79 : : #ifdef MEMORY_CONTEXT_CHECKING
80 : : /*
81 : : * Size of the memory required to store the SlabContext.
82 : : * MEMORY_CONTEXT_CHECKING builds need some extra memory for the isChunkFree
83 : : * array.
84 : : */
85 : : #define Slab_CONTEXT_HDRSZ(chunksPerBlock) \
86 : : (sizeof(SlabContext) + ((chunksPerBlock) * sizeof(bool)))
87 : : #else
88 : : #define Slab_CONTEXT_HDRSZ(chunksPerBlock) sizeof(SlabContext)
89 : : #endif
90 : :
91 : : /*
92 : : * The number of partitions to divide the blocklist into based their number of
93 : : * free chunks. There must be at least 2.
94 : : */
95 : : #define SLAB_BLOCKLIST_COUNT 3
96 : :
97 : : /* The maximum number of completely empty blocks to keep around for reuse. */
98 : : #define SLAB_MAXIMUM_EMPTY_BLOCKS 10
99 : :
100 : : /*
101 : : * SlabContext is a specialized implementation of MemoryContext.
102 : : */
103 : : typedef struct SlabContext
104 : : {
105 : : MemoryContextData header; /* Standard memory-context fields */
106 : : /* Allocation parameters for this context: */
107 : : uint32 chunkSize; /* the requested (non-aligned) chunk size */
108 : : uint32 fullChunkSize; /* chunk size with chunk header and alignment */
109 : : uint32 blockSize; /* the size to make each block of chunks */
110 : : int32 chunksPerBlock; /* number of chunks that fit in 1 block */
111 : : int32 curBlocklistIndex; /* index into the blocklist[] element
112 : : * containing the fullest, blocks */
113 : : #ifdef MEMORY_CONTEXT_CHECKING
114 : : bool *isChunkFree; /* array to mark free chunks in a block during
115 : : * SlabCheck */
116 : : #endif
117 : :
118 : : int32 blocklist_shift; /* number of bits to shift the nfree count
119 : : * by to get the index into blocklist[] */
120 : : dclist_head emptyblocks; /* empty blocks to use up first instead of
121 : : * mallocing new blocks */
122 : :
123 : : /*
124 : : * Blocks with free space, grouped by the number of free chunks they
125 : : * contain. Completely full blocks are stored in the 0th element.
126 : : * Completely empty blocks are stored in emptyblocks or free'd if we have
127 : : * enough empty blocks already.
128 : : */
129 : : dlist_head blocklist[SLAB_BLOCKLIST_COUNT];
130 : : } SlabContext;
131 : :
132 : : /*
133 : : * SlabBlock
134 : : * Structure of a single slab block.
135 : : *
136 : : * slab: pointer back to the owning MemoryContext
137 : : * nfree: number of chunks on the block which are unallocated
138 : : * nunused: number of chunks on the block unallocated and not on the block's
139 : : * freelist.
140 : : * freehead: linked-list header storing a pointer to the first free chunk on
141 : : * the block. Subsequent pointers are stored in the chunk's memory. NULL
142 : : * indicates the end of the list.
143 : : * unused: pointer to the next chunk which has yet to be used.
144 : : * node: doubly-linked list node for the context's blocklist
145 : : */
146 : : typedef struct SlabBlock
147 : : {
148 : : SlabContext *slab; /* owning context */
149 : : int32 nfree; /* number of chunks on free + unused chunks */
150 : : int32 nunused; /* number of unused chunks */
151 : : MemoryChunk *freehead; /* pointer to the first free chunk */
152 : : MemoryChunk *unused; /* pointer to the next unused chunk */
153 : : dlist_node node; /* doubly-linked list for blocklist[] */
154 : : } SlabBlock;
155 : :
156 : :
157 : : #define Slab_CHUNKHDRSZ sizeof(MemoryChunk)
158 : : #define SlabChunkGetPointer(chk) \
159 : : ((void *) (((char *) (chk)) + sizeof(MemoryChunk)))
160 : :
161 : : /*
162 : : * SlabBlockGetChunk
163 : : * Obtain a pointer to the nth (0-based) chunk in the block
164 : : */
165 : : #define SlabBlockGetChunk(slab, block, n) \
166 : : ((MemoryChunk *) ((char *) (block) + Slab_BLOCKHDRSZ \
167 : : + ((n) * (slab)->fullChunkSize)))
168 : :
169 : : #if defined(MEMORY_CONTEXT_CHECKING) || defined(USE_ASSERT_CHECKING)
170 : :
171 : : /*
172 : : * SlabChunkIndex
173 : : * Get the 0-based index of how many chunks into the block the given
174 : : * chunk is.
175 : : */
176 : : #define SlabChunkIndex(slab, block, chunk) \
177 : : (((char *) (chunk) - (char *) SlabBlockGetChunk(slab, block, 0)) / \
178 : : (slab)->fullChunkSize)
179 : :
180 : : /*
181 : : * SlabChunkMod
182 : : * A MemoryChunk should always be at an address which is a multiple of
183 : : * fullChunkSize starting from the 0th chunk position. This will return
184 : : * non-zero if it's not.
185 : : */
186 : : #define SlabChunkMod(slab, block, chunk) \
187 : : (((char *) (chunk) - (char *) SlabBlockGetChunk(slab, block, 0)) % \
188 : : (slab)->fullChunkSize)
189 : :
190 : : #endif
191 : :
192 : : /*
193 : : * SlabIsValid
194 : : * True iff set is a valid slab allocation set.
195 : : */
196 : : #define SlabIsValid(set) (PointerIsValid(set) && IsA(set, SlabContext))
197 : :
198 : : /*
199 : : * SlabBlockIsValid
200 : : * True iff block is a valid block of slab allocation set.
201 : : */
202 : : #define SlabBlockIsValid(block) \
203 : : (PointerIsValid(block) && SlabIsValid((block)->slab))
204 : :
205 : : /*
206 : : * SlabBlocklistIndex
207 : : * Determine the blocklist index that a block should be in for the given
208 : : * number of free chunks.
209 : : */
210 : : static inline int32
481 drowley@postgresql.o 211 :CBC 9032590 : SlabBlocklistIndex(SlabContext *slab, int nfree)
212 : : {
213 : : int32 index;
214 : 9032590 : int32 blocklist_shift = slab->blocklist_shift;
215 : :
216 [ + - - + ]: 9032590 : Assert(nfree >= 0 && nfree <= slab->chunksPerBlock);
217 : :
218 : : /*
219 : : * Determine the blocklist index based on the number of free chunks. We
220 : : * must ensure that 0 free chunks is dedicated to index 0. Everything
221 : : * else must be >= 1 and < SLAB_BLOCKLIST_COUNT.
222 : : *
223 : : * To make this as efficient as possible, we exploit some two's complement
224 : : * arithmetic where we reverse the sign before bit shifting. This results
225 : : * in an nfree of 0 using index 0 and anything non-zero staying non-zero.
226 : : * This is exploiting 0 and -0 being the same in two's complement. When
227 : : * we're done, we just need to flip the sign back over again for a
228 : : * positive index.
229 : : */
230 : 9032590 : index = -((-nfree) >> blocklist_shift);
231 : :
232 [ + + ]: 9032590 : if (nfree == 0)
233 [ - + ]: 47680 : Assert(index == 0);
234 : : else
235 [ + - - + ]: 8984910 : Assert(index >= 1 && index < SLAB_BLOCKLIST_COUNT);
236 : :
237 : 9032590 : return index;
238 : : }
239 : :
240 : : /*
241 : : * SlabFindNextBlockListIndex
242 : : * Search blocklist for blocks which have free chunks and return the
243 : : * index of the blocklist found containing at least 1 block with free
244 : : * chunks. If no block can be found we return 0.
245 : : *
246 : : * Note: We give priority to fuller blocks so that these are filled before
247 : : * emptier blocks. This is done to increase the chances that mostly-empty
248 : : * blocks will eventually become completely empty so they can be free'd.
249 : : */
250 : : static int32
251 : 103034 : SlabFindNextBlockListIndex(SlabContext *slab)
252 : : {
253 : : /* start at 1 as blocklist[0] is for full blocks. */
254 [ + + ]: 169483 : for (int i = 1; i < SLAB_BLOCKLIST_COUNT; i++)
255 : : {
256 : : /* return the first found non-empty index */
257 [ + + ]: 140037 : if (!dlist_is_empty(&slab->blocklist[i]))
258 : 73588 : return i;
259 : : }
260 : :
261 : : /* no blocks with free space */
262 : 29446 : return 0;
263 : : }
264 : :
265 : : /*
266 : : * SlabGetNextFreeChunk
267 : : * Return the next free chunk in block and update the block to account
268 : : * for the returned chunk now being used.
269 : : */
270 : : static inline MemoryChunk *
271 : 1758170 : SlabGetNextFreeChunk(SlabContext *slab, SlabBlock *block)
272 : : {
273 : : MemoryChunk *chunk;
274 : :
275 [ - + ]: 1758170 : Assert(block->nfree > 0);
276 : :
277 [ + + ]: 1758170 : if (block->freehead != NULL)
278 : : {
279 : 1559237 : chunk = block->freehead;
280 : :
281 : : /*
282 : : * Pop the chunk from the linked list of free chunks. The pointer to
283 : : * the next free chunk is stored in the chunk itself.
284 : : */
285 : : VALGRIND_MAKE_MEM_DEFINED(SlabChunkGetPointer(chunk), sizeof(MemoryChunk *));
286 : 1559237 : block->freehead = *(MemoryChunk **) SlabChunkGetPointer(chunk);
287 : :
288 : : /* check nothing stomped on the free chunk's memory */
289 [ + + + - : 1559237 : Assert(block->freehead == NULL ||
+ - - + ]
290 : : (block->freehead >= SlabBlockGetChunk(slab, block, 0) &&
291 : : block->freehead <= SlabBlockGetChunk(slab, block, slab->chunksPerBlock - 1) &&
292 : : SlabChunkMod(slab, block, block->freehead) == 0));
293 : : }
294 : : else
295 : : {
296 [ - + ]: 198933 : Assert(block->nunused > 0);
297 : :
298 : 198933 : chunk = block->unused;
299 : 198933 : block->unused = (MemoryChunk *) (((char *) block->unused) + slab->fullChunkSize);
300 : 198933 : block->nunused--;
301 : : }
302 : :
303 : 1758170 : block->nfree--;
304 : :
305 : 1758170 : return chunk;
306 : : }
307 : :
308 : : /*
309 : : * SlabContextCreate
310 : : * Create a new Slab context.
311 : : *
312 : : * parent: parent context, or NULL if top-level context
313 : : * name: name of context (must be statically allocated)
314 : : * blockSize: allocation block size
315 : : * chunkSize: allocation chunk size
316 : : *
317 : : * The Slab_CHUNKHDRSZ + MAXALIGN(chunkSize + 1) may not exceed
318 : : * MEMORYCHUNK_MAX_VALUE.
319 : : * 'blockSize' may not exceed MEMORYCHUNK_MAX_BLOCKOFFSET.
320 : : */
321 : : MemoryContext
2603 andres@anarazel.de 322 : 423758 : SlabContextCreate(MemoryContext parent,
323 : : const char *name,
324 : : Size blockSize,
325 : : Size chunkSize)
326 : : {
327 : : int chunksPerBlock;
328 : : Size fullChunkSize;
329 : : SlabContext *slab;
330 : : int i;
331 : :
332 : : /* ensure MemoryChunk's size is properly maxaligned */
333 : : StaticAssertDecl(Slab_CHUNKHDRSZ == MAXALIGN(Slab_CHUNKHDRSZ),
334 : : "sizeof(MemoryChunk) is not maxaligned");
272 drowley@postgresql.o 335 [ - + ]:GNC 423758 : Assert(blockSize <= MEMORYCHUNK_MAX_BLOCKOFFSET);
336 : :
337 : : /*
338 : : * Ensure there's enough space to store the pointer to the next free chunk
339 : : * in the memory of the (otherwise) unused allocation.
340 : : */
481 drowley@postgresql.o 341 [ - + ]:CBC 423758 : if (chunkSize < sizeof(MemoryChunk *))
481 drowley@postgresql.o 342 :UBC 0 : chunkSize = sizeof(MemoryChunk *);
343 : :
344 : : /* length of the maxaligned chunk including the chunk header */
345 : : #ifdef MEMORY_CONTEXT_CHECKING
346 : : /* ensure there's always space for the sentinel byte */
585 drowley@postgresql.o 347 :CBC 423758 : fullChunkSize = Slab_CHUNKHDRSZ + MAXALIGN(chunkSize + 1);
348 : : #else
349 : : fullChunkSize = Slab_CHUNKHDRSZ + MAXALIGN(chunkSize);
350 : : #endif
351 : :
272 drowley@postgresql.o 352 [ - + ]:GNC 423758 : Assert(fullChunkSize <= MEMORYCHUNK_MAX_VALUE);
353 : :
354 : : /* compute the number of chunks that will fit on each block */
593 drowley@postgresql.o 355 :CBC 423758 : chunksPerBlock = (blockSize - Slab_BLOCKHDRSZ) / fullChunkSize;
356 : :
357 : : /* Make sure the block can store at least one chunk. */
481 358 [ - + ]: 423758 : if (chunksPerBlock == 0)
481 drowley@postgresql.o 359 [ # # ]:UBC 0 : elog(ERROR, "block size %zu for slab is too small for %zu-byte chunks",
360 : : blockSize, chunkSize);
361 : :
362 : :
363 : :
481 drowley@postgresql.o 364 :CBC 423758 : slab = (SlabContext *) malloc(Slab_CONTEXT_HDRSZ(chunksPerBlock));
2314 tgl@sss.pgh.pa.us 365 [ - + ]: 423758 : if (slab == NULL)
366 : : {
2314 tgl@sss.pgh.pa.us 367 :UBC 0 : MemoryContextStats(TopMemoryContext);
368 [ # # ]: 0 : ereport(ERROR,
369 : : (errcode(ERRCODE_OUT_OF_MEMORY),
370 : : errmsg("out of memory"),
371 : : errdetail("Failed while creating memory context \"%s\".",
372 : : name)));
373 : : }
374 : :
375 : : /*
376 : : * Avoid writing code that can fail between here and MemoryContextCreate;
377 : : * we'd leak the header if we ereport in this stretch.
378 : : */
379 : :
380 : : /* Fill in SlabContext-specific header fields */
272 drowley@postgresql.o 381 :GNC 423758 : slab->chunkSize = (uint32) chunkSize;
382 : 423758 : slab->fullChunkSize = (uint32) fullChunkSize;
383 : 423758 : slab->blockSize = (uint32) blockSize;
2603 andres@anarazel.de 384 :CBC 423758 : slab->chunksPerBlock = chunksPerBlock;
481 drowley@postgresql.o 385 : 423758 : slab->curBlocklistIndex = 0;
386 : :
387 : : /*
388 : : * Compute a shift that guarantees that shifting chunksPerBlock with it is
389 : : * < SLAB_BLOCKLIST_COUNT - 1. The reason that we subtract 1 from
390 : : * SLAB_BLOCKLIST_COUNT in this calculation is that we reserve the 0th
391 : : * blocklist element for blocks which have no free chunks.
392 : : *
393 : : * We calculate the number of bits to shift by rather than a divisor to
394 : : * divide by as performing division each time we need to find the
395 : : * blocklist index would be much slower.
396 : : */
397 : 423758 : slab->blocklist_shift = 0;
398 [ + + ]: 2626918 : while ((slab->chunksPerBlock >> slab->blocklist_shift) >= (SLAB_BLOCKLIST_COUNT - 1))
399 : 2203160 : slab->blocklist_shift++;
400 : :
401 : : /* initialize the list to store empty blocks to be reused */
402 : 423758 : dclist_init(&slab->emptyblocks);
403 : :
404 : : /* initialize each blocklist slot */
405 [ + + ]: 1695032 : for (i = 0; i < SLAB_BLOCKLIST_COUNT; i++)
406 : 1271274 : dlist_init(&slab->blocklist[i]);
407 : :
408 : : #ifdef MEMORY_CONTEXT_CHECKING
409 : : /* set the isChunkFree pointer right after the end of the context */
410 : 423758 : slab->isChunkFree = (bool *) ((char *) slab + sizeof(SlabContext));
411 : : #endif
412 : :
413 : : /* Finally, do the type-independent part of context creation */
2314 tgl@sss.pgh.pa.us 414 : 423758 : MemoryContextCreate((MemoryContext) slab,
415 : : T_SlabContext,
416 : : MCTX_SLAB_ID,
417 : : parent,
418 : : name);
419 : :
420 : 423758 : return (MemoryContext) slab;
421 : : }
422 : :
423 : : /*
424 : : * SlabReset
425 : : * Frees all memory which is allocated in the given set.
426 : : *
427 : : * The code simply frees all the blocks in the context - we don't keep any
428 : : * keeper blocks or anything like that.
429 : : */
430 : : void
2603 andres@anarazel.de 431 : 423410 : SlabReset(MemoryContext context)
432 : : {
552 tgl@sss.pgh.pa.us 433 : 423410 : SlabContext *slab = (SlabContext *) context;
434 : : dlist_mutable_iter miter;
435 : : int i;
436 : :
534 peter@eisentraut.org 437 [ + - - + ]: 423410 : Assert(SlabIsValid(slab));
438 : :
439 : : #ifdef MEMORY_CONTEXT_CHECKING
440 : : /* Check for corruption and leaks before freeing */
2603 andres@anarazel.de 441 : 423410 : SlabCheck(context);
442 : : #endif
443 : :
444 : : /* release any retained empty blocks */
481 drowley@postgresql.o 445 [ + - + + ]: 424758 : dclist_foreach_modify(miter, &slab->emptyblocks)
446 : : {
447 : 1348 : SlabBlock *block = dlist_container(SlabBlock, node, miter.cur);
448 : :
449 : 1348 : dclist_delete_from(&slab->emptyblocks, miter.cur);
450 : :
451 : : #ifdef CLOBBER_FREED_MEMORY
452 : 1348 : wipe_mem(block, slab->blockSize);
453 : : #endif
454 : 1348 : free(block);
455 : 1348 : context->mem_allocated -= slab->blockSize;
456 : : }
457 : :
458 : : /* walk over blocklist and free the blocks */
459 [ + + ]: 1693640 : for (i = 0; i < SLAB_BLOCKLIST_COUNT; i++)
460 : : {
461 [ + - + + ]: 1354673 : dlist_foreach_modify(miter, &slab->blocklist[i])
462 : : {
2603 andres@anarazel.de 463 : 84443 : SlabBlock *block = dlist_container(SlabBlock, node, miter.cur);
464 : :
465 : 84443 : dlist_delete(miter.cur);
466 : :
467 : : #ifdef CLOBBER_FREED_MEMORY
468 : 84443 : wipe_mem(block, slab->blockSize);
469 : : #endif
470 : 84443 : free(block);
1487 jdavis@postgresql.or 471 : 84443 : context->mem_allocated -= slab->blockSize;
472 : : }
473 : : }
474 : :
481 drowley@postgresql.o 475 : 423410 : slab->curBlocklistIndex = 0;
476 : :
1487 jdavis@postgresql.or 477 [ - + ]: 423410 : Assert(context->mem_allocated == 0);
2603 andres@anarazel.de 478 : 423410 : }
479 : :
480 : : /*
481 : : * SlabDelete
482 : : * Free all memory which is allocated in the given context.
483 : : */
484 : : void
485 : 423410 : SlabDelete(MemoryContext context)
486 : : {
487 : : /* Reset to release all the SlabBlocks */
488 : 423410 : SlabReset(context);
489 : : /* And free the context header */
2314 tgl@sss.pgh.pa.us 490 : 423410 : free(context);
2603 andres@anarazel.de 491 : 423410 : }
492 : :
493 : : /*
494 : : * Small helper for allocating a new chunk from a chunk, to avoid duplicating
495 : : * the code between SlabAlloc() and SlabAllocFromNewBlock().
496 : : */
497 : : static inline void *
41 drowley@postgresql.o 498 :GNC 1846282 : SlabAllocSetupNewChunk(MemoryContext context, SlabBlock *block,
499 : : MemoryChunk *chunk, Size size)
500 : : {
501 : 1846282 : SlabContext *slab = (SlabContext *) context;
502 : :
503 : : /*
504 : : * Check that the chunk pointer is actually somewhere on the block and is
505 : : * aligned as expected.
506 : : */
507 [ - + ]: 1846282 : Assert(chunk >= SlabBlockGetChunk(slab, block, 0));
508 [ - + ]: 1846282 : Assert(chunk <= SlabBlockGetChunk(slab, block, slab->chunksPerBlock - 1));
509 [ - + ]: 1846282 : Assert(SlabChunkMod(slab, block, chunk) == 0);
510 : :
511 : : /* Prepare to initialize the chunk header. */
512 : : VALGRIND_MAKE_MEM_UNDEFINED(chunk, Slab_CHUNKHDRSZ);
513 : :
514 : 1846282 : MemoryChunkSetHdrMask(chunk, block, MAXALIGN(slab->chunkSize), MCTX_SLAB_ID);
515 : :
516 : : #ifdef MEMORY_CONTEXT_CHECKING
517 : : /* slab mark to catch clobber of "unused" space */
518 [ - + ]: 1846282 : Assert(slab->chunkSize < (slab->fullChunkSize - Slab_CHUNKHDRSZ));
519 : 1846282 : set_sentinel(MemoryChunkGetPointer(chunk), size);
520 : : VALGRIND_MAKE_MEM_NOACCESS(((char *) chunk) + Slab_CHUNKHDRSZ +
521 : : slab->chunkSize,
522 : : slab->fullChunkSize -
523 : : (slab->chunkSize + Slab_CHUNKHDRSZ));
524 : : #endif
525 : :
526 : : #ifdef RANDOMIZE_ALLOCATED_MEMORY
527 : : /* fill the allocated space with junk */
528 : : randomize_mem((char *) MemoryChunkGetPointer(chunk), size);
529 : : #endif
530 : :
531 : : /* Disallow access to the chunk header. */
532 : : VALGRIND_MAKE_MEM_NOACCESS(chunk, Slab_CHUNKHDRSZ);
533 : :
534 : 1846282 : return MemoryChunkGetPointer(chunk);
535 : : }
536 : :
537 : : pg_noinline
538 : : static void *
539 : 113877 : SlabAllocFromNewBlock(MemoryContext context, Size size, int flags)
540 : : {
541 : 113877 : SlabContext *slab = (SlabContext *) context;
542 : : SlabBlock *block;
543 : : MemoryChunk *chunk;
544 : : dlist_head *blocklist;
545 : : int blocklist_idx;
546 : :
547 : : /* to save allocating a new one, first check the empty blocks list */
548 [ + + ]: 113877 : if (dclist_count(&slab->emptyblocks) > 0)
549 : : {
550 : 25765 : dlist_node *node = dclist_pop_head_node(&slab->emptyblocks);
551 : :
552 : 25765 : block = dlist_container(SlabBlock, node, node);
553 : :
554 : : /*
555 : : * SlabFree() should have left this block in a valid state with all
556 : : * chunks free. Ensure that's the case.
557 : : */
558 [ - + ]: 25765 : Assert(block->nfree == slab->chunksPerBlock);
559 : :
560 : : /* fetch the next chunk from this block */
561 : 25765 : chunk = SlabGetNextFreeChunk(slab, block);
562 : : }
563 : : else
564 : : {
565 : 88112 : block = (SlabBlock *) malloc(slab->blockSize);
566 : :
567 [ - + ]: 88112 : if (unlikely(block == NULL))
41 drowley@postgresql.o 568 :UNC 0 : return MemoryContextAllocationFailure(context, size, flags);
569 : :
41 drowley@postgresql.o 570 :GNC 88112 : block->slab = slab;
571 : 88112 : context->mem_allocated += slab->blockSize;
572 : :
573 : : /* use the first chunk in the new block */
574 : 88112 : chunk = SlabBlockGetChunk(slab, block, 0);
575 : :
576 : 88112 : block->nfree = slab->chunksPerBlock - 1;
577 : 88112 : block->unused = SlabBlockGetChunk(slab, block, 1);
578 : 88112 : block->freehead = NULL;
579 : 88112 : block->nunused = slab->chunksPerBlock - 1;
580 : : }
581 : :
582 : : /* find the blocklist element for storing blocks with 1 used chunk */
583 : 113877 : blocklist_idx = SlabBlocklistIndex(slab, block->nfree);
584 : 113877 : blocklist = &slab->blocklist[blocklist_idx];
585 : :
586 : : /* this better be empty. We just added a block thinking it was */
587 [ - + ]: 113877 : Assert(dlist_is_empty(blocklist));
588 : :
589 : 113877 : dlist_push_head(blocklist, &block->node);
590 : :
591 : 113877 : slab->curBlocklistIndex = blocklist_idx;
592 : :
593 : 113877 : return SlabAllocSetupNewChunk(context, block, chunk, size);
594 : : }
595 : :
596 : : /*
597 : : * SlabAllocInvalidSize
598 : : * Handle raising an ERROR for an invalid size request. We don't do this
599 : : * in slab alloc as calling the elog functions would force the compiler
600 : : * to setup the stack frame in SlabAlloc. For performance reasons, we
601 : : * want to avoid that.
602 : : */
603 : : pg_noinline
604 : : static void
605 : : pg_attribute_noreturn()
41 drowley@postgresql.o 606 :UNC 0 : SlabAllocInvalidSize(MemoryContext context, Size size)
607 : : {
608 : 0 : SlabContext *slab = (SlabContext *) context;
609 : :
610 [ # # ]: 0 : elog(ERROR, "unexpected alloc chunk size %zu (expected %u)", size,
611 : : slab->chunkSize);
612 : : }
613 : :
614 : : /*
615 : : * SlabAlloc
616 : : * Returns a pointer to a newly allocated memory chunk or raises an ERROR
617 : : * on allocation failure, or returns NULL when flags contains
618 : : * MCXT_ALLOC_NO_OOM. 'size' must be the same size as was specified
619 : : * during SlabContextCreate().
620 : : *
621 : : * This function should only contain the most common code paths. Everything
622 : : * else should be in pg_noinline helper functions, thus avoiding the overhead
623 : : * of creating a stack frame for the common cases. Allocating memory is often
624 : : * a bottleneck in many workloads, so avoiding stack frame setup is
625 : : * worthwhile. Helper functions should always directly return the newly
626 : : * allocated memory so that we can just return that address directly as a tail
627 : : * call.
628 : : */
629 : : void *
47 drowley@postgresql.o 630 :GNC 1846282 : SlabAlloc(MemoryContext context, Size size, int flags)
631 : : {
552 tgl@sss.pgh.pa.us 632 :CBC 1846282 : SlabContext *slab = (SlabContext *) context;
633 : : SlabBlock *block;
634 : : MemoryChunk *chunk;
635 : :
534 peter@eisentraut.org 636 [ + - - + ]: 1846282 : Assert(SlabIsValid(slab));
637 : :
638 : : /* sanity check that this is pointing to a valid blocklist */
481 drowley@postgresql.o 639 [ - + ]: 1846282 : Assert(slab->curBlocklistIndex >= 0);
640 [ - + ]: 1846282 : Assert(slab->curBlocklistIndex <= SlabBlocklistIndex(slab, slab->chunksPerBlock));
641 : :
642 : : /*
643 : : * Make sure we only allow correct request size. This doubles as the
644 : : * MemoryContextCheckSize check.
645 : : */
481 drowley@postgresql.o 646 [ - + ]:GNC 1846282 : if (unlikely(size != slab->chunkSize))
41 drowley@postgresql.o 647 :UNC 0 : SlabAllocInvalidSize(context, size);
648 : :
481 drowley@postgresql.o 649 [ + + ]:CBC 1846282 : if (unlikely(slab->curBlocklistIndex == 0))
650 : : {
651 : : /*
652 : : * Handle the case when there are no partially filled blocks
653 : : * available. This happens either when the last allocation took the
654 : : * last chunk in the block, or when SlabFree() free'd the final block.
655 : : */
41 drowley@postgresql.o 656 :GNC 113877 : return SlabAllocFromNewBlock(context, size, flags);
657 : : }
658 : : else
659 : : {
481 drowley@postgresql.o 660 :CBC 1732405 : dlist_head *blocklist = &slab->blocklist[slab->curBlocklistIndex];
661 : : int new_blocklist_idx;
662 : :
663 [ - + ]: 1732405 : Assert(!dlist_is_empty(blocklist));
664 : :
665 : : /* grab the block from the blocklist */
666 : 1732405 : block = dlist_head_element(SlabBlock, node, blocklist);
667 : :
668 : : /* make sure we actually got a valid block, with matching nfree */
669 [ - + ]: 1732405 : Assert(block != NULL);
670 [ - + ]: 1732405 : Assert(slab->curBlocklistIndex == SlabBlocklistIndex(slab, block->nfree));
671 [ - + ]: 1732405 : Assert(block->nfree > 0);
672 : :
673 : : /* fetch the next chunk from this block */
674 : 1732405 : chunk = SlabGetNextFreeChunk(slab, block);
675 : :
676 : : /* get the new blocklist index based on the new free chunk count */
677 : 1732405 : new_blocklist_idx = SlabBlocklistIndex(slab, block->nfree);
678 : :
679 : : /*
680 : : * Handle the case where the blocklist index changes. This also deals
681 : : * with blocks becoming full as only full blocks go at index 0.
682 : : */
683 [ + + ]: 1732405 : if (unlikely(slab->curBlocklistIndex != new_blocklist_idx))
684 : : {
685 : 47859 : dlist_delete_from(blocklist, &block->node);
686 : 47859 : dlist_push_head(&slab->blocklist[new_blocklist_idx], &block->node);
687 : :
688 [ + + ]: 47859 : if (dlist_is_empty(blocklist))
689 : 46355 : slab->curBlocklistIndex = SlabFindNextBlockListIndex(slab);
690 : : }
691 : : }
692 : :
41 drowley@postgresql.o 693 :GNC 1732405 : return SlabAllocSetupNewChunk(context, block, chunk, size);
694 : : }
695 : :
696 : : /*
697 : : * SlabFree
698 : : * Frees allocated memory; memory is removed from the slab.
699 : : */
700 : : void
594 drowley@postgresql.o 701 :CBC 1761580 : SlabFree(void *pointer)
702 : : {
703 : 1761580 : MemoryChunk *chunk = PointerGetMemoryChunk(pointer);
704 : : SlabBlock *block;
705 : : SlabContext *slab;
706 : : int curBlocklistIdx;
707 : : int newBlocklistIdx;
708 : :
709 : : /* Allow access to the chunk header. */
710 : : VALGRIND_MAKE_MEM_DEFINED(chunk, Slab_CHUNKHDRSZ);
711 : :
365 712 : 1761580 : block = MemoryChunkGetBlock(chunk);
713 : :
714 : : /*
715 : : * For speed reasons we just Assert that the referenced block is good.
716 : : * Future field experience may show that this Assert had better become a
717 : : * regular runtime test-and-elog check.
718 : : */
534 peter@eisentraut.org 719 [ + - + - : 1761580 : Assert(SlabBlockIsValid(block));
- + ]
552 tgl@sss.pgh.pa.us 720 : 1761580 : slab = block->slab;
721 : :
722 : : #ifdef MEMORY_CONTEXT_CHECKING
723 : : /* Test for someone scribbling on unused space in chunk */
585 drowley@postgresql.o 724 [ - + ]: 1761580 : Assert(slab->chunkSize < (slab->fullChunkSize - Slab_CHUNKHDRSZ));
725 [ - + ]: 1761580 : if (!sentinel_ok(pointer, slab->chunkSize))
585 drowley@postgresql.o 726 [ # # ]:UBC 0 : elog(WARNING, "detected write past chunk end in %s %p",
727 : : slab->header.name, chunk);
728 : : #endif
729 : :
730 : : /* push this chunk onto the head of the block's free list */
481 drowley@postgresql.o 731 :CBC 1761580 : *(MemoryChunk **) pointer = block->freehead;
732 : 1761580 : block->freehead = chunk;
733 : :
2603 andres@anarazel.de 734 : 1761580 : block->nfree++;
735 : :
736 [ - + ]: 1761580 : Assert(block->nfree > 0);
737 [ - + ]: 1761580 : Assert(block->nfree <= slab->chunksPerBlock);
738 : :
739 : : #ifdef CLOBBER_FREED_MEMORY
740 : : /* don't wipe the free list MemoryChunk pointer stored in the chunk */
481 drowley@postgresql.o 741 : 1761580 : wipe_mem((char *) pointer + sizeof(MemoryChunk *),
742 : 1761580 : slab->chunkSize - sizeof(MemoryChunk *));
743 : : #endif
744 : :
745 : 1761580 : curBlocklistIdx = SlabBlocklistIndex(slab, block->nfree - 1);
746 : 1761580 : newBlocklistIdx = SlabBlocklistIndex(slab, block->nfree);
747 : :
748 : : /*
749 : : * Check if the block needs to be moved to another element on the
750 : : * blocklist based on it now having 1 more free chunk.
751 : : */
752 [ + + ]: 1761580 : if (unlikely(curBlocklistIdx != newBlocklistIdx))
753 : : {
754 : : /* do the move */
755 : 47853 : dlist_delete_from(&slab->blocklist[curBlocklistIdx], &block->node);
756 : 47853 : dlist_push_head(&slab->blocklist[newBlocklistIdx], &block->node);
757 : :
758 : : /*
759 : : * The blocklist[curBlocklistIdx] may now be empty or we may now be
760 : : * able to use a lower-element blocklist. We'll need to redetermine
761 : : * what the slab->curBlocklistIndex is if the current blocklist was
762 : : * changed or if a lower element one was changed. We must ensure we
763 : : * use the list with the fullest block(s).
764 : : */
479 765 [ + - ]: 47853 : if (slab->curBlocklistIndex >= curBlocklistIdx)
766 : : {
481 767 : 47853 : slab->curBlocklistIndex = SlabFindNextBlockListIndex(slab);
768 : :
769 : : /*
770 : : * We know there must be a block with at least 1 unused chunk as
771 : : * we just pfree'd one. Ensure curBlocklistIndex reflects this.
772 : : */
773 [ - + ]: 47853 : Assert(slab->curBlocklistIndex > 0);
774 : : }
775 : : }
776 : :
777 : : /* Handle when a block becomes completely empty */
778 [ + + ]: 1761580 : if (unlikely(block->nfree == slab->chunksPerBlock))
779 : : {
780 : : /* remove the block */
781 : 29414 : dlist_delete_from(&slab->blocklist[newBlocklistIdx], &block->node);
782 : :
783 : : /*
784 : : * To avoid thrashing malloc/free, we keep a list of empty blocks that
785 : : * we can reuse again instead of having to malloc a new one.
786 : : */
787 [ + + ]: 29414 : if (dclist_count(&slab->emptyblocks) < SLAB_MAXIMUM_EMPTY_BLOCKS)
788 : 27512 : dclist_push_head(&slab->emptyblocks, &block->node);
789 : : else
790 : : {
791 : : /*
792 : : * When we have enough empty blocks stored already, we actually
793 : : * free the block.
794 : : */
795 : : #ifdef CLOBBER_FREED_MEMORY
796 : 1902 : wipe_mem(block, slab->blockSize);
797 : : #endif
798 : 1902 : free(block);
799 : 1902 : slab->header.mem_allocated -= slab->blockSize;
800 : : }
801 : :
802 : : /*
803 : : * Check if we need to reset the blocklist index. This is required
804 : : * when the blocklist this block is on has become completely empty.
805 : : */
806 [ + + + + ]: 41718 : if (slab->curBlocklistIndex == newBlocklistIdx &&
807 : 12304 : dlist_is_empty(&slab->blocklist[newBlocklistIdx]))
808 : 8826 : slab->curBlocklistIndex = SlabFindNextBlockListIndex(slab);
809 : : }
2603 andres@anarazel.de 810 : 1761580 : }
811 : :
812 : : /*
813 : : * SlabRealloc
814 : : * Change the allocated size of a chunk.
815 : : *
816 : : * As Slab is designed for allocating equally-sized chunks of memory, it can't
817 : : * do an actual chunk size change. We try to be gentle and allow calls with
818 : : * exactly the same size, as in that case we can simply return the same
819 : : * chunk. When the size differs, we throw an error.
820 : : *
821 : : * We could also allow requests with size < chunkSize. That however seems
822 : : * rather pointless - Slab is meant for chunks of constant size, and moreover
823 : : * realloc is usually used to enlarge the chunk.
824 : : */
825 : : void *
47 drowley@postgresql.o 826 :UNC 0 : SlabRealloc(void *pointer, Size size, int flags)
827 : : {
594 drowley@postgresql.o 828 :UBC 0 : MemoryChunk *chunk = PointerGetMemoryChunk(pointer);
829 : : SlabBlock *block;
830 : : SlabContext *slab;
831 : :
832 : : /* Allow access to the chunk header. */
833 : : VALGRIND_MAKE_MEM_DEFINED(chunk, Slab_CHUNKHDRSZ);
834 : :
365 835 : 0 : block = MemoryChunkGetBlock(chunk);
836 : :
837 : : /* Disallow access to the chunk header. */
838 : : VALGRIND_MAKE_MEM_NOACCESS(chunk, Slab_CHUNKHDRSZ);
839 : :
840 : : /*
841 : : * Try to verify that we have a sane block pointer: the block header
842 : : * should reference a slab context. (We use a test-and-elog, not just
843 : : * Assert, because it seems highly likely that we're here in error in the
844 : : * first place.)
845 : : */
552 tgl@sss.pgh.pa.us 846 [ # # # # : 0 : if (!SlabBlockIsValid(block))
# # ]
847 [ # # ]: 0 : elog(ERROR, "could not find block containing chunk %p", chunk);
848 : 0 : slab = block->slab;
849 : :
850 : : /* can't do actual realloc with slab, but let's try to be gentle */
2603 andres@anarazel.de 851 [ # # ]: 0 : if (size == slab->chunkSize)
852 : 0 : return pointer;
853 : :
854 [ # # ]: 0 : elog(ERROR, "slab allocator does not support realloc()");
855 : : return NULL; /* keep compiler quiet */
856 : : }
857 : :
858 : : /*
859 : : * SlabGetChunkContext
860 : : * Return the MemoryContext that 'pointer' belongs to.
861 : : */
862 : : MemoryContext
594 drowley@postgresql.o 863 : 0 : SlabGetChunkContext(void *pointer)
864 : : {
865 : 0 : MemoryChunk *chunk = PointerGetMemoryChunk(pointer);
866 : : SlabBlock *block;
867 : :
868 : : /* Allow access to the chunk header. */
869 : : VALGRIND_MAKE_MEM_DEFINED(chunk, Slab_CHUNKHDRSZ);
870 : :
365 871 : 0 : block = MemoryChunkGetBlock(chunk);
872 : :
873 : : /* Disallow access to the chunk header. */
874 : : VALGRIND_MAKE_MEM_NOACCESS(chunk, Slab_CHUNKHDRSZ);
875 : :
534 peter@eisentraut.org 876 [ # # # # : 0 : Assert(SlabBlockIsValid(block));
# # ]
877 : :
552 tgl@sss.pgh.pa.us 878 : 0 : return &block->slab->header;
879 : : }
880 : :
881 : : /*
882 : : * SlabGetChunkSpace
883 : : * Given a currently-allocated chunk, determine the total space
884 : : * it occupies (including all memory-allocation overhead).
885 : : */
886 : : Size
594 drowley@postgresql.o 887 : 0 : SlabGetChunkSpace(void *pointer)
888 : : {
889 : 0 : MemoryChunk *chunk = PointerGetMemoryChunk(pointer);
890 : : SlabBlock *block;
891 : : SlabContext *slab;
892 : :
893 : : /* Allow access to the chunk header. */
894 : : VALGRIND_MAKE_MEM_DEFINED(chunk, Slab_CHUNKHDRSZ);
895 : :
365 896 : 0 : block = MemoryChunkGetBlock(chunk);
897 : :
898 : : /* Disallow access to the chunk header. */
899 : : VALGRIND_MAKE_MEM_NOACCESS(chunk, Slab_CHUNKHDRSZ);
900 : :
534 peter@eisentraut.org 901 [ # # # # : 0 : Assert(SlabBlockIsValid(block));
# # ]
552 tgl@sss.pgh.pa.us 902 : 0 : slab = block->slab;
903 : :
2603 andres@anarazel.de 904 : 0 : return slab->fullChunkSize;
905 : : }
906 : :
907 : : /*
908 : : * SlabIsEmpty
909 : : * Is the slab empty of any allocated space?
910 : : */
911 : : bool
912 : 0 : SlabIsEmpty(MemoryContext context)
913 : : {
481 drowley@postgresql.o 914 [ # # # # ]: 0 : Assert(SlabIsValid((SlabContext *) context));
915 : :
916 : 0 : return (context->mem_allocated == 0);
917 : : }
918 : :
919 : : /*
920 : : * SlabStats
921 : : * Compute stats about memory consumption of a Slab context.
922 : : *
923 : : * printfunc: if not NULL, pass a human-readable stats string to this.
924 : : * passthru: pass this pointer through to printfunc.
925 : : * totals: if not NULL, add stats about this context into *totals.
926 : : * print_to_stderr: print stats to stderr if true, elog otherwise.
927 : : */
928 : : void
2210 tgl@sss.pgh.pa.us 929 : 0 : SlabStats(MemoryContext context,
930 : : MemoryStatsPrintFunc printfunc, void *passthru,
931 : : MemoryContextCounters *totals,
932 : : bool print_to_stderr)
933 : : {
552 934 : 0 : SlabContext *slab = (SlabContext *) context;
2603 andres@anarazel.de 935 : 0 : Size nblocks = 0;
936 : 0 : Size freechunks = 0;
937 : : Size totalspace;
938 : 0 : Size freespace = 0;
939 : : int i;
940 : :
534 peter@eisentraut.org 941 [ # # # # ]: 0 : Assert(SlabIsValid(slab));
942 : :
943 : : /* Include context header in totalspace */
481 drowley@postgresql.o 944 : 0 : totalspace = Slab_CONTEXT_HDRSZ(slab->chunksPerBlock);
945 : :
946 : : /* Add the space consumed by blocks in the emptyblocks list */
947 : 0 : totalspace += dclist_count(&slab->emptyblocks) * slab->blockSize;
948 : :
949 [ # # ]: 0 : for (i = 0; i < SLAB_BLOCKLIST_COUNT; i++)
950 : : {
951 : : dlist_iter iter;
952 : :
953 [ # # # # ]: 0 : dlist_foreach(iter, &slab->blocklist[i])
954 : : {
2603 andres@anarazel.de 955 : 0 : SlabBlock *block = dlist_container(SlabBlock, node, iter.cur);
956 : :
957 : 0 : nblocks++;
958 : 0 : totalspace += slab->blockSize;
959 : 0 : freespace += slab->fullChunkSize * block->nfree;
960 : 0 : freechunks += block->nfree;
961 : : }
962 : : }
963 : :
2210 tgl@sss.pgh.pa.us 964 [ # # ]: 0 : if (printfunc)
965 : : {
966 : : char stats_string[200];
967 : :
968 : : /* XXX should we include free chunks on empty blocks? */
969 : 0 : snprintf(stats_string, sizeof(stats_string),
970 : : "%zu total in %zu blocks; %u empty blocks; %zu free (%zu chunks); %zu used",
481 drowley@postgresql.o 971 : 0 : totalspace, nblocks, dclist_count(&slab->emptyblocks),
972 : : freespace, freechunks, totalspace - freespace);
1104 fujii@postgresql.org 973 : 0 : printfunc(context, passthru, stats_string, print_to_stderr);
974 : : }
975 : :
2603 andres@anarazel.de 976 [ # # ]: 0 : if (totals)
977 : : {
978 : 0 : totals->nblocks += nblocks;
979 : 0 : totals->freechunks += freechunks;
980 : 0 : totals->totalspace += totalspace;
981 : 0 : totals->freespace += freespace;
982 : : }
983 : 0 : }
984 : :
985 : :
986 : : #ifdef MEMORY_CONTEXT_CHECKING
987 : :
988 : : /*
989 : : * SlabCheck
990 : : * Walk through all blocks looking for inconsistencies.
991 : : *
992 : : * NOTE: report errors as WARNING, *not* ERROR or FATAL. Otherwise you'll
993 : : * find yourself in an infinite loop when trouble occurs, because this
994 : : * routine will be entered again when elog cleanup tries to release memory!
995 : : */
996 : : void
2603 andres@anarazel.de 997 :CBC 423455 : SlabCheck(MemoryContext context)
998 : : {
552 tgl@sss.pgh.pa.us 999 : 423455 : SlabContext *slab = (SlabContext *) context;
1000 : : int i;
481 drowley@postgresql.o 1001 : 423455 : int nblocks = 0;
2314 tgl@sss.pgh.pa.us 1002 : 423455 : const char *name = slab->header.name;
1003 : : dlist_iter iter;
1004 : :
534 peter@eisentraut.org 1005 [ + - - + ]: 423455 : Assert(SlabIsValid(slab));
2603 andres@anarazel.de 1006 [ - + ]: 423455 : Assert(slab->chunksPerBlock > 0);
1007 : :
1008 : : /*
1009 : : * Have a look at the empty blocks. These should have all their chunks
1010 : : * marked as free. Ensure that's the case.
1011 : : */
481 drowley@postgresql.o 1012 [ + - + + ]: 424806 : dclist_foreach(iter, &slab->emptyblocks)
1013 : : {
1014 : 1351 : SlabBlock *block = dlist_container(SlabBlock, node, iter.cur);
1015 : :
1016 [ - + ]: 1351 : if (block->nfree != slab->chunksPerBlock)
481 drowley@postgresql.o 1017 [ # # ]:UBC 0 : elog(WARNING, "problem in slab %s: empty block %p should have %d free chunks but has %d chunks free",
1018 : : name, block, slab->chunksPerBlock, block->nfree);
1019 : : }
1020 : :
1021 : : /* walk the non-empty block lists */
481 drowley@postgresql.o 1022 [ + + ]:CBC 1693820 : for (i = 0; i < SLAB_BLOCKLIST_COUNT; i++)
1023 : : {
1024 : : int j,
1025 : : nfree;
1026 : :
1027 : : /* walk all blocks on this blocklist */
1028 [ + - + + ]: 1354826 : dlist_foreach(iter, &slab->blocklist[i])
1029 : : {
2603 andres@anarazel.de 1030 : 84461 : SlabBlock *block = dlist_container(SlabBlock, node, iter.cur);
1031 : : MemoryChunk *cur_chunk;
1032 : :
1033 : : /*
1034 : : * Make sure the number of free chunks (in the block header)
1035 : : * matches the position in the blocklist.
1036 : : */
481 drowley@postgresql.o 1037 [ - + ]: 84461 : if (SlabBlocklistIndex(slab, block->nfree) != i)
481 drowley@postgresql.o 1038 [ # # ]:UBC 0 : elog(WARNING, "problem in slab %s: block %p is on blocklist %d but should be on blocklist %d",
1039 : : name, block, i, SlabBlocklistIndex(slab, block->nfree));
1040 : :
1041 : : /* make sure the block is not empty */
481 drowley@postgresql.o 1042 [ - + ]:CBC 84461 : if (block->nfree >= slab->chunksPerBlock)
481 drowley@postgresql.o 1043 [ # # ]:UBC 0 : elog(WARNING, "problem in slab %s: empty block %p incorrectly stored on blocklist element %d",
1044 : : name, block, i);
1045 : :
1046 : : /* make sure the slab pointer correctly points to this context */
594 drowley@postgresql.o 1047 [ - + ]:CBC 84461 : if (block->slab != slab)
594 drowley@postgresql.o 1048 [ # # ]:UBC 0 : elog(WARNING, "problem in slab %s: bogus slab link in block %p",
1049 : : name, block);
1050 : :
1051 : : /* reset the array of free chunks for this block */
481 drowley@postgresql.o 1052 :CBC 84461 : memset(slab->isChunkFree, 0, (slab->chunksPerBlock * sizeof(bool)));
1053 : 84461 : nfree = 0;
1054 : :
1055 : : /* walk through the block's free list chunks */
1056 : 84461 : cur_chunk = block->freehead;
1057 [ + + ]: 86407 : while (cur_chunk != NULL)
1058 : : {
1059 : 1946 : int chunkidx = SlabChunkIndex(slab, block, cur_chunk);
1060 : :
1061 : : /*
1062 : : * Ensure the free list link points to something on the block
1063 : : * at an address aligned according to the full chunk size.
1064 : : */
1065 [ + - ]: 1946 : if (cur_chunk < SlabBlockGetChunk(slab, block, 0) ||
1066 [ + - ]: 1946 : cur_chunk > SlabBlockGetChunk(slab, block, slab->chunksPerBlock - 1) ||
1067 [ - + ]: 1946 : SlabChunkMod(slab, block, cur_chunk) != 0)
481 drowley@postgresql.o 1068 [ # # ]:UBC 0 : elog(WARNING, "problem in slab %s: bogus free list link %p in block %p",
1069 : : name, cur_chunk, block);
1070 : :
1071 : : /* count the chunk and mark it free on the free chunk array */
481 drowley@postgresql.o 1072 :CBC 1946 : nfree++;
1073 : 1946 : slab->isChunkFree[chunkidx] = true;
1074 : :
1075 : : /* read pointer of the next free chunk */
1076 : : VALGRIND_MAKE_MEM_DEFINED(MemoryChunkGetPointer(cur_chunk), sizeof(MemoryChunk *));
1077 : 1946 : cur_chunk = *(MemoryChunk **) SlabChunkGetPointer(cur_chunk);
1078 : : }
1079 : :
1080 : : /* check that the unused pointer matches what nunused claims */
1081 : 84461 : if (SlabBlockGetChunk(slab, block, slab->chunksPerBlock - block->nunused) !=
1082 [ - + ]: 84461 : block->unused)
481 drowley@postgresql.o 1083 [ # # ]:UBC 0 : elog(WARNING, "problem in slab %s: mismatch detected between nunused chunks and unused pointer in block %p",
1084 : : name, block);
1085 : :
1086 : : /*
1087 : : * count the remaining free chunks that have yet to make it onto
1088 : : * the block's free list.
1089 : : */
481 drowley@postgresql.o 1090 :CBC 84461 : cur_chunk = block->unused;
1091 [ + + ]: 10700889 : for (j = 0; j < block->nunused; j++)
1092 : : {
1093 : 10616428 : int chunkidx = SlabChunkIndex(slab, block, cur_chunk);
1094 : :
1095 : :
1096 : : /* count the chunk as free and mark it as so in the array */
2603 andres@anarazel.de 1097 : 10616428 : nfree++;
481 drowley@postgresql.o 1098 [ + - ]: 10616428 : if (chunkidx < slab->chunksPerBlock)
1099 : 10616428 : slab->isChunkFree[chunkidx] = true;
1100 : :
1101 : : /* move forward 1 chunk */
1102 : 10616428 : cur_chunk = (MemoryChunk *) (((char *) cur_chunk) + slab->fullChunkSize);
1103 : : }
1104 : :
2603 andres@anarazel.de 1105 [ + + ]: 10787599 : for (j = 0; j < slab->chunksPerBlock; j++)
1106 : : {
481 drowley@postgresql.o 1107 [ + + ]: 10703138 : if (!slab->isChunkFree[j])
1108 : : {
594 1109 : 84764 : MemoryChunk *chunk = SlabBlockGetChunk(slab, block, j);
1110 : : SlabBlock *chunkblock;
1111 : :
1112 : : /* Allow access to the chunk header. */
1113 : : VALGRIND_MAKE_MEM_DEFINED(chunk, Slab_CHUNKHDRSZ);
1114 : :
365 1115 : 84764 : chunkblock = (SlabBlock *) MemoryChunkGetBlock(chunk);
1116 : :
1117 : : /* Disallow access to the chunk header. */
1118 : : VALGRIND_MAKE_MEM_NOACCESS(chunk, Slab_CHUNKHDRSZ);
1119 : :
1120 : : /*
1121 : : * check the chunk's blockoffset correctly points back to
1122 : : * the block
1123 : : */
594 1124 [ - + ]: 84764 : if (chunkblock != block)
2603 andres@anarazel.de 1125 [ # # ]:UBC 0 : elog(WARNING, "problem in slab %s: bogus block link in block %p, chunk %p",
1126 : : name, block, chunk);
1127 : :
1128 : : /* check the sentinel byte is intact */
585 drowley@postgresql.o 1129 [ - + ]:CBC 84764 : Assert(slab->chunkSize < (slab->fullChunkSize - Slab_CHUNKHDRSZ));
1130 [ - + ]: 84764 : if (!sentinel_ok(chunk, Slab_CHUNKHDRSZ + slab->chunkSize))
585 drowley@postgresql.o 1131 [ # # ]:UBC 0 : elog(WARNING, "problem in slab %s: detected write past chunk end in block %p, chunk %p",
1132 : : name, block, chunk);
1133 : : }
1134 : : }
1135 : :
1136 : : /*
1137 : : * Make sure we got the expected number of free chunks (as tracked
1138 : : * in the block header).
1139 : : */
2603 andres@anarazel.de 1140 [ - + ]:CBC 84461 : if (nfree != block->nfree)
481 drowley@postgresql.o 1141 [ # # ]:UBC 0 : elog(WARNING, "problem in slab %s: nfree in block %p is %d but %d chunk were found as free",
1142 : : name, block, block->nfree, nfree);
1143 : :
481 drowley@postgresql.o 1144 :CBC 84461 : nblocks++;
1145 : : }
1146 : : }
1147 : :
1148 : : /* the stored empty blocks are tracked in mem_allocated too */
1149 : 423455 : nblocks += dclist_count(&slab->emptyblocks);
1150 : :
1151 [ - + ]: 423455 : Assert(nblocks * slab->blockSize == context->mem_allocated);
2603 andres@anarazel.de 1152 : 423455 : }
1153 : :
1154 : : #endif /* MEMORY_CONTEXT_CHECKING */
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