TLA  Line data    Source code

       1                 : /* -------------------------------------------------------------------------
       2                 :  *
       3                 :  * pgstat_bgwriter.c
       4                 :  *    Implementation of bgwriter statistics.
       5                 :  *
       6                 :  * This file contains the implementation of bgwriter statistics. It is kept
       7                 :  * separate from pgstat.c to enforce the line between the statistics access /
       8                 :  * storage implementation and the details about individual types of
       9                 :  * statistics.
      10                 :  *
      11                 :  * Copyright (c) 2001-2023, PostgreSQL Global Development Group
      12                 :  *
      13                 :  * IDENTIFICATION
      14                 :  *    src/backend/utils/activity/pgstat_bgwriter.c
      15                 :  * -------------------------------------------------------------------------
      16                 :  */
      17                 : 
      18                 : #include "postgres.h"
      19                 : 
      20                 : #include "utils/pgstat_internal.h"
      21                 : 
      22                 : 
      23                 : PgStat_BgWriterStats PendingBgWriterStats = {0};
      24                 : 
      25                 : 
      26                 : /*
      27                 :  * Report bgwriter and IO statistics
      28                 :  */
      29                 : void
      30 CBC       10438 : pgstat_report_bgwriter(void)
      31                 : {
      32           10438 :     PgStatShared_BgWriter *stats_shmem = &pgStatLocal.shmem->bgwriter;
      33                 :     static const PgStat_BgWriterStats all_zeroes;
      34                 : 
      35           10438 :     Assert(!pgStatLocal.shmem->is_shutdown);
      36           10438 :     pgstat_assert_is_up();
      37                 : 
      38                 :     /*
      39                 :      * This function can be called even if nothing at all has happened. In
      40                 :      * this case, avoid unnecessarily modifying the stats entry.
      41                 :      */
      42           10438 :     if (memcmp(&PendingBgWriterStats, &all_zeroes, sizeof(all_zeroes)) == 0)
      43            4850 :         return;
      44                 : 
      45            5588 :     pgstat_begin_changecount_write(&stats_shmem->changecount);
      46                 : 
      47                 : #define BGWRITER_ACC(fld) stats_shmem->stats.fld += PendingBgWriterStats.fld
      48            5588 :     BGWRITER_ACC(buf_written_clean);
      49            5588 :     BGWRITER_ACC(maxwritten_clean);
      50            5588 :     BGWRITER_ACC(buf_alloc);
      51                 : #undef BGWRITER_ACC
      52                 : 
      53            5588 :     pgstat_end_changecount_write(&stats_shmem->changecount);
      54                 : 
      55                 :     /*
      56                 :      * Clear out the statistics buffer, so it can be re-used.
      57                 :      */
      58           27940 :     MemSet(&PendingBgWriterStats, 0, sizeof(PendingBgWriterStats));
      59                 : 
      60                 :     /*
      61                 :      * Report IO statistics
      62                 :      */
      63 GNC        5588 :     pgstat_flush_io(false);
      64                 : }
      65                 : 
      66                 : /*
      67                 :  * Support function for the SQL-callable pgstat* functions. Returns
      68 ECB             :  * a pointer to the bgwriter statistics struct.
      69                 :  */
      70                 : PgStat_BgWriterStats *
      71 GIC          16 : pgstat_fetch_stat_bgwriter(void)
      72                 : {
      73              16 :     pgstat_snapshot_fixed(PGSTAT_KIND_BGWRITER);
      74                 : 
      75              16 :     return &pgStatLocal.snapshot.bgwriter;
      76 ECB             : }
      77                 : 
      78                 : void
      79 GIC         442 : pgstat_bgwriter_reset_all_cb(TimestampTz ts)
      80 ECB             : {
      81 GIC         442 :     PgStatShared_BgWriter *stats_shmem = &pgStatLocal.shmem->bgwriter;
      82                 : 
      83                 :     /* see explanation above PgStatShared_BgWriter for the reset protocol */
      84 CBC         442 :     LWLockAcquire(&stats_shmem->lock, LW_EXCLUSIVE);
      85 GIC         442 :     pgstat_copy_changecounted_stats(&stats_shmem->reset_offset,
      86 CBC         442 :                                     &stats_shmem->stats,
      87                 :                                     sizeof(stats_shmem->stats),
      88                 :                                     &stats_shmem->changecount);
      89             442 :     stats_shmem->stats.stat_reset_timestamp = ts;
      90             442 :     LWLockRelease(&stats_shmem->lock);
      91             442 : }
      92                 : 
      93                 : void
      94            1008 : pgstat_bgwriter_snapshot_cb(void)
      95 ECB             : {
      96 CBC        1008 :     PgStatShared_BgWriter *stats_shmem = &pgStatLocal.shmem->bgwriter;
      97 GIC        1008 :     PgStat_BgWriterStats *reset_offset = &stats_shmem->reset_offset;
      98                 :     PgStat_BgWriterStats reset;
      99 ECB             : 
     100 GIC        1008 :     pgstat_copy_changecounted_stats(&pgStatLocal.snapshot.bgwriter,
     101 CBC        1008 :                                     &stats_shmem->stats,
     102 ECB             :                                     sizeof(stats_shmem->stats),
     103                 :                                     &stats_shmem->changecount);
     104                 : 
     105 CBC        1008 :     LWLockAcquire(&stats_shmem->lock, LW_SHARED);
     106            1008 :     memcpy(&reset, reset_offset, sizeof(stats_shmem->stats));
     107 GIC        1008 :     LWLockRelease(&stats_shmem->lock);
     108                 : 
     109                 :     /* compensate by reset offsets */
     110 ECB             : #define BGWRITER_COMP(fld) pgStatLocal.snapshot.bgwriter.fld -= reset.fld;
     111 CBC        1008 :     BGWRITER_COMP(buf_written_clean);
     112            1008 :     BGWRITER_COMP(maxwritten_clean);
     113 GIC        1008 :     BGWRITER_COMP(buf_alloc);
     114                 : #undef BGWRITER_COMP
     115            1008 : }