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) 2001-2022, 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 statistics
      28             :  */
      29             : void
      30       10478 : pgstat_report_bgwriter(void)
      31             : {
      32       10478 :     PgStatShared_BgWriter *stats_shmem = &pgStatLocal.shmem->bgwriter;
      33             :     static const PgStat_BgWriterStats all_zeroes;
      34             : 
      35             :     Assert(!pgStatLocal.shmem->is_shutdown);
      36             :     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       10478 :     if (memcmp(&PendingBgWriterStats, &all_zeroes, sizeof(all_zeroes)) == 0)
      43        3970 :         return;
      44             : 
      45        6508 :     pgstat_begin_changecount_write(&stats_shmem->changecount);
      46             : 
      47             : #define BGWRITER_ACC(fld) stats_shmem->stats.fld += PendingBgWriterStats.fld
      48        6508 :     BGWRITER_ACC(buf_written_clean);
      49        6508 :     BGWRITER_ACC(maxwritten_clean);
      50        6508 :     BGWRITER_ACC(buf_alloc);
      51             : #undef BGWRITER_ACC
      52             : 
      53        6508 :     pgstat_end_changecount_write(&stats_shmem->changecount);
      54             : 
      55             :     /*
      56             :      * Clear out the statistics buffer, so it can be re-used.
      57             :      */
      58       32540 :     MemSet(&PendingBgWriterStats, 0, sizeof(PendingBgWriterStats));
      59             : }
      60             : 
      61             : /*
      62             :  * Support function for the SQL-callable pgstat* functions. Returns
      63             :  * a pointer to the bgwriter statistics struct.
      64             :  */
      65             : PgStat_BgWriterStats *
      66          32 : pgstat_fetch_stat_bgwriter(void)
      67             : {
      68          32 :     pgstat_snapshot_fixed(PGSTAT_KIND_BGWRITER);
      69             : 
      70          32 :     return &pgStatLocal.snapshot.bgwriter;
      71             : }
      72             : 
      73             : void
      74         818 : pgstat_bgwriter_reset_all_cb(TimestampTz ts)
      75             : {
      76         818 :     PgStatShared_BgWriter *stats_shmem = &pgStatLocal.shmem->bgwriter;
      77             : 
      78             :     /* see explanation above PgStatShared_BgWriter for the reset protocol */
      79         818 :     LWLockAcquire(&stats_shmem->lock, LW_EXCLUSIVE);
      80         818 :     pgstat_copy_changecounted_stats(&stats_shmem->reset_offset,
      81         818 :                                     &stats_shmem->stats,
      82             :                                     sizeof(stats_shmem->stats),
      83             :                                     &stats_shmem->changecount);
      84         818 :     stats_shmem->stats.stat_reset_timestamp = ts;
      85         818 :     LWLockRelease(&stats_shmem->lock);
      86         818 : }
      87             : 
      88             : void
      89        1842 : pgstat_bgwriter_snapshot_cb(void)
      90             : {
      91        1842 :     PgStatShared_BgWriter *stats_shmem = &pgStatLocal.shmem->bgwriter;
      92        1842 :     PgStat_BgWriterStats *reset_offset = &stats_shmem->reset_offset;
      93             :     PgStat_BgWriterStats reset;
      94             : 
      95        1842 :     pgstat_copy_changecounted_stats(&pgStatLocal.snapshot.bgwriter,
      96        1842 :                                     &stats_shmem->stats,
      97             :                                     sizeof(stats_shmem->stats),
      98             :                                     &stats_shmem->changecount);
      99             : 
     100        1842 :     LWLockAcquire(&stats_shmem->lock, LW_SHARED);
     101        1842 :     memcpy(&reset, reset_offset, sizeof(stats_shmem->stats));
     102        1842 :     LWLockRelease(&stats_shmem->lock);
     103             : 
     104             :     /* compensate by reset offsets */
     105             : #define BGWRITER_COMP(fld) pgStatLocal.snapshot.bgwriter.fld -= reset.fld;
     106        1842 :     BGWRITER_COMP(buf_written_clean);
     107        1842 :     BGWRITER_COMP(maxwritten_clean);
     108        1842 :     BGWRITER_COMP(buf_alloc);
     109             : #undef BGWRITER_COMP
     110        1842 : }