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/* -------------------------------------------------------------------------
*
* pgstat_bgwriter.c
* Implementation of bgwriter statistics.
*
* This file contains the implementation of bgwriter statistics. It is kept
* separate from pgstat.c to enforce the line between the statistics access /
* storage implementation and the details about individual types of
* statistics.
*
* Copyright (c) 2001-2023, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/backend/utils/activity/pgstat_bgwriter.c
* -------------------------------------------------------------------------
*/
#include "postgres.h"
#include "utils/pgstat_internal.h"
PgStat_BgWriterStats PendingBgWriterStats = {0};
/*
* Report bgwriter and IO statistics
*/
void
pgstat_report_bgwriter(void)
{
PgStatShared_BgWriter *stats_shmem = &pgStatLocal.shmem->bgwriter;
static const PgStat_BgWriterStats all_zeroes;
Assert(!pgStatLocal.shmem->is_shutdown);
pgstat_assert_is_up();
/*
* This function can be called even if nothing at all has happened. In
* this case, avoid unnecessarily modifying the stats entry.
*/
if (memcmp(&PendingBgWriterStats, &all_zeroes, sizeof(all_zeroes)) == 0)
return;
pgstat_begin_changecount_write(&stats_shmem->changecount);
#define BGWRITER_ACC(fld) stats_shmem->stats.fld += PendingBgWriterStats.fld
BGWRITER_ACC(buf_written_clean);
BGWRITER_ACC(maxwritten_clean);
BGWRITER_ACC(buf_alloc);
#undef BGWRITER_ACC
pgstat_end_changecount_write(&stats_shmem->changecount);
/*
* Clear out the statistics buffer, so it can be re-used.
*/
MemSet(&PendingBgWriterStats, 0, sizeof(PendingBgWriterStats));
/*
* Report IO statistics
*/
pgstat_flush_io(false);
}
/*
* Support function for the SQL-callable pgstat* functions. Returns
* a pointer to the bgwriter statistics struct.
*/
PgStat_BgWriterStats *
pgstat_fetch_stat_bgwriter(void)
{
pgstat_snapshot_fixed(PGSTAT_KIND_BGWRITER);
return &pgStatLocal.snapshot.bgwriter;
}
void
pgstat_bgwriter_reset_all_cb(TimestampTz ts)
{
PgStatShared_BgWriter *stats_shmem = &pgStatLocal.shmem->bgwriter;
/* see explanation above PgStatShared_BgWriter for the reset protocol */
LWLockAcquire(&stats_shmem->lock, LW_EXCLUSIVE);
pgstat_copy_changecounted_stats(&stats_shmem->reset_offset,
&stats_shmem->stats,
sizeof(stats_shmem->stats),
&stats_shmem->changecount);
stats_shmem->stats.stat_reset_timestamp = ts;
LWLockRelease(&stats_shmem->lock);
}
void
pgstat_bgwriter_snapshot_cb(void)
{
PgStatShared_BgWriter *stats_shmem = &pgStatLocal.shmem->bgwriter;
PgStat_BgWriterStats *reset_offset = &stats_shmem->reset_offset;
PgStat_BgWriterStats reset;
pgstat_copy_changecounted_stats(&pgStatLocal.snapshot.bgwriter,
&stats_shmem->stats,
sizeof(stats_shmem->stats),
&stats_shmem->changecount);
LWLockAcquire(&stats_shmem->lock, LW_SHARED);
memcpy(&reset, reset_offset, sizeof(stats_shmem->stats));
LWLockRelease(&stats_shmem->lock);
/* compensate by reset offsets */
#define BGWRITER_COMP(fld) pgStatLocal.snapshot.bgwriter.fld -= reset.fld;
BGWRITER_COMP(buf_written_clean);
BGWRITER_COMP(maxwritten_clean);
BGWRITER_COMP(buf_alloc);
#undef BGWRITER_COMP
}
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