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Previously the statistics collector received statistics updates via UDP and shared statistics data by writing them out to temporary files regularly. These files can reach tens of megabytes and are written out up to twice a second. This has repeatedly prevented us from adding additional useful statistics. Now statistics are stored in shared memory. Statistics for variable-numbered objects are stored in a dshash hashtable (backed by dynamic shared memory). Fixed-numbered stats are stored in plain shared memory. The header for pgstat.c contains an overview of the architecture. The stats collector is not needed anymore, remove it. By utilizing the transactional statistics drop infrastructure introduced in a prior commit statistics entries cannot "leak" anymore. Previously leaked statistics were dropped by pgstat_vacuum_stat(), called from [auto-]vacuum. On systems with many small relations pgstat_vacuum_stat() could be quite expensive. Now that replicas drop statistics entries for dropped objects, it is not necessary anymore to reset stats when starting from a cleanly shut down replica. Subsequent commits will perform some further code cleanup, adapt docs and add tests. Bumps PGSTAT_FILE_FORMAT_ID. Author: Kyotaro Horiguchi <horikyota.ntt@gmail.com> Author: Andres Freund <andres@anarazel.de> Author: Melanie Plageman <melanieplageman@gmail.com> Reviewed-By: Andres Freund <andres@anarazel.de> Reviewed-By: Thomas Munro <thomas.munro@gmail.com> Reviewed-By: Justin Pryzby <pryzby@telsasoft.com> Reviewed-By: "David G. Johnston" <david.g.johnston@gmail.com> Reviewed-By: Tomas Vondra <tomas.vondra@2ndquadrant.com> (in a much earlier version) Reviewed-By: Arthur Zakirov <a.zakirov@postgrespro.ru> (in a much earlier version) Reviewed-By: Antonin Houska <ah@cybertec.at> (in a much earlier version) Discussion: https://postgr.es/m/20220303021600.hs34ghqcw6zcokdh@alap3.anarazel.de Discussion: https://postgr.es/m/20220308205351.2xcn6k4x5yivcxyd@alap3.anarazel.de Discussion: https://postgr.es/m/20210319235115.y3wz7hpnnrshdyv6@alap3.anarazel.de
111 lines
3.1 KiB
C
111 lines
3.1 KiB
C
/* -------------------------------------------------------------------------
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*
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* pgstat_bgwriter.c
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* Implementation of bgwriter statistics.
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*
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* This file contains the implementation of bgwriter statistics. It is kept
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* separate from pgstat.c to enforce the line between the statistics access /
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* storage implementation and the details about individual types of
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* statistics.
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*
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* Copyright (c) 2001-2022, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* src/backend/utils/activity/pgstat_bgwriter.c
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* -------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "utils/pgstat_internal.h"
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PgStat_BgWriterStats PendingBgWriterStats = {0};
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/*
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* Report bgwriter statistics
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*/
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void
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pgstat_report_bgwriter(void)
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{
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PgStatShared_BgWriter *stats_shmem = &pgStatLocal.shmem->bgwriter;
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static const PgStat_BgWriterStats all_zeroes;
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Assert(!pgStatLocal.shmem->is_shutdown);
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pgstat_assert_is_up();
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/*
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* This function can be called even if nothing at all has happened. In
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* this case, avoid unnecessarily modifying the stats entry.
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*/
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if (memcmp(&PendingBgWriterStats, &all_zeroes, sizeof(all_zeroes)) == 0)
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return;
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pgstat_begin_changecount_write(&stats_shmem->changecount);
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#define BGWRITER_ACC(fld) stats_shmem->stats.fld += PendingBgWriterStats.fld
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BGWRITER_ACC(buf_written_clean);
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BGWRITER_ACC(maxwritten_clean);
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BGWRITER_ACC(buf_alloc);
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#undef BGWRITER_ACC
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pgstat_end_changecount_write(&stats_shmem->changecount);
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/*
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* Clear out the statistics buffer, so it can be re-used.
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*/
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MemSet(&PendingBgWriterStats, 0, sizeof(PendingBgWriterStats));
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}
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/*
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* Support function for the SQL-callable pgstat* functions. Returns
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* a pointer to the bgwriter statistics struct.
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*/
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PgStat_BgWriterStats *
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pgstat_fetch_stat_bgwriter(void)
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{
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pgstat_snapshot_fixed(PGSTAT_KIND_BGWRITER);
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return &pgStatLocal.snapshot.bgwriter;
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}
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void
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pgstat_bgwriter_reset_all_cb(TimestampTz ts)
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{
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PgStatShared_BgWriter *stats_shmem = &pgStatLocal.shmem->bgwriter;
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/* see explanation above PgStatShared_BgWriter for the reset protocol */
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LWLockAcquire(&stats_shmem->lock, LW_EXCLUSIVE);
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pgstat_copy_changecounted_stats(&stats_shmem->reset_offset,
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&stats_shmem->stats,
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sizeof(stats_shmem->stats),
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&stats_shmem->changecount);
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stats_shmem->stats.stat_reset_timestamp = ts;
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LWLockRelease(&stats_shmem->lock);
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}
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void
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pgstat_bgwriter_snapshot_cb(void)
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{
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PgStatShared_BgWriter *stats_shmem = &pgStatLocal.shmem->bgwriter;
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PgStat_BgWriterStats *reset_offset = &stats_shmem->reset_offset;
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PgStat_BgWriterStats reset;
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pgstat_copy_changecounted_stats(&pgStatLocal.snapshot.bgwriter,
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&stats_shmem->stats,
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sizeof(stats_shmem->stats),
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&stats_shmem->changecount);
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LWLockAcquire(&stats_shmem->lock, LW_SHARED);
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memcpy(&reset, reset_offset, sizeof(stats_shmem->stats));
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LWLockRelease(&stats_shmem->lock);
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/* compensate by reset offsets */
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#define BGWRITER_COMP(fld) pgStatLocal.snapshot.bgwriter.fld -= reset.fld;
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BGWRITER_COMP(buf_written_clean);
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BGWRITER_COMP(maxwritten_clean);
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BGWRITER_COMP(buf_alloc);
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#undef BGWRITER_COMP
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}
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