From 88cf6d9237f98b55d75947700d541afaeb7ee4ca Mon Sep 17 00:00:00 2001 From: Melanie Plageman Date: Mon, 20 Dec 2021 16:48:06 -0500 Subject: [PATCH v19 9/9] Add stats to pg_stat_bgwriter Rename pg_stat_bgwriter stat "maxwritten_clean" to "rounds_hit_limit". This stat tracks the number of rounds in which the bgwriter hit the limit imposed by bgwriter_lru_maxpages for the number of pages which are allowed to be cleaned in a round. Also, add two new additional stats to this view. The first, "rounds_cleaned_estimate", is the number of rounds in which the bgwriter was able to clean the number of buffers which it has estimated will be allocated in the next cycle. The second, "rounds_lapped_clock", is the number of rounds in which the bgwriter lapped the freelist clock sweep scan. Both of these are conditions to exit the LRU cleaning scan. --- doc/src/sgml/monitoring.sgml | 22 +++++++++++++++++++++- src/backend/catalog/system_views.sql | 4 +++- src/backend/postmaster/pgstat.c | 5 ++++- src/backend/storage/buffer/bufmgr.c | 21 +++++++++++++++------ src/backend/utils/adt/pgstatfuncs.c | 16 ++++++++++++++-- src/include/catalog/pg_proc.dat | 15 +++++++++++++-- src/include/pgstat.h | 8 ++++++-- src/test/regress/expected/rules.out | 4 +++- 8 files changed, 79 insertions(+), 16 deletions(-) diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml index 84c37151b8..e029a596c9 100644 --- a/doc/src/sgml/monitoring.sgml +++ b/doc/src/sgml/monitoring.sgml @@ -3523,7 +3523,17 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i - maxwritten_clean bigint + rounds_cleaned_estimate bigint + + + Number of rounds in which the bgwriter cleaned the number of buffers it + estimated would be allocated in the next cycle. + + + + + + rounds_hit_limit bigint Number of times the background writer stopped a cleaning @@ -3531,6 +3541,16 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i + + + rounds_lapped_clock bigint + + + Number of rounds in which the bgwriter lapped the clock sweep scan while + cleaning buffers. + + + stats_reset timestamp with time zone diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql index 0caf50421c..8ac1988d21 100644 --- a/src/backend/catalog/system_views.sql +++ b/src/backend/catalog/system_views.sql @@ -1064,7 +1064,9 @@ CREATE VIEW pg_stat_archiver AS CREATE VIEW pg_stat_bgwriter AS SELECT - pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean, + pg_stat_get_bgwriter_rounds_cleaned_estimate() AS rounds_cleaned_estimate, + pg_stat_get_bgwriter_rounds_hit_limit() AS rounds_hit_limit, + pg_stat_get_bgwriter_rounds_lapped_clock() AS rounds_lapped_clock, pg_stat_get_bgwriter_stat_reset_time() AS stats_reset; CREATE VIEW pg_stat_buffers AS diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c index a080ec78b4..a441216d25 100644 --- a/src/backend/postmaster/pgstat.c +++ b/src/backend/postmaster/pgstat.c @@ -5951,7 +5951,10 @@ pgstat_recv_archiver(PgStat_MsgArchiver *msg, int len) static void pgstat_recv_bgwriter(PgStat_MsgBgWriter *msg, int len) { - globalStats.bgwriter.maxwritten_clean += msg->m_maxwritten_clean; + globalStats.bgwriter.rounds_cleaned_estimate += + msg->m_rounds_cleaned_estimate; + globalStats.bgwriter.rounds_hit_limit += msg->m_rounds_hit_limit; + globalStats.bgwriter.rounds_lapped_clock += msg->m_rounds_lapped_clock; } /* ---------- diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c index 6ec15ea00e..5830b971d6 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -2454,20 +2454,29 @@ BgBufferSync(WritebackContext *wb_context) next_to_clean = 0; next_passes++; } - num_to_scan--; - if (sync_state & BUF_WRITTEN) + if (--num_to_scan == 0) + PendingBgWriterStats.m_rounds_lapped_clock++; + + if (sync_state & BUF_WRITTEN || sync_state & BUF_REUSABLE) { reusable_buffers++; - if (++num_written >= bgwriter_lru_maxpages) + if (reusable_buffers >= upcoming_alloc_est) + PendingBgWriterStats.m_rounds_cleaned_estimate++; + } + + if (sync_state & BUF_WRITTEN) + { + num_written++; + if (num_written >= bgwriter_lru_maxpages) { - PendingBgWriterStats.m_maxwritten_clean++; + PendingBgWriterStats.m_rounds_hit_limit++; break; } } - else if (sync_state & BUF_REUSABLE) - reusable_buffers++; + } + #ifdef BGW_DEBUG elog(DEBUG1, "bgwriter: recent_alloc=%u smoothed=%.2f delta=%ld ahead=%d density=%.2f reusable_est=%d upcoming_est=%d scanned=%d wrote=%d reusable=%d", diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c index 6ee9705ea3..eafcaf4abf 100644 --- a/src/backend/utils/adt/pgstatfuncs.c +++ b/src/backend/utils/adt/pgstatfuncs.c @@ -1727,9 +1727,21 @@ pg_stat_get_db_sessions_killed(PG_FUNCTION_ARGS) } Datum -pg_stat_get_bgwriter_maxwritten_clean(PG_FUNCTION_ARGS) +pg_stat_get_bgwriter_rounds_cleaned_estimate(PG_FUNCTION_ARGS) { - PG_RETURN_INT64(pgstat_fetch_stat_bgwriter()->maxwritten_clean); + PG_RETURN_INT64(pgstat_fetch_stat_bgwriter()->rounds_cleaned_estimate); +} + +Datum +pg_stat_get_bgwriter_rounds_hit_limit(PG_FUNCTION_ARGS) +{ + PG_RETURN_INT64(pgstat_fetch_stat_bgwriter()->rounds_hit_limit); +} + +Datum +pg_stat_get_bgwriter_rounds_lapped_clock(PG_FUNCTION_ARGS) +{ + PG_RETURN_INT64(pgstat_fetch_stat_bgwriter()->rounds_lapped_clock); } Datum diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat index d4911ada45..64efbeaa7e 100644 --- a/src/include/catalog/pg_proc.dat +++ b/src/include/catalog/pg_proc.dat @@ -5585,11 +5585,22 @@ proargnames => '{archived_count,last_archived_wal,last_archived_time,failed_count,last_failed_wal,last_failed_time,stats_reset}', prosrc => 'pg_stat_get_archiver' }, +{ oid => '8461', + descr => 'statistics: number of times the bgwriter cleaned the number of buffers in a round estimated to be allocated in the next cycle.', + proname => 'pg_stat_get_bgwriter_rounds_cleaned_estimate', provolatile => 's', + proparallel => 'r', prorettype => 'int8', proargtypes => '', + prosrc => 'pg_stat_get_bgwriter_rounds_cleaned_estimate' }, { oid => '2773', descr => 'statistics: number of times the bgwriter stopped processing when it had written too many buffers while cleaning', - proname => 'pg_stat_get_bgwriter_maxwritten_clean', provolatile => 's', + proname => 'pg_stat_get_bgwriter_rounds_hit_limit', provolatile => 's', + proparallel => 'r', prorettype => 'int8', proargtypes => '', + prosrc => 'pg_stat_get_bgwriter_rounds_hit_limit' }, +{ oid => '8462', + descr => 'statistics: number of times the bgwriter lapped the clock sweep scan while cleaning buffers during a round', + proname => 'pg_stat_get_bgwriter_rounds_lapped_clock', provolatile => 's', proparallel => 'r', prorettype => 'int8', proargtypes => '', - prosrc => 'pg_stat_get_bgwriter_maxwritten_clean' }, + prosrc => 'pg_stat_get_bgwriter_rounds_lapped_clock' }, + { oid => '3075', descr => 'statistics: last reset for the bgwriter', proname => 'pg_stat_get_bgwriter_stat_reset_time', provolatile => 's', proparallel => 'r', prorettype => 'timestamptz', proargtypes => '', diff --git a/src/include/pgstat.h b/src/include/pgstat.h index 36d981c9ea..89bf8c6b81 100644 --- a/src/include/pgstat.h +++ b/src/include/pgstat.h @@ -524,7 +524,9 @@ typedef struct PgStat_MsgBgWriter { PgStat_MsgHdr m_hdr; - PgStat_Counter m_maxwritten_clean; + PgStat_Counter m_rounds_cleaned_estimate; + PgStat_Counter m_rounds_hit_limit; + PgStat_Counter m_rounds_lapped_clock; } PgStat_MsgBgWriter; /* ---------- @@ -967,7 +969,9 @@ typedef struct PgStat_ArchiverStats */ typedef struct PgStat_BgWriterStats { - PgStat_Counter maxwritten_clean; + PgStat_Counter rounds_cleaned_estimate; + PgStat_Counter rounds_hit_limit; + PgStat_Counter rounds_lapped_clock; TimestampTz stat_reset_timestamp; } PgStat_BgWriterStats; diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out index 97af066c6b..5373fed143 100644 --- a/src/test/regress/expected/rules.out +++ b/src/test/regress/expected/rules.out @@ -1817,7 +1817,9 @@ pg_stat_archiver| SELECT s.archived_count, s.last_failed_time, s.stats_reset FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset); -pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean, +pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_rounds_cleaned_estimate() AS rounds_cleaned_estimate, + pg_stat_get_bgwriter_rounds_hit_limit() AS rounds_hit_limit, + pg_stat_get_bgwriter_rounds_lapped_clock() AS rounds_lapped_clock, pg_stat_get_bgwriter_stat_reset_time() AS stats_reset; pg_stat_buffers| SELECT b.backend_type, b.io_path, -- 2.30.2