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Commit 74604a3

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michaelpqmichaelpq
committed
Remove buffers_backend and buffers_backend_fsync from pg_stat_checkpointer
Two attributes related to checkpointer statistics are removed in this commit: - buffers_backend, that counts the number of buffers written directly by a backend. - buffers_backend_fsync, that counts the number of times a backend had to do fsync() by its own. These are actually not checkpointer properties but backend properties. Also, pg_stat_io provides a more accurate and equivalent report of these numbers, by tracking all the I/O stats related to backends, including writes and fsyncs, so storing them in pg_stat_checkpointer was redundant. Thanks also to Robert Haas and Amit Kapila for their input. Bump catalog version. Author: Bharath Rupireddy Reviewed-by: Bertrand Drouvot, Andres Freund Discussion: https://postgr.es/m/20230210004604.mcszbscsqs3bc5nx@awork3.anarazel.de
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‎doc/src/sgml/monitoring.sgml

Copy file name to clipboardExpand all lines: doc/src/sgml/monitoring.sgml
-20Lines changed: 0 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -2953,26 +2953,6 @@ description | Waiting for a newly initialized WAL file to reach durable storage
29532953
</para></entry>
29542954
</row>
29552955

2956-
<row>
2957-
<entry role="catalog_table_entry"><para role="column_definition">
2958-
<structfield>buffers_backend</structfield> <type>bigint</type>
2959-
</para>
2960-
<para>
2961-
Number of buffers written directly by a backend
2962-
</para></entry>
2963-
</row>
2964-
2965-
<row>
2966-
<entry role="catalog_table_entry"><para role="column_definition">
2967-
<structfield>buffers_backend_fsync</structfield> <type>bigint</type>
2968-
</para>
2969-
<para>
2970-
Number of times a backend had to execute its own
2971-
<function>fsync</function> call (normally the background writer handles those
2972-
even when the backend does its own write)
2973-
</para></entry>
2974-
</row>
2975-
29762956
<row>
29772957
<entry role="catalog_table_entry"><para role="column_definition">
29782958
<structfield>buffers_alloc</structfield> <type>bigint</type>

‎src/backend/catalog/system_views.sql

Copy file name to clipboardExpand all lines: src/backend/catalog/system_views.sql
-2Lines changed: 0 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1118,8 +1118,6 @@ CREATE VIEW pg_stat_bgwriter AS
11181118
pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
11191119
pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
11201120
pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
1121-
pg_stat_get_buf_written_backend() AS buffers_backend,
1122-
pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
11231121
pg_stat_get_buf_alloc() AS buffers_alloc,
11241122
pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
11251123

‎src/backend/postmaster/checkpointer.c

Copy file name to clipboardExpand all lines: src/backend/postmaster/checkpointer.c
+2-30Lines changed: 2 additions & 30 deletions
Original file line numberDiff line numberDiff line change
@@ -91,17 +91,11 @@
9191
* requesting backends since the last checkpoint start. The flags are
9292
* chosen so that OR'ing is the correct way to combine multiple requests.
9393
*
94-
* num_backend_writes is used to count the number of buffer writes performed
95-
* by user backend processes. This counter should be wide enough that it
96-
* can't overflow during a single processing cycle. num_backend_fsync
97-
* counts the subset of those writes that also had to do their own fsync,
98-
* because the checkpointer failed to absorb their request.
99-
*
10094
* The requests array holds fsync requests sent by backends and not yet
10195
* absorbed by the checkpointer.
10296
*
103-
* Unlike the checkpoint fields, num_backend_writes, num_backend_fsync, and
104-
* the requests fields are protected by CheckpointerCommLock.
97+
* Unlike the checkpoint fields, requests related fields are protected by
98+
* CheckpointerCommLock.
10599
*----------
106100
*/
107101
typedef struct
@@ -125,9 +119,6 @@ typedef struct
125119
ConditionVariable start_cv; /* signaled when ckpt_started advances */
126120
ConditionVariable done_cv; /* signaled when ckpt_done advances */
127121

128-
uint32 num_backend_writes; /* counts user backend buffer writes */
129-
uint32 num_backend_fsync; /* counts user backend fsync calls */
130-
131122
int num_requests; /* current # of requests */
132123
int max_requests; /* allocated array size */
133124
CheckpointerRequest requests[FLEXIBLE_ARRAY_MEMBER];
@@ -1095,10 +1086,6 @@ ForwardSyncRequest(const FileTag *ftag, SyncRequestType type)
10951086

10961087
LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
10971088

1098-
/* Count all backend writes regardless of if they fit in the queue */
1099-
if (!AmBackgroundWriterProcess())
1100-
CheckpointerShmem->num_backend_writes++;
1101-
11021089
/*
11031090
* If the checkpointer isn't running or the request queue is full, the
11041091
* backend will have to perform its own fsync request. But before forcing
@@ -1108,12 +1095,6 @@ ForwardSyncRequest(const FileTag *ftag, SyncRequestType type)
11081095
(CheckpointerShmem->num_requests >= CheckpointerShmem->max_requests &&
11091096
!CompactCheckpointerRequestQueue()))
11101097
{
1111-
/*
1112-
* Count the subset of writes where backends have to do their own
1113-
* fsync
1114-
*/
1115-
if (!AmBackgroundWriterProcess())
1116-
CheckpointerShmem->num_backend_fsync++;
11171098
LWLockRelease(CheckpointerCommLock);
11181099
return false;
11191100
}
@@ -1270,15 +1251,6 @@ AbsorbSyncRequests(void)
12701251

12711252
LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
12721253

1273-
/* Transfer stats counts into pending pgstats message */
1274-
PendingCheckpointerStats.buf_written_backend
1275-
+= CheckpointerShmem->num_backend_writes;
1276-
PendingCheckpointerStats.buf_fsync_backend
1277-
+= CheckpointerShmem->num_backend_fsync;
1278-
1279-
CheckpointerShmem->num_backend_writes = 0;
1280-
CheckpointerShmem->num_backend_fsync = 0;
1281-
12821254
/*
12831255
* We try to avoid holding the lock for a long time by copying the request
12841256
* array, and processing the requests after releasing the lock.

‎src/backend/utils/activity/pgstat_checkpointer.c

Copy file name to clipboardExpand all lines: src/backend/utils/activity/pgstat_checkpointer.c
-4Lines changed: 0 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -52,8 +52,6 @@ pgstat_report_checkpointer(void)
5252
CHECKPOINTER_ACC(checkpoint_write_time);
5353
CHECKPOINTER_ACC(checkpoint_sync_time);
5454
CHECKPOINTER_ACC(buf_written_checkpoints);
55-
CHECKPOINTER_ACC(buf_written_backend);
56-
CHECKPOINTER_ACC(buf_fsync_backend);
5755
#undef CHECKPOINTER_ACC
5856

5957
pgstat_end_changecount_write(&stats_shmem->changecount);
@@ -120,7 +118,5 @@ pgstat_checkpointer_snapshot_cb(void)
120118
CHECKPOINTER_COMP(checkpoint_write_time);
121119
CHECKPOINTER_COMP(checkpoint_sync_time);
122120
CHECKPOINTER_COMP(buf_written_checkpoints);
123-
CHECKPOINTER_COMP(buf_written_backend);
124-
CHECKPOINTER_COMP(buf_fsync_backend);
125121
#undef CHECKPOINTER_COMP
126122
}

‎src/backend/utils/adt/pgstatfuncs.c

Copy file name to clipboardExpand all lines: src/backend/utils/adt/pgstatfuncs.c
-12Lines changed: 0 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -1233,18 +1233,6 @@ pg_stat_get_bgwriter_stat_reset_time(PG_FUNCTION_ARGS)
12331233
PG_RETURN_TIMESTAMPTZ(pgstat_fetch_stat_bgwriter()->stat_reset_timestamp);
12341234
}
12351235

1236-
Datum
1237-
pg_stat_get_buf_written_backend(PG_FUNCTION_ARGS)
1238-
{
1239-
PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_written_backend);
1240-
}
1241-
1242-
Datum
1243-
pg_stat_get_buf_fsync_backend(PG_FUNCTION_ARGS)
1244-
{
1245-
PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_fsync_backend);
1246-
}
1247-
12481236
Datum
12491237
pg_stat_get_buf_alloc(PG_FUNCTION_ARGS)
12501238
{

‎src/include/catalog/catversion.h

Copy file name to clipboardExpand all lines: src/include/catalog/catversion.h
+1-1Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -57,6 +57,6 @@
5757
*/
5858

5959
/* yyyymmddN */
60-
#define CATALOG_VERSION_NO 202310261
60+
#define CATALOG_VERSION_NO 202310271
6161

6262
#endif

‎src/include/catalog/pg_proc.dat

Copy file name to clipboardExpand all lines: src/include/catalog/pg_proc.dat
-9Lines changed: 0 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -5738,15 +5738,6 @@
57385738
proname => 'pg_stat_get_checkpoint_sync_time', provolatile => 's',
57395739
proparallel => 'r', prorettype => 'float8', proargtypes => '',
57405740
prosrc => 'pg_stat_get_checkpoint_sync_time' },
5741-
{ oid => '2775', descr => 'statistics: number of buffers written by backends',
5742-
proname => 'pg_stat_get_buf_written_backend', provolatile => 's',
5743-
proparallel => 'r', prorettype => 'int8', proargtypes => '',
5744-
prosrc => 'pg_stat_get_buf_written_backend' },
5745-
{ oid => '3063',
5746-
descr => 'statistics: number of backend buffer writes that did their own fsync',
5747-
proname => 'pg_stat_get_buf_fsync_backend', provolatile => 's',
5748-
proparallel => 'r', prorettype => 'int8', proargtypes => '',
5749-
prosrc => 'pg_stat_get_buf_fsync_backend' },
57505741
{ oid => '2859', descr => 'statistics: number of buffer allocations',
57515742
proname => 'pg_stat_get_buf_alloc', provolatile => 's', proparallel => 'r',
57525743
prorettype => 'int8', proargtypes => '', prosrc => 'pg_stat_get_buf_alloc' },

‎src/include/pgstat.h

Copy file name to clipboardExpand all lines: src/include/pgstat.h
-2Lines changed: 0 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -265,8 +265,6 @@ typedef struct PgStat_CheckpointerStats
265265
PgStat_Counter checkpoint_write_time; /* times in milliseconds */
266266
PgStat_Counter checkpoint_sync_time;
267267
PgStat_Counter buf_written_checkpoints;
268-
PgStat_Counter buf_written_backend;
269-
PgStat_Counter buf_fsync_backend;
270268
} PgStat_CheckpointerStats;
271269

272270

‎src/test/regress/expected/rules.out

Copy file name to clipboardExpand all lines: src/test/regress/expected/rules.out
-2Lines changed: 0 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1823,8 +1823,6 @@ pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints
18231823
pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
18241824
pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
18251825
pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
1826-
pg_stat_get_buf_written_backend() AS buffers_backend,
1827-
pg_stat_get_buf_fsync_backend() AS buffers_backend_fsync,
18281826
pg_stat_get_buf_alloc() AS buffers_alloc,
18291827
pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
18301828
pg_stat_database| SELECT oid AS datid,

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