10BC0 Allow parallel create index to accumulate buffer usage stats. · postgrespro/postgres_cluster@5c71362 · GitHub
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Amit Kapila
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Allow parallel create index to accumulate buffer usage stats.
Currently, we don't account for buffer usage incurred by parallel workers for parallel create index.  This commit allows each worker to record the buffer usage stats and leader backend to accumulate that stats at the end of the operation.  This will allow pg_stat_statements to display correct buffer usage stats for (parallel) create index command. Reported-by: Julien Rouhaud Author: Sawada Masahiko Reviewed-by: Dilip Kumar, Julien Rouhaud and Amit Kapila Backpatch-through: 11, where this was introduced Discussion: https://postgr.es/m/20200328151721.GB12854@nol
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2 files changed

+28
-16
lines changed

2 files changed

+28
-16
lines changed

‎src/backend/access/nbtree/nbtsort.c‎

Lines changed: 25 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -71,6 +71,7 @@
7171
#define PARALLEL_KEY_TUPLESORT_SPOOL2 UINT64CONST(0xA000000000000003)
7272
#define PARALLEL_KEY_QUERY_TEXT UINT64CONST(0xA000000000000004)
7373
#define PARALLEL_KEY_WAL_USAGE UINT64CONST(0xA000000000000005)
74+
#define PARALLEL_KEY_BUFFER_USAGE UINT64CONST(0xA000000000000006)
7475

7576
/*
7677
* DISABLE_LEADER_PARTICIPATION disables the leader's participation in
@@ -194,6 +195,7 @@ typedef struct BTLeader
194195
Sharedsort *sharedsort2;
195196
Snapshot snapshot;
196197
WalUsage *walusage;
198+
BufferUsage *bufferusage;
197199
} BTLeader;
198200

199201
/*
@@ -1457,6 +1459,7 @@ _bt_begin_parallel(BTBuildState *buildstate, bool isconcurrent, int request)
14571459
BTSpool *btspool = buildstate->spool;
14581460
BTLeader *btleader = (BTLeader *) palloc0(sizeof(BTLeader));
14591461
WalUsage *walusage;
1462+
BufferUsage *bufferusage;
14601463
bool leaderparticipates = true;
14611464
char *sharedquery;
14621465
int querylen;
@@ -1510,16 +1513,19 @@ _bt_begin_parallel(BTBuildState *buildstate, bool isconcurrent, int request)
15101513
}
15111514

15121515
/*
1513-
* Estimate space for WalUsage -- PARALLEL_KEY_WAL_USAGE
1516+
* Estimate space for WalUsage and BufferUsage -- PARALLEL_KEY_WAL_USAGE
1517+
* and PARALLEL_KEY_BUFFER_USAGE.
15141518
*
1515-
* WalUsage during execution of maintenance command can be used by an
1516-
* extension that reports the WAL usage, such as pg_stat_statements. We
1517-
* have no way of knowing whether anyone's looking at pgWalUsage, so do it
1518-
* unconditionally.
1519+
* If there are no extensions loaded that care, we could skip this. We
1520+
* have no way of knowing whether anyone's looking at pgWalUsage or
1521+
* pgBufferUsage, so do it unconditionally.
15191522
*/
15201523
shm_toc_estimate_chunk(&pcxt->estimator,
15211524
mul_size(sizeof(WalUsage), pcxt->nworkers));
15221525
shm_toc_estimate_keys(&pcxt->estimator, 1);
1526+
shm_toc_estimate_chunk(&pcxt->estimator,
1527+
mul_size(sizeof(BufferUsage), pcxt->nworkers));
1528+
shm_toc_estimate_keys(&pcxt->estimator, 1);
15231529

15241530
/* Finally, estimate PARALLEL_KEY_QUERY_TEXT space */
15251531
querylen = strlen(debug_query_string);
@@ -1592,10 +1598,16 @@ _bt_begin_parallel(BTBuildState *buildstate, bool isconcurrent, int request)
15921598
memcpy(sharedquery, debug_query_string, querylen + 1);
15931599
shm_toc_insert(pcxt->toc, PARALLEL_KEY_QUERY_TEXT, sharedquery);
15941600

1595-
/* Allocate space for each worker's WalUsage; no need to initialize */
1601+
/*
1602+
* Allocate space for each worker's WalUsage and BufferUsage; no need to
1603+
* initialize.
1604+
*/
15961605
walusage = shm_toc_allocate(pcxt->toc,
15971606
mul_size(sizeof(WalUsage), pcxt->nworkers));
15981607
shm_toc_insert(pcxt->toc, PARALLEL_KEY_WAL_USAGE, walusage);
1608+
bufferusage = shm_toc_allocate(pcxt->toc,
1609+
mul_size(sizeof(BufferUsage), pcxt->nworkers));
1610+
shm_toc_insert(pcxt->toc, PARALLEL_KEY_BUFFER_USAGE, bufferusage);
15991611

16001612
/* Launch workers, saving status for leader/caller */
16011613
LaunchParallelWorkers(pcxt);
@@ -1608,6 +1620,7 @@ _bt_begin_parallel(BTBuildState *buildstate, bool isconcurrent, int request)
16081620
btleader->sharedsort2 = sharedsort2;
16091621
btleader->snapshot = snapshot;
16101622
btleader->walusage = walusage;
1623+
btleader->bufferusage = bufferusage;
16111624

16121625
/* If no workers were successfully launched, back out (do serial build) */
16131626
if (pcxt->nworkers_launched == 0)
@@ -1646,7 +1659,7 @@ _bt_end_parallel(BTLeader *btleader)
16461659
* or we might get incomplete data.)
16471660
*/
16481661
for (i = 0; i < btleader->pcxt->nworkers_launched; i++)
1649-
InstrAccumParallelQuery(NULL, &btleader->walusage[i]);
1662+
InstrAccumParallelQuery(&btleader->bufferusage[i], &btleader->walusage[i]);
16501663

16511664
/* Free last reference to MVCC snapshot, if one was used */
16521665
if (IsMVCCSnapshot(btleader->snapshot))
@@ -1779,6 +1792,7 @@ _bt_parallel_build_main(dsm_segment *seg, shm_toc *toc)
17791792
LOCKMODE heapLockmode;
17801793
LOCKMODE indexLockmode;
17811794
WalUsage *walusage;
1795+
BufferUsage *bufferusage;
17821796
int sortmem;
17831797

17841798
#ifdef BTREE_BUILD_STATS
@@ -1848,9 +1862,11 @@ _bt_parallel_build_main(dsm_segment *seg, shm_toc *toc)
18481862
_bt_parallel_scan_and_sort(btspool, btspool2, btshared, sharedsort,
18491863
sharedsort2, sortmem, false);
18501864

1851-
/* Report WAL usage during parallel execution */
1865+
/* Report WAL/buffer usage during parallel execution */
1866+
bufferusage = shm_toc_lookup(toc, PARALLEL_KEY_BUFFER_USAGE, false);
18521867
walusage = shm_toc_lookup(toc, PARALLEL_KEY_WAL_USAGE, false);
1853-
InstrEndParallelQuery(NULL, &walusage[ParallelWorkerNumber]);
1868+
InstrEndParallelQuery(&bufferusage[ParallelWorkerNumber],
1869+
&walusage[ParallelWorkerNumber]);
18541870

18551871
#ifdef BTREE_BUILD_STATS
18561872
if (log_btree_build_stats)

‎src/backend/executor/instrument.c‎

Lines changed: 3 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -188,11 +188,8 @@ InstrStartParallelQuery(void)
188188
void
189189
InstrEndParallelQuery(BufferUsage *bufusage, WalUsage *walusage)
190190
{
191-
if (bufusage)
192-
{
193-
memset(bufusage, 0, sizeof(BufferUsage));
194-
BufferUsageAccumDiff(bufusage, &pgBufferUsage, &save_pgBufferUsage);
195-
}
191+
memset(bufusage, 0, sizeof(BufferUsage));
192+
BufferUsageAccumDiff(bufusage, &pgBufferUsage, &save_pgBufferUsage);
196193
memset(walusage, 0, sizeof(WalUsage));
197194
WalUsageAccumDiff(walusage, &pgWalUsage, &save_pgWalUsage);
198195
}
@@ -201,8 +198,7 @@ InstrEndParallelQuery(BufferUsage *bufusage, WalUsage *walusage)
201198
void
202199
InstrAccumParallelQuery(BufferUsage *bufusage, WalUsage *walusage)
203200
{
204-
if (bufusage)
205-
BufferUsageAdd(&pgBufferUsage, bufusage);
201+
BufferUsageAdd(&pgBufferUsage, bufusage);
206202
WalUsageAdd(&pgWalUsage, walusage);
207203
}
208204

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