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Refactor some code related to backend statistics
This commit changes the way pending backend statistics are tracked by moving them into a new structure called PgStat_BackendPending, removing PgStat_BackendPendingIO. PgStat_BackendPending currently only includes PgStat_PendingIO for the pending I/O stats. pgstat_flush_backend() is extended with a "flags" argument to control which parts of the stats of a backend should be flushed. With this refactoring, it becomes easier to plug into backend statistics more data. A patch to add information related to WAL in this stats kind is under discussion. Author: Bertrand Drouvot Discussion: https://postgr.es/m/Z3zqc4o09dM/Ezyz@ip-10-97-1-34.eu-west-3.compute.internal
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8 files changed

+76
-35
lines changed

8 files changed

+76
-35
lines changed

‎src/backend/utils/activity/pgstat.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -370,7 +370,7 @@ static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE]
370370
.shared_size = sizeof(PgStatShared_Backend),
371371
.shared_data_off = offsetof(PgStatShared_Backend, stats),
372372
.shared_data_len = sizeof(((PgStatShared_Backend *) 0)->stats),
373-
.pending_size = sizeof(PgStat_BackendPendingIO),
373+
.pending_size = sizeof(PgStat_BackendPending),
374374

375375
.flush_pending_cb = pgstat_backend_flush_cb,
376376
.reset_timestamp_cb = pgstat_backend_reset_timestamp_cb,

‎src/backend/utils/activity/pgstat_backend.c

Lines changed: 49 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -39,23 +39,21 @@ pgstat_fetch_stat_backend(ProcNumber procNumber)
3939
}
4040

4141
/*
42-
* Flush out locally pending backend statistics
43-
*
44-
* If no stats have been recorded, this function returns false.
42+
* Flush out locally pending backend IO statistics. Locking is managed
43+
* by the caller.
4544
*/
46-
bool
47-
pgstat_backend_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
45+
static void
46+
pgstat_flush_backend_entry_io(PgStat_EntryRef *entry_ref)
4847
{
49-
PgStatShared_Backend *shbackendioent;
50-
PgStat_BackendPendingIO *pendingent;
48+
PgStatShared_Backend *shbackendent;
49+
PgStat_BackendPending *pendingent;
5150
PgStat_BktypeIO *bktype_shstats;
51+
PgStat_PendingIO *pending_io;
5252

53-
if (!pgstat_lock_entry(entry_ref, nowait))
54-
return false;
55-
56-
shbackendioent = (PgStatShared_Backend *) entry_ref->shared_stats;
57-
bktype_shstats = &shbackendioent->stats.stats;
58-
pendingent = (PgStat_BackendPendingIO *) entry_ref->pending;
53+
shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
54+
pendingent = (PgStat_BackendPending *) entry_ref->pending;
55+
bktype_shstats = &shbackendent->stats.io_stats;
56+
pending_io = &pendingent->pending_io;
5957

6058
for (int io_object = 0; io_object < IOOBJECT_NUM_TYPES; io_object++)
6159
{
@@ -66,26 +64,57 @@ pgstat_backend_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
6664
instr_time time;
6765

6866
bktype_shstats->counts[io_object][io_context][io_op] +=
69-
pendingent->counts[io_object][io_context][io_op];
67+
pending_io->counts[io_object][io_context][io_op];
7068

71-
time = pendingent->pending_times[io_object][io_context][io_op];
69+
time = pending_io->pending_times[io_object][io_context][io_op];
7270

7371
bktype_shstats->times[io_object][io_context][io_op] +=
7472
INSTR_TIME_GET_MICROSEC(time);
7573
}
7674
}
7775
}
76+
}
77+
78+
/*
79+
* Wrapper routine to flush backend statistics.
80+
*/
81+
static bool
82+
pgstat_flush_backend_entry(PgStat_EntryRef *entry_ref, bool nowait,
83+
bits32 flags)
84+
{
85+
if (!pgstat_tracks_backend_bktype(MyBackendType))
86+
return false;
87+
88+
if (!pgstat_lock_entry(entry_ref, nowait))
89+
return false;
90+
91+
/* Flush requested statistics */
92+
if (flags & PGSTAT_BACKEND_FLUSH_IO)
93+
pgstat_flush_backend_entry_io(entry_ref);
7894

7995
pgstat_unlock_entry(entry_ref);
8096

8197
return true;
8298
}
8399

84100
/*
85-
* Simpler wrapper of pgstat_backend_flush_cb()
101+
* Callback to flush out locally pending backend statistics.
102+
*
103+
* If no stats have been recorded, this function returns false.
104+
*/
105+
bool
106+
pgstat_backend_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
107+
{
108+
return pgstat_flush_backend_entry(entry_ref, nowait, PGSTAT_BACKEND_FLUSH_ALL);
109+
}
110+
111+
/*
112+
* Flush out locally pending backend statistics
113+
*
114+
* "flags" parameter controls which statistics to flush.
86115
*/
87116
void
88-
pgstat_flush_backend(bool nowait)
117+
pgstat_flush_backend(bool nowait, bits32 flags)
89118
{
90119
PgStat_EntryRef *entry_ref;
91120

@@ -94,7 +123,7 @@ pgstat_flush_backend(bool nowait)
94123

95124
entry_ref = pgstat_get_entry_ref(PGSTAT_KIND_BACKEND, InvalidOid,
96125
MyProcNumber, false, NULL);
97-
(void) pgstat_backend_flush_cb(entry_ref, nowait);
126+
(void) pgstat_flush_backend_entry(entry_ref, nowait, flags);
98127
}
99128

100129
/*
@@ -119,9 +148,9 @@ pgstat_create_backend(ProcNumber procnum)
119148
}
120149

121150
/*
122-
* Find or create a local PgStat_BackendPendingIO entry for proc number.
151+
* Find or create a local PgStat_BackendPending entry for proc number.
123152
*/
124-
PgStat_BackendPendingIO *
153+
PgStat_BackendPending *
125154
pgstat_prep_backend_pending(ProcNumber procnum)
126155
{
127156
PgStat_EntryRef *entry_ref;

‎src/backend/utils/activity/pgstat_io.c

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -81,10 +81,10 @@ pgstat_count_io_op_n(IOObject io_object, IOContext io_context, IOOp io_op, uint3
8181

8282
if (pgstat_tracks_backend_bktype(MyBackendType))
8383
{
84-
PgStat_PendingIO *entry_ref;
84+
PgStat_BackendPending *entry_ref;
8585

8686
entry_ref = pgstat_prep_backend_pending(MyProcNumber);
87-
entry_ref->counts[io_object][io_context][io_op] += cnt;
87+
entry_ref->pending_io.counts[io_object][io_context][io_op] += cnt;
8888
}
8989

9090
PendingIOStats.counts[io_object][io_context][io_op] += cnt;
@@ -151,10 +151,10 @@ pgstat_count_io_op_time(IOObject io_object, IOContext io_context, IOOp io_op,
151151

152152
if (pgstat_tracks_backend_bktype(MyBackendType))
153153
{
154-
PgStat_PendingIO *entry_ref;
154+
PgStat_BackendPending *entry_ref;
155155

156156
entry_ref = pgstat_prep_backend_pending(MyProcNumber);
157-
INSTR_TIME_ADD(entry_ref->pending_times[io_object][io_context][io_op],
157+
INSTR_TIME_ADD(entry_ref->pending_io.pending_times[io_object][io_context][io_op],
158158
io_time);
159159
}
160160
}

‎src/backend/utils/activity/pgstat_relation.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -264,7 +264,7 @@ pgstat_report_vacuum(Oid tableoid, bool shared,
264264
* VACUUM command has processed all tables and committed.
265265
*/
266266
pgstat_flush_io(false);
267-
pgstat_flush_backend(false);
267+
pgstat_flush_backend(false, PGSTAT_BACKEND_FLUSH_IO);
268268
}
269269

270270
/*
@@ -351,7 +351,7 @@ pgstat_report_analyze(Relation rel,
351351

352352
/* see pgstat_report_vacuum() */
353353
pgstat_flush_io(false);
354-
pgstat_flush_backend(false);
354+
pgstat_flush_backend(false, PGSTAT_BACKEND_FLUSH_IO);
355355
}
356356

357357
/*

‎src/backend/utils/adt/pgstatfuncs.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1544,7 +1544,7 @@ pg_stat_get_backend_io(PG_FUNCTION_ARGS)
15441544
if (bktype == B_INVALID)
15451545
return (Datum) 0;
15461546

1547-
bktype_stats = &backend_stats->stats;
1547+
bktype_stats = &backend_stats->io_stats;
15481548

15491549
/*
15501550
* In Assert builds, we can afford an extra loop through all of the

‎src/include/pgstat.h

Lines changed: 13 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -375,15 +375,24 @@ typedef struct PgStat_IO
375375
PgStat_BktypeIO stats[BACKEND_NUM_TYPES];
376376
} PgStat_IO;
377377

378-
/* Backend statistics store the same amount of IO data as PGSTAT_KIND_IO */
379-
typedef PgStat_PendingIO PgStat_BackendPendingIO;
380-
381378
typedef struct PgStat_Backend
382379
{
383380
TimestampTz stat_reset_timestamp;
384-
PgStat_BktypeIO stats;
381+
PgStat_BktypeIO io_stats;
385382
} PgStat_Backend;
386383

384+
/* ---------
385+
* PgStat_BackendPending Non-flushed backend stats.
386+
* ---------
387+
*/
388+
typedef struct PgStat_BackendPending
389+
{
390+
/*
391+
* Backend statistics store the same amount of IO data as PGSTAT_KIND_IO.
392+
*/
393+
PgStat_PendingIO pending_io;
394+
} PgStat_BackendPending;
395+
387396
typedef struct PgStat_StatDBEntry
388397
{
389398
PgStat_Counter xact_commit;

‎src/include/utils/pgstat_internal.h

Lines changed: 5 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -613,9 +613,12 @@ extern void pgstat_archiver_snapshot_cb(void);
613613
* Functions in pgstat_backend.c
614614
*/
615615

616-
extern void pgstat_flush_backend(bool nowait);
616+
/* flags for pgstat_flush_backend() */
617+
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
618+
#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO)
617619

618-
extern PgStat_BackendPendingIO *pgstat_prep_backend_pending(ProcNumber procnum);
620+
extern void pgstat_flush_backend(bool nowait, bits32 flags);
621+
extern PgStat_BackendPending *pgstat_prep_backend_pending(ProcNumber procnum);
619622
extern bool pgstat_backend_flush_cb(PgStat_EntryRef *entry_ref, bool nowait);
620623
extern void pgstat_backend_reset_timestamp_cb(PgStatShared_Common *header, TimestampTz ts);
621624

‎src/tools/pgindent/typedefs.list

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2140,7 +2140,7 @@ PgStatShared_Subscription
21402140
PgStatShared_Wal
21412141
PgStat_ArchiverStats
21422142
PgStat_Backend
2143-
PgStat_BackendPendingIO
2143+
PgStat_BackendPending
21442144
PgStat_BackendSubEntry
21452145
PgStat_BgWriterStats
21462146
PgStat_BktypeIO

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