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Commit81ca868

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Improve management of SLRU statistics collection.
Instead of re-identifying which statistics bucket to use for a givenSLRU on every counter increment, do it once during shmem initialization.This saves a fair number of cycles, and there's no real cost becausewe could not have a bucket assignment that varies over time or acrossbackends anyway.Also, get rid of the ill-considered decision to let pgstat.c prydirectly into SLRU's shared state; it's cleaner just to have slru.cpass the stats bucket number.In consequence of these changes, there's no longer any need to storean SLRU's LWLock tranche info in shared memory, so get rid of that,making this a net reduction in shmem consumption. (That partlyrevertsfe702a7.)This is basically code review for28cac71, so I also cleaned upsome comments, removed a dangling extern declaration, fixed somethings that should be static and/or const, etc.Discussion:https://postgr.es/m/3618.1589313035@sss.pgh.pa.us
1 parent850196b commit81ca868

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5 files changed

+76
-85
lines changed

5 files changed

+76
-85
lines changed

‎src/backend/access/transam/slru.c

Lines changed: 12 additions & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -191,6 +191,8 @@ SimpleLruInit(SlruCtl ctl, const char *name, int nslots, int nlsns,
191191

192192
/* shared->latest_page_number will be set later */
193193

194+
shared->slru_stats_idx=pgstat_slru_index(name);
195+
194196
ptr= (char*)shared;
195197
offset=MAXALIGN(sizeof(SlruSharedData));
196198
shared->page_buffer= (char**) (ptr+offset);
@@ -214,15 +216,11 @@ SimpleLruInit(SlruCtl ctl, const char *name, int nslots, int nlsns,
214216
offset+=MAXALIGN(nslots*nlsns*sizeof(XLogRecPtr));
215217
}
216218

217-
Assert(strlen(name)+1<SLRU_MAX_NAME_LENGTH);
218-
strlcpy(shared->lwlock_tranche_name,name,SLRU_MAX_NAME_LENGTH);
219-
shared->lwlock_tranche_id=tranche_id;
220-
221219
ptr+=BUFFERALIGN(offset);
222220
for (slotno=0;slotno<nslots;slotno++)
223221
{
224222
LWLockInitialize(&shared->buffer_locks[slotno].lock,
225-
shared->lwlock_tranche_id);
223+
tranche_id);
226224

227225
shared->page_buffer[slotno]=ptr;
228226
shared->page_status[slotno]=SLRU_PAGE_EMPTY;
@@ -238,8 +236,7 @@ SimpleLruInit(SlruCtl ctl, const char *name, int nslots, int nlsns,
238236
Assert(found);
239237

240238
/* Register SLRU tranche in the main tranches array */
241-
LWLockRegisterTranche(shared->lwlock_tranche_id,
242-
shared->lwlock_tranche_name);
239+
LWLockRegisterTranche(tranche_id,name);
243240

244241
/*
245242
* Initialize the unshared control struct, including directory path. We
@@ -287,7 +284,7 @@ SimpleLruZeroPage(SlruCtl ctl, int pageno)
287284
shared->latest_page_number=pageno;
288285

289286
/* update the stats counter of zeroed pages */
290-
pgstat_count_slru_page_zeroed(ctl);
287+
pgstat_count_slru_page_zeroed(shared->slru_stats_idx);
291288

292289
returnslotno;
293290
}
@@ -408,7 +405,7 @@ SimpleLruReadPage(SlruCtl ctl, int pageno, bool write_ok,
408405
SlruRecentlyUsed(shared,slotno);
409406

410407
/* update the stats counter of pages found in the SLRU */
411-
pgstat_count_slru_page_hit(ctl);
408+
pgstat_count_slru_page_hit(shared->slru_stats_idx);
412409

413410
returnslotno;
414411
}
@@ -453,7 +450,7 @@ SimpleLruReadPage(SlruCtl ctl, int pageno, bool write_ok,
453450
SlruRecentlyUsed(shared,slotno);
454451

455452
/* update the stats counter of pages not found in SLRU */
456-
pgstat_count_slru_page_read(ctl);
453+
pgstat_count_slru_page_read(shared->slru_stats_idx);
457454

458455
returnslotno;
459456
}
@@ -493,7 +490,7 @@ SimpleLruReadPage_ReadOnly(SlruCtl ctl, int pageno, TransactionId xid)
493490
SlruRecentlyUsed(shared,slotno);
494491

495492
/* update the stats counter of pages found in the SLRU */
496-
pgstat_count_slru_page_hit(ctl);
493+
pgstat_count_slru_page_hit(shared->slru_stats_idx);
497494

498495
returnslotno;
499496
}
@@ -612,7 +609,7 @@ SimpleLruDoesPhysicalPageExist(SlruCtl ctl, int pageno)
612609
off_tendpos;
613610

614611
/* update the stats counter of checked pages */
615-
pgstat_count_slru_page_exists(ctl);
612+
pgstat_count_slru_page_exists(ctl->shared->slru_stats_idx);
616613

617614
SlruFileName(ctl,path,segno);
618615

@@ -749,7 +746,7 @@ SlruPhysicalWritePage(SlruCtl ctl, int pageno, int slotno, SlruFlush fdata)
749746
intfd=-1;
750747

751748
/* update the stats counter of written pages */
752-
pgstat_count_slru_page_written(ctl);
749+
pgstat_count_slru_page_written(shared->slru_stats_idx);
753750

754751
/*
755752
* Honor the write-WAL-before-data rule, if appropriate, so that we do not
@@ -1147,7 +1144,7 @@ SimpleLruFlush(SlruCtl ctl, bool allow_redirtied)
11471144
boolok;
11481145

11491146
/* update the stats counter of flushes */
1150-
pgstat_count_slru_flush(ctl);
1147+
pgstat_count_slru_flush(shared->slru_stats_idx);
11511148

11521149
/*
11531150
* Find and write dirty pages
@@ -1211,7 +1208,7 @@ SimpleLruTruncate(SlruCtl ctl, int cutoffPage)
12111208
intslotno;
12121209

12131210
/* update the stats counter of truncates */
1214-
pgstat_count_slru_truncate(ctl);
1211+
pgstat_count_slru_truncate(shared->slru_stats_idx);
12151212

12161213
/*
12171214
* The cutoff point is the start of the segment containing cutoffPage.

‎src/backend/postmaster/pgstat.c

Lines changed: 50 additions & 46 deletions
Original file line numberDiff line numberDiff line change
@@ -142,24 +142,30 @@ char *pgstat_stat_tmpname = NULL;
142142
PgStat_MsgBgWriterBgWriterStats;
143143

144144
/*
145-
* SLRU statistics counters (unused in other processes) stored directly in
146-
* stats structure so it can be sent without needing to copy things around.
147-
* We assume this inits to zeroes. There is no central registry of SLRUs,
148-
* so we use this fixed list instead.
149-
*
150-
* There's a separte entry for each SLRU we have. The "other" entry is used
151-
* for all SLRUs without an explicit entry (e.g. SLRUs in extensions).
152-
*/
153-
staticchar*slru_names[]= {"async","clog","commit_timestamp",
154-
"multixact_offset","multixact_member",
155-
"oldserxid","subtrans",
156-
"other"/* has to be last */};
145+
* List of SLRU names that we keep stats for. There is no central registry of
146+
* SLRUs, so we use this fixed list instead. The "other" entry is used for
147+
* all SLRUs without an explicit entry (e.g. SLRUs in extensions).
148+
*/
149+
staticconstchar*constslru_names[]= {
150+
"async",
151+
"clog",
152+
"commit_timestamp",
153+
"multixact_offset",
154+
"multixact_member",
155+
"oldserxid",
156+
"subtrans",
157+
"other"/* has to be last */
158+
};
159+
160+
#defineSLRU_NUM_ELEMENTSlengthof(slru_names)
157161

158-
/* number of elemenents of slru_name array */
159-
#defineSLRU_NUM_ELEMENTS(sizeof(slru_names) / sizeof(char *))
160-
161-
/* entries in the same order as slru_names */
162-
PgStat_MsgSLRUSLRUStats[SLRU_NUM_ELEMENTS];
162+
/*
163+
* SLRU statistics counts waiting to be sent to the collector. These are
164+
* stored directly in stats message format so they can be sent without needing
165+
* to copy things around. We assume this variable inits to zeroes. Entries
166+
* are one-to-one with slru_names[].
167+
*/
168+
staticPgStat_MsgSLRUSLRUStats[SLRU_NUM_ELEMENTS];
163169

164170
/* ----------
165171
* Local data
@@ -4411,12 +4417,10 @@ pgstat_send_bgwriter(void)
44114417
staticvoid
44124418
pgstat_send_slru(void)
44134419
{
4414-
inti;
4415-
44164420
/* We assume this initializes to zeroes */
44174421
staticconstPgStat_MsgSLRUall_zeroes;
44184422

4419-
for (i=0;i<SLRU_NUM_ELEMENTS;i++)
4423+
for (inti=0;i<SLRU_NUM_ELEMENTS;i++)
44204424
{
44214425
/*
44224426
* This function can be called even if nothing at all has happened. In
@@ -6705,15 +6709,13 @@ pgstat_slru_index(const char *name)
67056709
* in which case this returns NULL. This allows writing code that does not
67066710
* know the number of entries in advance.
67076711
*/
6708-
char*
6709-
pgstat_slru_name(intidx)
6712+
constchar*
6713+
pgstat_slru_name(intslru_idx)
67106714
{
6711-
Assert(idx >=0);
6712-
6713-
if (idx >=SLRU_NUM_ELEMENTS)
6715+
if (slru_idx<0||slru_idx >=SLRU_NUM_ELEMENTS)
67146716
returnNULL;
67156717

6716-
returnslru_names[idx];
6718+
returnslru_names[slru_idx];
67176719
}
67186720

67196721
/*
@@ -6722,54 +6724,56 @@ pgstat_slru_name(int idx)
67226724
* Returns pointer to entry with counters for given SLRU (based on the name
67236725
* stored in SlruCtl as lwlock tranche name).
67246726
*/
6725-
staticPgStat_MsgSLRU*
6726-
slru_entry(SlruCtlctl)
6727+
staticinlinePgStat_MsgSLRU*
6728+
slru_entry(intslru_idx)
67276729
{
6728-
intidx=pgstat_slru_index(ctl->shared->lwlock_tranche_name);
6729-
6730-
Assert((idx >=0)&& (idx<SLRU_NUM_ELEMENTS));
6730+
Assert((slru_idx >=0)&& (slru_idx<SLRU_NUM_ELEMENTS));
67316731

6732-
return&SLRUStats[idx];
6732+
return&SLRUStats[slru_idx];
67336733
}
67346734

6735+
/*
6736+
* SLRU statistics count accumulation functions --- called from slru.c
6737+
*/
6738+
67356739
void
6736-
pgstat_count_slru_page_zeroed(SlruCtlctl)
6740+
pgstat_count_slru_page_zeroed(intslru_idx)
67376741
{
6738-
slru_entry(ctl)->m_blocks_zeroed+=1;
6742+
slru_entry(slru_idx)->m_blocks_zeroed+=1;
67396743
}
67406744

67416745
void
6742-
pgstat_count_slru_page_hit(SlruCtlctl)
6746+
pgstat_count_slru_page_hit(intslru_idx)
67436747
{
6744-
slru_entry(ctl)->m_blocks_hit+=1;
6748+
slru_entry(slru_idx)->m_blocks_hit+=1;
67456749
}
67466750

67476751
void
6748-
pgstat_count_slru_page_exists(SlruCtlctl)
6752+
pgstat_count_slru_page_exists(intslru_idx)
67496753
{
6750-
slru_entry(ctl)->m_blocks_exists+=1;
6754+
slru_entry(slru_idx)->m_blocks_exists+=1;
67516755
}
67526756

67536757
void
6754-
pgstat_count_slru_page_read(SlruCtlctl)
6758+
pgstat_count_slru_page_read(intslru_idx)
67556759
{
6756-
slru_entry(ctl)->m_blocks_read+=1;
6760+
slru_entry(slru_idx)->m_blocks_read+=1;
67576761
}
67586762

67596763
void
6760-
pgstat_count_slru_page_written(SlruCtlctl)
6764+
pgstat_count_slru_page_written(intslru_idx)
67616765
{
6762-
slru_entry(ctl)->m_blocks_written+=1;
6766+
slru_entry(slru_idx)->m_blocks_written+=1;
67636767
}
67646768

67656769
void
6766-
pgstat_count_slru_flush(SlruCtlctl)
6770+
pgstat_count_slru_flush(intslru_idx)
67676771
{
6768-
slru_entry(ctl)->m_flush+=1;
6772+
slru_entry(slru_idx)->m_flush+=1;
67696773
}
67706774

67716775
void
6772-
pgstat_count_slru_truncate(SlruCtlctl)
6776+
pgstat_count_slru_truncate(intslru_idx)
67736777
{
6774-
slru_entry(ctl)->m_truncate+=1;
6778+
slru_entry(slru_idx)->m_truncate+=1;
67756779
}

‎src/backend/utils/adt/pgstatfuncs.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1739,7 +1739,7 @@ pg_stat_get_slru(PG_FUNCTION_ARGS)
17391739
Datumvalues[PG_STAT_GET_SLRU_COLS];
17401740
boolnulls[PG_STAT_GET_SLRU_COLS];
17411741
PgStat_SLRUStatsstat=stats[i];
1742-
char*name;
1742+
constchar*name;
17431743

17441744
name=pgstat_slru_name(i);
17451745

‎src/include/access/slru.h

Lines changed: 3 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -32,9 +32,6 @@
3232
*/
3333
#defineSLRU_PAGES_PER_SEGMENT32
3434

35-
/* Maximum length of an SLRU name */
36-
#defineSLRU_MAX_NAME_LENGTH32
37-
3835
/*
3936
* Page status codes. Note that these do not include the "dirty" bit.
4037
* page_dirty can be true only in the VALID or WRITE_IN_PROGRESS states;
@@ -68,6 +65,7 @@ typedef struct SlruSharedData
6865
bool*page_dirty;
6966
int*page_number;
7067
int*page_lru_count;
68+
LWLockPadded*buffer_locks;
7169

7270
/*
7371
* Optional array of WAL flush LSNs associated with entries in the SLRU
@@ -98,10 +96,8 @@ typedef struct SlruSharedData
9896
*/
9997
intlatest_page_number;
10098

101-
/* LWLocks */
102-
intlwlock_tranche_id;
103-
charlwlock_tranche_name[SLRU_MAX_NAME_LENGTH];
104-
LWLockPadded*buffer_locks;
99+
/* SLRU's index for statistics purposes (might not be unique) */
100+
intslru_stats_idx;
105101
}SlruSharedData;
106102

107103
typedefSlruSharedData*SlruShared;

‎src/include/pgstat.h

Lines changed: 10 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,6 @@
1111
#ifndefPGSTAT_H
1212
#definePGSTAT_H
1313

14-
#include"access/slru.h"
1514
#include"datatype/timestamp.h"
1615
#include"libpq/pqcomm.h"
1716
#include"miscadmin.h"
@@ -438,7 +437,7 @@ typedef struct PgStat_MsgBgWriter
438437
}PgStat_MsgBgWriter;
439438

440439
/* ----------
441-
* PgStat_MsgSLRUSent bythe SLRU to update statistics.
440+
* PgStat_MsgSLRUSent bya backend to update SLRU statistics.
442441
* ----------
443442
*/
444443
typedefstructPgStat_MsgSLRU
@@ -1260,11 +1259,6 @@ extern char *pgstat_stat_filename;
12601259
*/
12611260
externPgStat_MsgBgWriterBgWriterStats;
12621261

1263-
/*
1264-
* SLRU statistics counters are updated directly by slru.
1265-
*/
1266-
externPgStat_MsgSLRUSlruStats[];
1267-
12681262
/*
12691263
* Updated by pgstat_count_buffer_*_time macros
12701264
*/
@@ -1480,14 +1474,14 @@ extern PgStat_ArchiverStats *pgstat_fetch_stat_archiver(void);
14801474
externPgStat_GlobalStats*pgstat_fetch_global(void);
14811475
externPgStat_SLRUStats*pgstat_fetch_slru(void);
14821476

1483-
externvoidpgstat_count_slru_page_zeroed(SlruCtlctl);
1484-
externvoidpgstat_count_slru_page_hit(SlruCtlctl);
1485-
externvoidpgstat_count_slru_page_read(SlruCtlctl);
1486-
externvoidpgstat_count_slru_page_written(SlruCtlctl);
1487-
externvoidpgstat_count_slru_page_exists(SlruCtlctl);
1488-
externvoidpgstat_count_slru_flush(SlruCtlctl);
1489-
externvoidpgstat_count_slru_truncate(SlruCtlctl);
1490-
externchar*pgstat_slru_name(intidx);
1491-
externintpgstat_slru_index(constchar*name);
1477+
externvoidpgstat_count_slru_page_zeroed(intslru_idx);
1478+
externvoidpgstat_count_slru_page_hit(intslru_idx);
1479+
externvoidpgstat_count_slru_page_read(intslru_idx);
1480+
externvoidpgstat_count_slru_page_written(intslru_idx);
1481+
externvoidpgstat_count_slru_page_exists(intslru_idx);
1482+
externvoidpgstat_count_slru_flush(intslru_idx);
1483+
externvoidpgstat_count_slru_truncate(intslru_idx);
1484+
externconstchar*pgstat_slru_name(intslru_idx);
1485+
externintpgstat_slru_index(constchar*name);
14921486

14931487
#endif/* PGSTAT_H */

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