Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commitfb3dbdf

Browse files
committed
Rethink prior patch to filter out dead backend entries from the pgstats
file. The original code probed the PGPROC array separately for each PID,which was not good for large numbers of backends: not only is the runtimeO(N^2) but most of it is spent holding ProcArrayLock. Instead, take thelock just once and copy the active PIDs into an array, then use qsortand bsearch so that the lookup time is more like O(N log N).
1 parent4ce6be4 commitfb3dbdf

File tree

3 files changed

+64
-7
lines changed

3 files changed

+64
-7
lines changed

‎src/backend/postmaster/pgstat.c

Lines changed: 25 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -13,7 +13,7 @@
1313
*
1414
*Copyright (c) 2001-2005, PostgreSQL Global Development Group
1515
*
16-
*$PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.112 2005/11/22 18:17:17 momjian Exp $
16+
*$PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.113 2005/12/16 04:03:40 tgl Exp $
1717
* ----------
1818
*/
1919
#include"postgres.h"
@@ -2453,6 +2453,16 @@ pgstat_write_statsfile(void)
24532453
}
24542454
}
24552455

2456+
/*
2457+
* qsort/bsearch comparison routine for PIDs
2458+
*
2459+
* We assume PIDs are nonnegative, so there's no overflow risk
2460+
*/
2461+
staticint
2462+
comparePids(constvoid*v1,constvoid*v2)
2463+
{
2464+
return*((constint*)v1)-*((constint*)v2);
2465+
}
24562466

24572467
/* ----------
24582468
* pgstat_read_statsfile() -
@@ -2478,7 +2488,7 @@ pgstat_read_statsfile(HTAB **dbhash, Oid onlydb,
24782488
intmaxbackends=0;
24792489
inthavebackends=0;
24802490
boolfound;
2481-
boolcheck_pids;
2491+
int*live_pids;
24822492
MemoryContextuse_mcxt;
24832493
intmcxt_flags;
24842494

@@ -2497,13 +2507,17 @@ pgstat_read_statsfile(HTAB **dbhash, Oid onlydb,
24972507
{
24982508
use_mcxt=NULL;
24992509
mcxt_flags=0;
2500-
check_pids=false;
2510+
live_pids=NULL;
25012511
}
25022512
else
25032513
{
25042514
use_mcxt=TopTransactionContext;
25052515
mcxt_flags=HASH_CONTEXT;
2506-
check_pids= true;
2516+
live_pids=GetAllBackendPids();
2517+
/* Sort the PID array so we can use bsearch */
2518+
if (live_pids[0]>1)
2519+
qsort((void*)&live_pids[1],live_pids[0],sizeof(int),
2520+
comparePids);
25072521
}
25082522

25092523
/*
@@ -2706,7 +2720,13 @@ pgstat_read_statsfile(HTAB **dbhash, Oid onlydb,
27062720
/*
27072721
* If possible, check PID to verify still running
27082722
*/
2709-
if (check_pids&& !IsBackendPid(beentry->procpid))
2723+
if (live_pids&&
2724+
(live_pids[0]==0||
2725+
bsearch((void*)&beentry->procpid,
2726+
(void*)&live_pids[1],
2727+
live_pids[0],
2728+
sizeof(int),
2729+
comparePids)==NULL))
27102730
{
27112731
/*
27122732
* Note: we could send a BETERM message to tell the

‎src/backend/storage/ipc/procarray.c

Lines changed: 37 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -23,7 +23,7 @@
2323
*
2424
*
2525
* IDENTIFICATION
26-
* $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.9 2005/12/11 21:02:18 tgl Exp $
26+
* $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.10 2005/12/16 04:03:40 tgl Exp $
2727
*
2828
*-------------------------------------------------------------------------
2929
*/
@@ -732,6 +732,42 @@ IsBackendPid(int pid)
732732
return (BackendPidGetProc(pid)!=NULL);
733733
}
734734

735+
/*
736+
* GetAllBackendPids -- get an array of all current backends' PIDs
737+
*
738+
* The result is a palloc'd array with the number of active backends in
739+
* entry [0], their PIDs in entries [1] .. [n]. The caller must bear in
740+
* mind that the result may already be obsolete when returned.
741+
*/
742+
int*
743+
GetAllBackendPids(void)
744+
{
745+
int*result;
746+
intnpids;
747+
ProcArrayStruct*arrayP=procArray;
748+
intindex;
749+
750+
result= (int*)palloc((MaxBackends+1)*sizeof(int));
751+
npids=0;
752+
753+
LWLockAcquire(ProcArrayLock,LW_SHARED);
754+
755+
for (index=0;index<arrayP->numProcs;index++)
756+
{
757+
PGPROC*proc=arrayP->procs[index];
758+
759+
if (proc->pid!=0)/* ignore dummy procs */
760+
result[++npids]=proc->pid;
761+
}
762+
763+
LWLockRelease(ProcArrayLock);
764+
765+
Assert(npids <=MaxBackends);
766+
767+
result[0]=npids;
768+
returnresult;
769+
}
770+
735771
/*
736772
* CountActiveBackends --- count backends (other than myself) that are in
737773
*active transactions. This is used as a heuristic to decide if

‎src/include/storage/procarray.h

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/storage/procarray.h,v 1.6 2005/10/15 02:49:46 momjian Exp $
10+
* $PostgreSQL: pgsql/src/include/storage/procarray.h,v 1.7 2005/12/16 04:03:40 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -29,6 +29,7 @@ extern TransactionId GetOldestXmin(bool allDbs);
2929
externPGPROC*BackendPidGetProc(intpid);
3030
externintBackendXidGetPid(TransactionIdxid);
3131
externboolIsBackendPid(intpid);
32+
externint*GetAllBackendPids(void);
3233
externboolDatabaseHasActiveBackends(OiddatabaseId,boolignoreMyself);
3334

3435
externintCountActiveBackends(void);

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp