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Commitb5498a2

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Add some optional code (conditionally compiled under #ifdef LWLOCK_STATS)
to track the number of LWLock acquisitions and the number of times weblock waiting for an LWLock, on a per-process basis. After having neededthis twice in the past few months, seems like it should go into CVS.
1 parentefe2222 commitb5498a2

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‎src/backend/storage/lmgr/lwlock.c

Lines changed: 58 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -15,7 +15,7 @@
1515
* Portions Copyright (c) 1994, Regents of the University of California
1616
*
1717
* IDENTIFICATION
18-
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lwlock.c,v 1.38 2006/03/05 15:58:39 momjian Exp $
18+
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lwlock.c,v 1.39 2006/04/21 16:45:12 tgl Exp $
1919
*
2020
*-------------------------------------------------------------------------
2121
*/
@@ -25,6 +25,7 @@
2525
#include"access/multixact.h"
2626
#include"access/subtrans.h"
2727
#include"miscadmin.h"
28+
#include"storage/ipc.h"
2829
#include"storage/lwlock.h"
2930
#include"storage/proc.h"
3031
#include"storage/spin.h"
@@ -84,6 +85,13 @@ NON_EXEC_STATIC LWLockPadded *LWLockArray = NULL;
8485
staticintnum_held_lwlocks=0;
8586
staticLWLockIdheld_lwlocks[MAX_SIMUL_LWLOCKS];
8687

88+
#ifdefLWLOCK_STATS
89+
staticintcounts_for_pid=0;
90+
staticint*sh_acquire_counts;
91+
staticint*ex_acquire_counts;
92+
staticint*block_counts;
93+
#endif
94+
8795

8896
#ifdefLOCK_DEBUG
8997
boolTrace_lwlocks= false;
@@ -109,6 +117,31 @@ LOG_LWDEBUG(const char *where, LWLockId lockid, const char *msg)
109117
#defineLOG_LWDEBUG(a,b,c)
110118
#endif/* LOCK_DEBUG */
111119

120+
#ifdefLWLOCK_STATS
121+
122+
staticvoid
123+
print_lwlock_stats(intcode,Datumarg)
124+
{
125+
inti;
126+
int*LWLockCounter= (int*) ((char*)LWLockArray-2*sizeof(int));
127+
intnumLocks=LWLockCounter[1];
128+
129+
/* Grab an LWLock to keep different backends from mixing reports */
130+
LWLockAcquire(0,LW_EXCLUSIVE);
131+
132+
for (i=0;i<numLocks;i++)
133+
{
134+
if (sh_acquire_counts[i]||ex_acquire_counts[i]||block_counts[i])
135+
fprintf(stderr,"PID %d lwlock %d: shacq %u exacq %u blk %u\n",
136+
MyProcPid,i,sh_acquire_counts[i],ex_acquire_counts[i],
137+
block_counts[i]);
138+
}
139+
140+
LWLockRelease(0);
141+
}
142+
143+
#endif/* LWLOCK_STATS */
144+
112145

113146
/*
114147
* Compute number of LWLocks to allocate.
@@ -263,6 +296,26 @@ LWLockAcquire(LWLockId lockid, LWLockMode mode)
263296

264297
PRINT_LWDEBUG("LWLockAcquire",lockid,lock);
265298

299+
#ifdefLWLOCK_STATS
300+
/* Set up local count state first time through in a given process */
301+
if (counts_for_pid!=MyProcPid)
302+
{
303+
int*LWLockCounter= (int*) ((char*)LWLockArray-2*sizeof(int));
304+
intnumLocks=LWLockCounter[1];
305+
306+
sh_acquire_counts=calloc(numLocks,sizeof(int));
307+
ex_acquire_counts=calloc(numLocks,sizeof(int));
308+
block_counts=calloc(numLocks,sizeof(int));
309+
counts_for_pid=MyProcPid;
310+
on_shmem_exit(print_lwlock_stats,0);
311+
}
312+
/* Count lock acquisition attempts */
313+
if (mode==LW_EXCLUSIVE)
314+
ex_acquire_counts[lockid]++;
315+
else
316+
sh_acquire_counts[lockid]++;
317+
#endif/* LWLOCK_STATS */
318+
266319
/*
267320
* We can't wait if we haven't got a PGPROC. This should only occur
268321
* during bootstrap or shared memory initialization. Put an Assert here
@@ -369,6 +422,10 @@ LWLockAcquire(LWLockId lockid, LWLockMode mode)
369422
*/
370423
LOG_LWDEBUG("LWLockAcquire",lockid,"waiting");
371424

425+
#ifdefLWLOCK_STATS
426+
block_counts[lockid]++;
427+
#endif
428+
372429
for (;;)
373430
{
374431
/* "false" means cannot accept cancel/die interrupt here. */

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