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Commit398b240

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Avoid unnecessary process wakeups in the log collector.
syslogger was coded to wake up once per second whether there was anythinguseful to do or not. As part of our campaign to reduce the server's idlepower consumption, change it to use a latch for waiting. Now, in theabsence of any data to log or any signals to service, it will only wake upat the programmed logfile rotation times (if any).
1 parent7b85527 commit398b240

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1 file changed

+66
-29
lines changed

1 file changed

+66
-29
lines changed

‎src/backend/postmaster/syslogger.c‎

Lines changed: 66 additions & 29 deletions
Original file line numberDiff line numberDiff line change
@@ -9,8 +9,7 @@
99
* in postgresql.conf. If these limits are reached or passed, the
1010
* current logfile is closed and a new one is created (rotated).
1111
* The logfiles are stored in a subdirectory (configurable in
12-
* postgresql.conf), using an internal naming scheme that mangles
13-
* creation time and current postmaster pid.
12+
* postgresql.conf), using a user-selectable naming scheme.
1413
*
1514
* Author: Andreas Pflug <pgadmin@pse-consulting.de>
1615
*
@@ -40,6 +39,7 @@
4039
#include"postmaster/postmaster.h"
4140
#include"postmaster/syslogger.h"
4241
#include"storage/ipc.h"
42+
#include"storage/latch.h"
4343
#include"storage/pg_shmem.h"
4444
#include"utils/guc.h"
4545
#include"utils/ps_status.h"
@@ -93,6 +93,7 @@ static FILE *syslogFile = NULL;
9393
staticFILE*csvlogFile=NULL;
9494
staticchar*last_file_name=NULL;
9595
staticchar*last_csv_file_name=NULL;
96+
staticLatchsysLoggerLatch;
9697

9798
/*
9899
* Buffers for saving partial messages from different backends.
@@ -168,12 +169,14 @@ SysLoggerMain(int argc, char *argv[])
168169
char*currentLogDir;
169170
char*currentLogFilename;
170171
intcurrentLogRotationAge;
172+
pg_time_tnow;
171173

172174
IsUnderPostmaster= true;/* we are a postmaster subprocess now */
173175

174176
MyProcPid=getpid();/* reset MyProcPid */
175177

176178
MyStartTime=time(NULL);/* set our start time in case we call elog */
179+
now=MyStartTime;
177180

178181
#ifdefEXEC_BACKEND
179182
syslogger_parseArgs(argc,argv);
@@ -246,6 +249,9 @@ SysLoggerMain(int argc, char *argv[])
246249
elog(FATAL,"setsid() failed: %m");
247250
#endif
248251

252+
/* Initialize private latch for use by signal handlers */
253+
InitLatch(&sysLoggerLatch);
254+
249255
/*
250256
* Properly accept or ignore signals the postmaster might send us
251257
*
@@ -296,14 +302,19 @@ SysLoggerMain(int argc, char *argv[])
296302
{
297303
booltime_based_rotation= false;
298304
intsize_rotation_for=0;
305+
longcur_timeout;
306+
intcur_flags;
299307

300308
#ifndefWIN32
301-
intbytesRead;
302309
intrc;
303-
fd_setrfds;
304-
structtimevaltimeout;
305310
#endif
306311

312+
/* Clear any already-pending wakeups */
313+
ResetLatch(&sysLoggerLatch);
314+
315+
/*
316+
* Process any requests or signals received recently.
317+
*/
307318
if (got_SIGHUP)
308319
{
309320
got_SIGHUP= false;
@@ -353,11 +364,10 @@ SysLoggerMain(int argc, char *argv[])
353364
}
354365
}
355366

356-
if (!rotation_requested&&Log_RotationAge>0&& !rotation_disabled)
367+
if (Log_RotationAge>0&& !rotation_disabled)
357368
{
358369
/* Do a logfile rotation if it's time */
359-
pg_time_tnow= (pg_time_t)time(NULL);
360-
370+
now= (pg_time_t)time(NULL);
361371
if (now >=next_rotation_time)
362372
rotation_requested=time_based_rotation= true;
363373
}
@@ -389,28 +399,40 @@ SysLoggerMain(int argc, char *argv[])
389399
logfile_rotate(time_based_rotation,size_rotation_for);
390400
}
391401

392-
#ifndefWIN32
393-
394402
/*
395-
* Wait for some data, timing out after 1 second
403+
* Calculate time till next time-based rotation, so that we don't
404+
* sleep longer than that. We assume the value of "now" obtained
405+
* above is still close enough. Note we can't make this calculation
406+
* until after calling logfile_rotate(), since it will advance
407+
* next_rotation_time.
396408
*/
397-
FD_ZERO(&rfds);
398-
FD_SET(syslogPipe[0],&rfds);
399-
400-
timeout.tv_sec=1;
401-
timeout.tv_usec=0;
402-
403-
rc=select(syslogPipe[0]+1,&rfds,NULL,NULL,&timeout);
404-
405-
if (rc<0)
409+
if (Log_RotationAge>0&& !rotation_disabled)
406410
{
407-
if (errno!=EINTR)
408-
ereport(LOG,
409-
(errcode_for_socket_access(),
410-
errmsg("select() failed in logger process: %m")));
411+
if (now<next_rotation_time)
412+
cur_timeout= (next_rotation_time-now)*1000L;/* msec */
413+
else
414+
cur_timeout=0;
415+
cur_flags=WL_TIMEOUT;
411416
}
412-
elseif (rc>0&&FD_ISSET(syslogPipe[0],&rfds))
417+
else
413418
{
419+
cur_timeout=-1L;
420+
cur_flags=0;
421+
}
422+
423+
/*
424+
* Sleep until there's something to do
425+
*/
426+
#ifndefWIN32
427+
rc=WaitLatchOrSocket(&sysLoggerLatch,
428+
WL_LATCH_SET |WL_SOCKET_READABLE |cur_flags,
429+
syslogPipe[0],
430+
cur_timeout);
431+
432+
if (rc&WL_SOCKET_READABLE)
433+
{
434+
intbytesRead;
435+
414436
bytesRead=read(syslogPipe[0],
415437
logbuffer+bytes_in_logbuffer,
416438
sizeof(logbuffer)-bytes_in_logbuffer);
@@ -445,16 +467,18 @@ SysLoggerMain(int argc, char *argv[])
445467

446468
/*
447469
* On Windows we leave it to a separate thread to transfer data and
448-
* detect pipe EOF. The main thread just wakes uponce a second to
449-
*check for SIGHUPand rotation conditions.
470+
* detect pipe EOF. The main thread just wakes upto handle SIGHUP
471+
* and rotation conditions.
450472
*
451473
* Server code isn't generally thread-safe, so we ensure that only one
452474
* of the threads is active at a time by entering the critical section
453475
* whenever we're not sleeping.
454476
*/
455477
LeaveCriticalSection(&sysloggerSection);
456478

457-
pg_usleep(1000000L);
479+
(void)WaitLatch(&sysLoggerLatch,
480+
WL_LATCH_SET |cur_flags,
481+
cur_timeout);
458482

459483
EnterCriticalSection(&sysloggerSection);
460484
#endif/* WIN32 */
@@ -957,7 +981,7 @@ write_syslogger_file(const char *buffer, int count, int destination)
957981
/*
958982
* Worker thread to transfer data from the pipe to the current logfile.
959983
*
960-
* We need this because on Windows,WaitForSingleObject does not work on
984+
* We need this because on Windows,WaitforMultipleObjects does not work on
961985
* unnamed pipes: it always reports "signaled", so the blocking ReadFile won't
962986
* allow for SIGHUP; and select is for sockets only.
963987
*/
@@ -1010,6 +1034,9 @@ pipeThread(void *arg)
10101034
/* if there's any data left then force it out now */
10111035
flush_pipe_input(logbuffer,&bytes_in_logbuffer);
10121036

1037+
/* set the latch to waken the main thread, which will quit */
1038+
SetLatch(&sysLoggerLatch);
1039+
10131040
LeaveCriticalSection(&sysloggerSection);
10141041
_endthread();
10151042
return0;
@@ -1285,12 +1312,22 @@ set_next_rotation_time(void)
12851312
staticvoid
12861313
sigHupHandler(SIGNAL_ARGS)
12871314
{
1315+
intsave_errno=errno;
1316+
12881317
got_SIGHUP= true;
1318+
SetLatch(&sysLoggerLatch);
1319+
1320+
errno=save_errno;
12891321
}
12901322

12911323
/* SIGUSR1: set flag to rotate logfile */
12921324
staticvoid
12931325
sigUsr1Handler(SIGNAL_ARGS)
12941326
{
1327+
intsave_errno=errno;
1328+
12951329
rotation_requested= true;
1330+
SetLatch(&sysLoggerLatch);
1331+
1332+
errno=save_errno;
12961333
}

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