From 398b240151708d7e971631875760ddbad3a63e0e Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sat, 12 May 2012 19:21:54 -0400 Subject: [PATCH] Avoid unnecessary process wakeups in the log collector. syslogger was coded to wake up once per second whether there was anything useful to do or not. As part of our campaign to reduce the server's idle power consumption, change it to use a latch for waiting. Now, in the absence of any data to log or any signals to service, it will only wake up at the programmed logfile rotation times (if any). --- src/backend/postmaster/syslogger.c | 95 +++++++++++++++++++++--------- 1 file changed, 66 insertions(+), 29 deletions(-) diff --git a/src/backend/postmaster/syslogger.c b/src/backend/postmaster/syslogger.c index f5ae84157c..3528879243 100644 --- a/src/backend/postmaster/syslogger.c +++ b/src/backend/postmaster/syslogger.c @@ -9,8 +9,7 @@ * in postgresql.conf. If these limits are reached or passed, the * current logfile is closed and a new one is created (rotated). * The logfiles are stored in a subdirectory (configurable in - * postgresql.conf), using an internal naming scheme that mangles - * creation time and current postmaster pid. + * postgresql.conf), using a user-selectable naming scheme. * * Author: Andreas Pflug * @@ -40,6 +39,7 @@ #include "postmaster/postmaster.h" #include "postmaster/syslogger.h" #include "storage/ipc.h" +#include "storage/latch.h" #include "storage/pg_shmem.h" #include "utils/guc.h" #include "utils/ps_status.h" @@ -93,6 +93,7 @@ static FILE *syslogFile = NULL; static FILE *csvlogFile = NULL; static char *last_file_name = NULL; static char *last_csv_file_name = NULL; +static Latch sysLoggerLatch; /* * Buffers for saving partial messages from different backends. @@ -168,12 +169,14 @@ SysLoggerMain(int argc, char *argv[]) char *currentLogDir; char *currentLogFilename; int currentLogRotationAge; + pg_time_t now; IsUnderPostmaster = true; /* we are a postmaster subprocess now */ MyProcPid = getpid(); /* reset MyProcPid */ MyStartTime = time(NULL); /* set our start time in case we call elog */ + now = MyStartTime; #ifdef EXEC_BACKEND syslogger_parseArgs(argc, argv); @@ -246,6 +249,9 @@ SysLoggerMain(int argc, char *argv[]) elog(FATAL, "setsid() failed: %m"); #endif + /* Initialize private latch for use by signal handlers */ + InitLatch(&sysLoggerLatch); + /* * Properly accept or ignore signals the postmaster might send us * @@ -296,14 +302,19 @@ SysLoggerMain(int argc, char *argv[]) { bool time_based_rotation = false; int size_rotation_for = 0; + long cur_timeout; + int cur_flags; #ifndef WIN32 - int bytesRead; int rc; - fd_set rfds; - struct timeval timeout; #endif + /* Clear any already-pending wakeups */ + ResetLatch(&sysLoggerLatch); + + /* + * Process any requests or signals received recently. + */ if (got_SIGHUP) { got_SIGHUP = false; @@ -353,11 +364,10 @@ SysLoggerMain(int argc, char *argv[]) } } - if (!rotation_requested && Log_RotationAge > 0 && !rotation_disabled) + if (Log_RotationAge > 0 && !rotation_disabled) { /* Do a logfile rotation if it's time */ - pg_time_t now = (pg_time_t) time(NULL); - + now = (pg_time_t) time(NULL); if (now >= next_rotation_time) rotation_requested = time_based_rotation = true; } @@ -389,28 +399,40 @@ SysLoggerMain(int argc, char *argv[]) logfile_rotate(time_based_rotation, size_rotation_for); } -#ifndef WIN32 - /* - * Wait for some data, timing out after 1 second + * Calculate time till next time-based rotation, so that we don't + * sleep longer than that. We assume the value of "now" obtained + * above is still close enough. Note we can't make this calculation + * until after calling logfile_rotate(), since it will advance + * next_rotation_time. */ - FD_ZERO(&rfds); - FD_SET(syslogPipe[0], &rfds); - - timeout.tv_sec = 1; - timeout.tv_usec = 0; - - rc = select(syslogPipe[0] + 1, &rfds, NULL, NULL, &timeout); - - if (rc < 0) + if (Log_RotationAge > 0 && !rotation_disabled) { - if (errno != EINTR) - ereport(LOG, - (errcode_for_socket_access(), - errmsg("select() failed in logger process: %m"))); + if (now < next_rotation_time) + cur_timeout = (next_rotation_time - now) * 1000L; /* msec */ + else + cur_timeout = 0; + cur_flags = WL_TIMEOUT; } - else if (rc > 0 && FD_ISSET(syslogPipe[0], &rfds)) + else { + cur_timeout = -1L; + cur_flags = 0; + } + + /* + * Sleep until there's something to do + */ +#ifndef WIN32 + rc = WaitLatchOrSocket(&sysLoggerLatch, + WL_LATCH_SET | WL_SOCKET_READABLE | cur_flags, + syslogPipe[0], + cur_timeout); + + if (rc & WL_SOCKET_READABLE) + { + int bytesRead; + bytesRead = read(syslogPipe[0], logbuffer + bytes_in_logbuffer, sizeof(logbuffer) - bytes_in_logbuffer); @@ -445,8 +467,8 @@ SysLoggerMain(int argc, char *argv[]) /* * On Windows we leave it to a separate thread to transfer data and - * detect pipe EOF. The main thread just wakes up once a second to - * check for SIGHUP and rotation conditions. + * detect pipe EOF. The main thread just wakes up to handle SIGHUP + * and rotation conditions. * * Server code isn't generally thread-safe, so we ensure that only one * of the threads is active at a time by entering the critical section @@ -454,7 +476,9 @@ SysLoggerMain(int argc, char *argv[]) */ LeaveCriticalSection(&sysloggerSection); - pg_usleep(1000000L); + (void) WaitLatch(&sysLoggerLatch, + WL_LATCH_SET | cur_flags, + cur_timeout); EnterCriticalSection(&sysloggerSection); #endif /* WIN32 */ @@ -957,7 +981,7 @@ write_syslogger_file(const char *buffer, int count, int destination) /* * Worker thread to transfer data from the pipe to the current logfile. * - * We need this because on Windows, WaitForSingleObject does not work on + * We need this because on Windows, WaitforMultipleObjects does not work on * unnamed pipes: it always reports "signaled", so the blocking ReadFile won't * allow for SIGHUP; and select is for sockets only. */ @@ -1010,6 +1034,9 @@ pipeThread(void *arg) /* if there's any data left then force it out now */ flush_pipe_input(logbuffer, &bytes_in_logbuffer); + /* set the latch to waken the main thread, which will quit */ + SetLatch(&sysLoggerLatch); + LeaveCriticalSection(&sysloggerSection); _endthread(); return 0; @@ -1285,12 +1312,22 @@ set_next_rotation_time(void) static void sigHupHandler(SIGNAL_ARGS) { + int save_errno = errno; + got_SIGHUP = true; + SetLatch(&sysLoggerLatch); + + errno = save_errno; } /* SIGUSR1: set flag to rotate logfile */ static void sigUsr1Handler(SIGNAL_ARGS) { + int save_errno = errno; + rotation_requested = true; + SetLatch(&sysLoggerLatch); + + errno = save_errno; } -- 2.40.0