Use setitimer() for stats file write, rather than do a gettimeofday()

call for every stats packet read to adjust select() timeout.  Other
stylistic improvements.

diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 39f7f3e74646e975448815ef6d11ba239080e34e..ef27046e95cdf01b30b709f9ef8de1263a4fa5fa 100644 (file)
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -13,7 +13,7 @@
  *
  *     Copyright (c) 2001-2005, PostgreSQL Global Development Group
  *
- *     $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.116 2006/01/02 00:58:00 momjian Exp $
+ *     $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.117 2006/01/03 16:42:17 momjian Exp $
  * ----------
  */
 #include "postgres.h"
@@ -117,7 +117,7 @@ static time_t last_pgstat_start_time;
 
 static long pgStatNumMessages = 0;
 
-static bool pgStatRunningInCollector = FALSE;
+static bool pgStatRunningInCollector = false;
 
 /*
  * Place where backends store per-table info to be sent to the collector.
@@ -145,6 +145,7 @@ static HTAB *pgStatBeDead = NULL;
 static PgStat_StatBeEntry *pgStatBeTable = NULL;
 static int     pgStatNumBackends = 0;
 
+static volatile bool   need_statwrite;
 
 /* ----------
  * Local function forward declarations
@@ -164,6 +165,7 @@ static void pgstat_parseArgs(int argc, char *argv[]);
 
 NON_EXEC_STATIC void PgstatBufferMain(int argc, char *argv[]);
 NON_EXEC_STATIC void PgstatCollectorMain(int argc, char *argv[]);
+static void force_statwrite(SIGNAL_ARGS);
 static void pgstat_recvbuffer(void);
 static void pgstat_exit(SIGNAL_ARGS);
 static void pgstat_die(SIGNAL_ARGS);
@@ -1548,13 +1550,11 @@ PgstatCollectorMain(int argc, char *argv[])
        PgStat_Msg      msg;
        fd_set          rfds;
        int                     readPipe;
-       int                     nready;
        int                     len = 0;
-       struct timeval timeout;
-       struct timeval next_statwrite;
-       bool            need_statwrite;
+       struct itimerval timeval;
        HASHCTL         hash_ctl;
-
+       bool            need_timer = false;
+       
        MyProcPid = getpid();           /* reset MyProcPid */
 
        /*
@@ -1572,7 +1572,7 @@ PgstatCollectorMain(int argc, char *argv[])
        /* kluge to allow buffer process to kill collector; FIXME */
        pqsignal(SIGQUIT, pgstat_exit);
 #endif
-       pqsignal(SIGALRM, SIG_IGN);
+       pqsignal(SIGALRM, force_statwrite);
        pqsignal(SIGPIPE, SIG_IGN);
        pqsignal(SIGUSR1, SIG_IGN);
        pqsignal(SIGUSR2, SIG_IGN);
@@ -1597,17 +1597,17 @@ PgstatCollectorMain(int argc, char *argv[])
        init_ps_display("stats collector process", "", "");
        set_ps_display("");
 
-       /*
-        * Arrange to write the initial status file right away
-        */
-       gettimeofday(&next_statwrite, NULL);
-       need_statwrite = TRUE;
+       need_statwrite = true;
+
+       MemSet(&timeval, 0, sizeof(struct itimerval));
+       timeval.it_value.tv_sec = PGSTAT_STAT_INTERVAL / 1000;
+       timeval.it_value.tv_usec = PGSTAT_STAT_INTERVAL % 1000;
 
        /*
         * Read in an existing statistics stats file or initialize the stats to
         * zero.
         */
-       pgStatRunningInCollector = TRUE;
+       pgStatRunningInCollector = true;
        pgstat_read_statsfile(&pgStatDBHash, InvalidOid, NULL, NULL);
 
        /*
@@ -1634,34 +1634,11 @@ PgstatCollectorMain(int argc, char *argv[])
         */
        for (;;)
        {
-               /*
-                * If we need to write the status file again (there have been changes
-                * in the statistics since we wrote it last) calculate the timeout
-                * until we have to do so.
-                */
                if (need_statwrite)
                {
-                       struct timeval now;
-
-                       gettimeofday(&now, NULL);
-                       /* avoid assuming that tv_sec is signed */
-                       if (now.tv_sec > next_statwrite.tv_sec ||
-                               (now.tv_sec == next_statwrite.tv_sec &&
-                                now.tv_usec >= next_statwrite.tv_usec))
-                       {
-                               timeout.tv_sec = 0;
-                               timeout.tv_usec = 0;
-                       }
-                       else
-                       {
-                               timeout.tv_sec = next_statwrite.tv_sec - now.tv_sec;
-                               timeout.tv_usec = next_statwrite.tv_usec - now.tv_usec;
-                               if (timeout.tv_usec < 0)
-                               {
-                                       timeout.tv_sec--;
-                                       timeout.tv_usec += 1000000;
-                               }
-                       }
+                       pgstat_write_statsfile();
+                       need_statwrite = false;
+                       need_timer = true;
                }
 
                /*
@@ -1673,9 +1650,7 @@ PgstatCollectorMain(int argc, char *argv[])
                /*
                 * Now wait for something to do.
                 */
-               nready = select(readPipe + 1, &rfds, NULL, NULL,
-                                               (need_statwrite) ? &timeout : NULL);
-               if (nready < 0)
+               if (select(readPipe + 1, &rfds, NULL, NULL, NULL) < 0)
                {
                        if (errno == EINTR)
                                continue;
@@ -1684,18 +1659,6 @@ PgstatCollectorMain(int argc, char *argv[])
                                         errmsg("select() failed in statistics collector: %m")));
                }
 
-               /*
-                * If there are no descriptors ready, our timeout for writing the
-                * stats file happened.
-                */
-               if (nready == 0)
-               {
-                       pgstat_write_statsfile();
-                       need_statwrite = FALSE;
-
-                       continue;
-               }
-
                /*
                 * Check if there is a new statistics message to collect.
                 */
@@ -1813,17 +1776,12 @@ PgstatCollectorMain(int argc, char *argv[])
                         */
                        pgStatNumMessages++;
 
-                       /*
-                        * If this is the first message after we wrote the stats file the
-                        * last time, setup the timeout that it'd be written.
-                        */
-                       if (!need_statwrite)
+                       if (need_timer)
                        {
-                               gettimeofday(&next_statwrite, NULL);
-                               next_statwrite.tv_usec += ((PGSTAT_STAT_INTERVAL) * 1000);
-                               next_statwrite.tv_sec += (next_statwrite.tv_usec / 1000000);
-                               next_statwrite.tv_usec %= 1000000;
-                               need_statwrite = TRUE;
+                               if (setitimer(ITIMER_REAL, &timeval, NULL))
+                                       ereport(ERROR,
+                                                 (errmsg("unable to set statistics collector timer: %m")));
+                               need_timer = false;
                        }
                }
 
@@ -1848,6 +1806,13 @@ PgstatCollectorMain(int argc, char *argv[])
 }
 
 
+static void
+force_statwrite(SIGNAL_ARGS)
+{
+       need_statwrite = true;
+}
+
+
 /* ----------
  * pgstat_recvbuffer() -
  *
@@ -1865,7 +1830,6 @@ pgstat_recvbuffer(void)
        struct timeval timeout;
        int                     writePipe = pgStatPipe[1];
        int                     maxfd;
-       int                     nready;
        int                     len;
        int                     xfr;
        int                     frm;
@@ -1906,6 +1870,14 @@ pgstat_recvbuffer(void)
         */
        msgbuffer = (char *) palloc(PGSTAT_RECVBUFFERSZ);
 
+       /*
+        * Wait for some work to do; but not for more than 10 seconds. (This
+        * determines how quickly we will shut down after an ungraceful
+        * postmaster termination; so it needn't be very fast.)
+        */
+       timeout.tv_sec = 10;
+       timeout.tv_usec = 0;
+
        /*
         * Loop forever
         */
@@ -1946,16 +1918,7 @@ pgstat_recvbuffer(void)
                                maxfd = writePipe;
                }
 
-               /*
-                * Wait for some work to do; but not for more than 10 seconds. (This
-                * determines how quickly we will shut down after an ungraceful
-                * postmaster termination; so it needn't be very fast.)
-                */
-               timeout.tv_sec = 10;
-               timeout.tv_usec = 0;
-
-               nready = select(maxfd + 1, &rfds, &wfds, NULL, &timeout);
-               if (nready < 0)
+               if (select(maxfd + 1, &rfds, &wfds, NULL, &timeout) < 0)
                {
                        if (errno == EINTR)
                                continue;