Re: stats collector process high CPU utilization

Sorry, I introduced this bug.

---------------------------------------------------------------------------

Tom Lane wrote:
> Benjamin Minshall  writes:
> > Tom Lane wrote:
> >> It's sounding like what you had was just transient bloat, in which case
> >> it might be useful to inquire whether anything out-of-the-ordinary had
> >> been done to the database right before the excessive-CPU-usage problem
> >> started.
> 
> > I don't believe that there was any unusual activity on the server, but I 
> > have set up some more detailed logging to hopefully identify a pattern 
> > if the problem resurfaces.
> 
> A further report led us to realize that 8.2.x in fact has a nasty bug
> here: the stats collector is supposed to dump its stats to a file at
> most every 500 milliseconds, but the code was actually waiting only
> 500 microseconds :-(.  The larger the stats file, the more obvious
> this problem gets.
> 
> If you want to patch this before 8.2.4, try this...
> 
> Index: pgstat.c
> ===================================================================
> RCS file: /cvsroot/pgsql/src/backend/postmaster/pgstat.c,v
> retrieving revision 1.140.2.2
> diff -c -r1.140.2.2 pgstat.c
> *** pgstat.c	26 Jan 2007 20:07:01 -0000	1.140.2.2
> --- pgstat.c	1 Mar 2007 20:04:50 -0000
> ***************
> *** 1689,1695 ****
>   	/* Preset the delay between status file writes */
>   	MemSet(&write_timeout, 0, sizeof(struct itimerval));
>   	write_timeout.it_value.tv_sec = PGSTAT_STAT_INTERVAL / 1000;
> ! 	write_timeout.it_value.tv_usec = PGSTAT_STAT_INTERVAL % 1000;
>   
>   	/*
>   	 * Read in an existing statistics stats file or initialize the stats to
> --- 1689,1695 ----
>   	/* Preset the delay between status file writes */
>   	MemSet(&write_timeout, 0, sizeof(struct itimerval));
>   	write_timeout.it_value.tv_sec = PGSTAT_STAT_INTERVAL / 1000;
> ! 	write_timeout.it_value.tv_usec = (PGSTAT_STAT_INTERVAL % 1000) * 1000;
>   
>   	/*
>   	 * Read in an existing statistics stats file or initialize the stats to
> 
> 
> 			regards, tom lane
> 
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-- 
  Bruce Momjian            http://momjian.us
  EnterpriseDB                               http://www.enterprisedb.com

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