From: Achilleas Mantzios <achill@matrix.gatewaynet.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@postgresql.org
Subject: Re: syslog performance when logging big statements
Date: Tue, 8 Jul 2008 18:21:57 +0300
Message-ID: <200807081821.57935.achill@matrix.gatewaynet.com> (raw)
In-Reply-To: <8675.1215527716@sss.pgh.pa.us>
References: <200807081524.47366.achill@matrix.gatewaynet.com>
<8675.1215527716@sss.pgh.pa.us>
Στις Tuesday 08 July 2008 17:35:16 ο/η Tom Lane έγραψε:
> Achilleas Mantzios <achill@matrix.gatewaynet.com> writes:
> > In this case, the INSERT *needs* 20 minutes to return. This is because the logging through syslog seems to severely slow the system.
> > If instead, i use stderr, even with logging_collector=on, the same statement needs 15 seconds to return.
>
> Hmm. There's a function in elog.c that breaks log messages into chunks
> for syslog. I don't think anyone's ever looked hard at its performance
> --- maybe there's an O(N^2) behavior?
>
> regards, tom lane
>
Thanx,
i changed PG_SYSLOG_LIMIT in elog.c:1269 from 128 to 1048576
#ifndef PG_SYSLOG_LIMIT
/* #define PG_SYSLOG_LIMIT 128 */
#define PG_SYSLOG_LIMIT 1048576
#endif
and i got super fast stderr performance. :)
However, i noticed a certain amount of data in the log is lost.
Didnt dig much to the details tho.
--
Achilleas Mantzios
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Subject: Re: syslog performance when logging big statements
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