From: Achilleas Mantzios <achill@matrix.gatewaynet.com>
Organization: Dynacom Tankers Mgmt
To: Tom Lane <tgl@sss.pgh.pa.us>
Subject: Re: syslog performance when logging big statements
Date: Tue, 8 Jul 2008 18:21:57 +0300
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Cc: pgsql-performance@postgresql.org
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	<8675.1215527716@sss.pgh.pa.us>
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=CE=A3=CF=84=CE=B9=CF=82 Tuesday 08 July 2008 17:35:16 =CE=BF/=CE=B7 Tom La=
ne =CE=AD=CE=B3=CF=81=CE=B1=CF=88=CE=B5:
> 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=3Don, the same st=
atement needs 15 seconds to return.
>=20
> 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?
>=20
> 			regards, tom lane
>=20

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.

=2D-=20
Achilleas Mantzios