From: Tom Lane <tgl@sss.pgh.pa.us>
To: Jakub Ouhrabka <kuba@comgate.cz>
Cc: pgsql-performance@postgresql.org
Subject: Re: Linux/PostgreSQL scalability issue - problem with 8 cores
Date: Thu, 03 Jan 2008 11:59:30 -0500
Message-ID: <7083.1199379570@sss.pgh.pa.us> (raw)
In-Reply-To: <flii57$748$1@news.hub.org>
References: <flii57$748$1@news.hub.org>
Jakub Ouhrabka <kuba@comgate.cz> writes:
> we have a PostgreSQL dedicated Linux server with 8 cores (2xX5355). We
> came accross a strange issue: when running with all 8 cores enabled
> approximatly once a minute (period differs) the system is very busy for
> a few seconds (~5-10s) and we don't know why - this issue don't show up
> when we tell Linux to use only 2 cores, with 4 cores the problem is here
> but it is still better than with 8 cores - all on the same machine, same
> config, same workload. We don't see any apparent reason for these peaks.
Interesting. Maybe you could use oprofile to try to see what's
happening? It sounds a bit like momentary contention for a spinlock,
but exactly what isn't clear.
> Can this be connected with our heavy use of listen/notify and hundreds
> backends in listen mode?
Perhaps. Have you tried logging executions of NOTIFY to see if they are
correlated with the spikes?
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, kuba@comgate.cz
Subject: Re: Linux/PostgreSQL scalability issue - problem with 8 cores
In-Reply-To: <7083.1199379570@sss.pgh.pa.us>
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