Received: from localhost (unknown [200.46.204.191]) by postgresql.org (Postfix) with ESMTP id A26892E30E3 for ; Thu, 3 Jan 2008 12:59:36 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.191]) (amavisd-maia, port 10024) with ESMTP id 70235-04 for ; Thu, 3 Jan 2008 12:59:33 -0400 (AST) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by postgresql.org (Postfix) with ESMTP id D0AEC2E313F for ; Thu, 3 Jan 2008 12:59:32 -0400 (AST) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.14.1/8.14.1) with ESMTP id m03GxUe8007084; Thu, 3 Jan 2008 11:59:30 -0500 (EST) To: Jakub Ouhrabka cc: pgsql-performance@postgresql.org Subject: Re: Linux/PostgreSQL scalability issue - problem with 8 cores In-reply-to: References: Comments: In-reply-to Jakub Ouhrabka message dated "Thu, 03 Jan 2008 12:50:01 +0100" Date: Thu, 03 Jan 2008 11:59:30 -0500 Message-ID: <7083.1199379570@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200801/7 X-Sequence-Number: 28246 Jakub Ouhrabka 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