Received: from localhost (unknown [200.46.204.187]) by postgresql.org (Postfix) with ESMTP id 758022E0344 for ; Wed, 26 Dec 2007 11:41:31 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.187]) (amavisd-maia, port 10024) with ESMTP id 70464-03 for ; Wed, 26 Dec 2007 11:41:08 -0400 (AST) Received: from wa-out-1112.google.com (wa-out-1112.google.com [209.85.146.177]) by postgresql.org (Postfix) with ESMTP id F3F8E2E0343 for ; Wed, 26 Dec 2007 11:41:25 -0400 (AST) Received: by wa-out-1112.google.com with SMTP id m38so4310451waf.5 for ; Wed, 26 Dec 2007 07:41:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; bh=9xVwM56vFxj0/mZYSGUeSfR/K0jSnLoWqGQGbKJlOnk=; b=rvkNv2FzBdXzuFAkQj2jpJAfuTMDQSx2O3l/CgCRBbK9j6oknXoiW0mRrj3M/ioeibDX3gZx5h9nX3DgRYFQ7J8tp7lgNMn7L0zcArvpOKY/nerf6AlOPgCU5tm2EwXsOctTykwhV4hJs0qBwfLkzvs/Sg4PKJE0JzUVUxGr8a4= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=Hl7D12Lza5/JX2VJN8Ii7SF1IHVrnVx/eS4x5CVeJNTzlwwDgdwP1knu7jCakZRPdVHbvc48b/JPPIUPOQcjX9LU/G7wCPzRtg+HNrr99aXSxR6IWXhHS9fqP24D+W+E//PPNWqJjayIUZb/jeLGuvOdyxDNGOkoUg0J3pENi6U= Received: by 10.115.76.1 with SMTP id d1mr6348330wal.108.1198683684305; Wed, 26 Dec 2007 07:41:24 -0800 (PST) Received: by 10.114.155.9 with HTTP; Wed, 26 Dec 2007 07:41:24 -0800 (PST) Message-ID: <1d4e0c10712260741w1f141fd6x2f482143d526ad48@mail.gmail.com> Date: Wed, 26 Dec 2007 16:41:24 +0100 From: "Guillaume Smet" To: "Simon Riggs" Subject: Re: More shared buffers causes lower performances Cc: pgsql-performance , "Stefan Kaltenbrunner" In-Reply-To: <1198668065.4221.288.camel@ebony.site> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <1d4e0c10712251606q6f9503deye3da4b68c51bf5e@mail.gmail.com> <1198668065.4221.288.camel@ebony.site> X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200712/359 X-Sequence-Number: 28175 On Dec 26, 2007 12:21 PM, Simon Riggs wrote: > bgwriter_lru_maxpages = 0 > > So we can see if the bgwriter has any hand in this? It doesn't change the behaviour I have. It's not checkpointing either as using pgbench-tools, I can see that tps and latency are quite stable during the entire run. Btw, thanks Greg for these nice tools. I thought it may be some sort of lock contention so I made a few tests with -N but I have the same behaviour. Then I decided to perform read-only tests using -S option (pgbench -S -s 100 -c 16 -t 30000 -U postgres bench). And still the same behaviour: shared_buffers=64MB : 20k tps shared_buffers=1024MB : 8k tps Any other idea? -- Guillaume