Received: from localhost (unknown [200.46.208.211]) by mail.postgresql.org (Postfix) with ESMTP id D5A4A6354DA for ; Fri, 13 Mar 2009 15:02:49 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by localhost (mx1.hub.org [200.46.208.211]) (amavisd-maia, port 10024) with ESMTP id 42857-03-4 for ; Fri, 13 Mar 2009 15:02:38 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from gwmta.wicourts.gov (gwmta.wicourts.gov [165.219.244.99]) by mail.postgresql.org (Postfix) with ESMTP id A2F8A634519 for ; Fri, 13 Mar 2009 15:02:37 -0300 (ADT) Received: from Courts-MTA by gwmta.wicourts.gov with Novell_GroupWise; Fri, 13 Mar 2009 13:02:36 -0500 Message-Id: <49BA5960.EE98.0025.0@wicourts.gov> X-Mailer: Novell GroupWise Internet Agent 7.0.3 Date: Fri, 13 Mar 2009 13:02:24 -0500 From: "Kevin Grittner" To: "Robert Haas" , "Tom Lane" Cc: "Greg Smith" , "pgsql-performance@postgresql.org" , "Scott Carey" , "Jignesh K. Shah" Subject: Re: Proposal of tunable fix for scalability of 8.4 References: <603c8f070903121829r31cf1472ha9876e5c480a542e@mail.gmail.com><603c8f070903121829r31cf1472ha9876e5c480a542e@mail.gmail.com> <12292.1236964604@sss.pgh.pa.us> In-Reply-To: <12292.1236964604@sss.pgh.pa.us> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Content-Disposition: inline X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200903/172 X-Sequence-Number: 33094 Tom Lane wrote: > Robert Haas writes: >> I think that changing the locking behavior is attacking the problem >> at the wrong level anyway. > > Right. By the time a patch here could have any effect, you've > already lost the game --- having to deschedule and reschedule a > process is a large cost compared to the typical lock hold time for > most LWLocks. So it would be better to look at how to avoid > blocking in the first place. That's what motivated my request for a profile of the "80 clients with zero wait" case. If all data access is in RAM, why can't 80 processes keep 64 threads (on 8 processors) busy? Does anybody else think that's an interesting question, or am I off in left field here? -Kevin