X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (av.hub.org [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id C7DA3D7012 for ; Wed, 24 Aug 2005 02:07:39 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 33799-04 for ; Wed, 24 Aug 2005 05:07:34 +0000 (GMT) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by svr1.postgresql.org (Postfix) with ESMTP id C1D4ED6DC2 for ; Wed, 24 Aug 2005 02:07:32 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.13.1/8.13.1) with ESMTP id j7O57Mw2021393; Wed, 24 Aug 2005 01:07:22 -0400 (EDT) To: Gavin Sherry Cc: PFC , William Yu , pgsql-performance@postgresql.org Subject: Re: Caching by Postgres In-reply-to: References: <20050823171045.12112.qmail@web51309.mail.yahoo.com> <20050823124323.710a9dd3.frank@wiles.org> <430B6DE3.6040109@sun.com> Comments: In-reply-to Gavin Sherry message dated "Wed, 24 Aug 2005 14:38:02 +1000" Date: Wed, 24 Aug 2005 01:07:22 -0400 Message-ID: <21392.1124860042@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.006 required=5 tests=[AWL=0.006] X-Spam-Level: X-Archive-Number: 200508/372 X-Sequence-Number: 14119 Gavin Sherry writes: > A filesystem could, in theory, help us by providing an API which allows us > to tell the file system either: the way we'd like it to read ahead, the > fact that we don't want it to read ahead or the way we'd like it to cache > (or not cache) data. The thing is, most OSes provide interfaces to do this > already and we make only little use of them (I'm think of > madv_sequential(), madv_random(), POSIX fadvise(), the various flags to > open() which AIX, HPUX, Solaris provide). Yeah ... the main reason we've not spent too much time on that sort of stuff is that *it's not portable*. And with all due respect to Hans, special tweaks for one filesystem are even less interesting than special tweaks for one OS. regards, tom lane