Received: from localhost (maia-3.hub.org [200.46.204.184]) by postgresql.org (Postfix) with ESMTP id 982A99FA1FD for ; Thu, 14 Dec 2006 20:05:45 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.184]) (amavisd-new, port 10024) with ESMTP id 54461-05 for ; Thu, 14 Dec 2006 20:05:36 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey-1.7.4 Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by postgresql.org (Postfix) with ESMTP id E18049FA173 for ; Thu, 14 Dec 2006 20:05:40 -0400 (AST) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.13.6/8.13.6) with ESMTP id kBF05VM7029451; Thu, 14 Dec 2006 19:05:31 -0500 (EST) To: "Kelly Burkhart" cc: "Evgeny Gridasov" , pgsql-performance@postgresql.org Subject: Re: EXPLAIN ANALYZE on 8.2 In-reply-to: References: <20061214163230.d46f0138.eugrid@fpm.kubsu.ru> <21146.1166112702@sss.pgh.pa.us> <20061214192920.c75385d6.eugrid@fpm.kubsu.ru> <21516.1166114475@sss.pgh.pa.us> Comments: In-reply-to "Kelly Burkhart" message dated "Thu, 14 Dec 2006 17:43:51 -0600" Date: Thu, 14 Dec 2006 19:05:31 -0500 Message-ID: <29450.1166141131@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200612/392 X-Sequence-Number: 22448 "Kelly Burkhart" writes: > I hope this isn't a "crummy mainboard" but I can't seem to affect > things by changing clock source (kernel 2.6.16 SLES10). I tried > kernel command option clock=XXX where XXX in > (cyclone,hpet,pmtmr,tsc,pit), no option was significantly better than > the default. I believe that on machines where gettimeofday is really nice and fast, it doesn't require entry to the kernel at all; there's some hack that makes the clock readable from userspace. (Obviously a switch to kernel mode would set you back a lot of the cycles involved here.) So it's not so much the kernel that you need to teach as glibc. How you do that is beyond my expertise, but maybe that will help you google for the right thing ... regards, tom lane