From: Tom Lane <tgl@sss.pgh.pa.us>
To: Kelly Burkhart <kelly.burkhart@gmail.com>
Cc: Evgeny Gridasov <eugrid@fpm.kubsu.ru>
Cc: pgsql-performance@postgresql.org
Subject: Re: EXPLAIN ANALYZE on 8.2
Date: Thu, 14 Dec 2006 19:05:31 -0500
Message-ID: <29450.1166141131@sss.pgh.pa.us> (raw)
In-Reply-To: <fa1e4ce70612141543o8866d7fg417eca88ce9b1344@mail.gmail.com>
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>
<fa1e4ce70612141543o8866d7fg417eca88ce9b1344@mail.gmail.com>
"Kelly Burkhart" <kelly.burkhart@gmail.com> 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
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, kelly.burkhart@gmail.com, eugrid@fpm.kubsu.ru
Subject: Re: EXPLAIN ANALYZE on 8.2
In-Reply-To: <29450.1166141131@sss.pgh.pa.us>
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