| From: | "Steinar H(dot) Gunderson" <sgunderson(at)bigfoot(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Dave Held <dave(dot)held(at)arrayservicesgrp(dot)com>, Greg Stark <gsstark(at)mit(dot)edu>, John A Meinel <john(at)arbash-meinel(dot)com>, Magnus Hagander <mha(at)sollentuna(dot)net>, Ken Egervari <ken(at)upfactor(dot)com>, pgsql-performance(at)postgresql(dot)org, pgsql-hackers-win32(at)postgresql(dot)org |
| Subject: | Re: [PERFORM] Help with tuning this query (with |
| Date: | 2005-03-08 02:06:24 |
| Message-ID: | 20050308020624.GA753@uio.no |
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| Thread: | |
| Lists: | pgsql-hackers-win32 pgsql-performance |
On Mon, Mar 07, 2005 at 09:02:38PM -0500, Tom Lane wrote:
> One thought that was bothering me was that if the CPU goes idle while
> waiting for disk I/O, its clock might stop or slow down dramatically.
> If we believed such a counter for EXPLAIN, we'd severely understate
> the cost of disk I/O.
>
> I dunno if that is the case on any Windows hardware or not, but none
> of this thread is making me feel confident that we know what
> QueryPerformanceCounter does measure.
I believe the counter is actually good in such a situation -- I'm not a Win32
guru, but I believe it is by far the best timer for measuring, well,
performance of a process like this. After all, it's what it was designed to
be :-)
OBTW, I think I can name something like 15 or 20 different function calls to
measure time in the Win32 API (all of them in use); it really is a giant
mess.
/* Steinar */
--
Homepage: http://www.sesse.net/
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