From: Tom Lane <tgl@sss.pgh.pa.us>
To: Brandon Metcalf <bmetcalf@nortel.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Context switching and Xeon processors
Date: Tue, 06 Dec 2005 16:36:53 -0500
Message-ID: <16608.1133905013@sss.pgh.pa.us> (raw)
In-Reply-To: <Pine.LNX.4.58L.0512061454010.1468@cash.rhiamet.com>
References: <Pine.LNX.4.58L.0512061454010.1468@cash.rhiamet.com>
"Brandon Metcalf" <bmetcalf@nortel.com> writes:
> We've been tuning the kernel (2.4 SMP flavor) and have improved
> performance quite a bit. I'm now wondering if turning off HT will
> improve performance even more. Based on the vmstat output below, is
> the context switching typical or too high?
Given that your CPU usage is hovering around 2%, it's highly unlikely
that you'll be able to measure any change at all by fiddling with HT.
What you need to be working on is disk I/O --- the "80% wait" number
is what should be getting your attention, not the CS number.
(FWIW, on the sort of hardware you're talking about, I wouldn't worry
about CS rates lower than maybe 10000/sec --- the hardware can sustain
well over 10x that.)
regards, tom lane
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, bmetcalf@nortel.com
Subject: Re: Context switching and Xeon processors
In-Reply-To: <16608.1133905013@sss.pgh.pa.us>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox