Re: Context switching and Xeon processors - Mailing list pgsql-performance

From Tom Lane
Subject Re: Context switching and Xeon processors
Date
Msg-id 16608.1133905013@sss.pgh.pa.us
Whole thread Raw
In response to Context switching and Xeon processors  ("Brandon Metcalf" <bmetcalf@nortel.com>)
Responses Re: Context switching and Xeon processors  ("Brandon Metcalf" <bmetcalf@nortel.com>)
List pgsql-performance
"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

pgsql-performance by date:

Previous
From: Tom Lane
Date:
Subject: Re: Missed index opportunity for outer join?
Next
From: Rory Campbell-Lange
Date:
Subject: Re: LVM and Postgres