Bill,
In order to manifest the context switch problem you will definitely
require clients to be set to more than one in pgbench. It only occurs
when 2 or more backends need access to shared memory.
If you want help backpatching Gavin's patch I'll be glad to do it for
you, but you do need a recent kernel.
Dave
On Thu, 2004-10-07 at 14:48, Bill Montgomery wrote:
> Michael Adler wrote:
>
> >On Thu, Oct 07, 2004 at 11:48:41AM -0400, Bill Montgomery wrote:
> >
> >
> >>Alan Stange wrote:
> >>
> >>The same test on a Dell PowerEdge 1750, Dual Xeon 3.2 GHz, 512k cache,
> >>HT on, Linux 2.4.21-20.ELsmp (RHEL 3), 4GB memory, pg 7.4.5:
> >>
> >>Far less performance that the Dual Opterons with a low number of
> >>clients, but the gap narrows as the number of clients goes up. Anyone
> >>smarter than me care to explain?
> >>
> >>
> >
> >You'll have to wait for someone smarter than you, but I will posit
> >this: Did you use a tmpfs filesystem like Alan? You didn't mention
> >either way. Alan did that as an attempt remove IO as a variable.
> >
> >-Mike
> >
> >
>
> Yes, I should have been more explicit. My goal was to replicate his
> experiment as closely as possible in my environment, so I did run my
> postgres data directory on a tmpfs.
>
> -Bill Montgomery
>
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--
Dave Cramer
519 939 0336
ICQ # 14675561
www.postgresintl.com
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