Re: Excessive context switching on SMP Xeons

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
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