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List:       freebsd-stable
Subject:    Re: MFC pthreads before 3.2 is released?
From:       Mike Meyer <mwm () phone ! net>
Date:       1999-04-28 21:58:51
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On Wed, 28 Apr 1999, Tom wrote:
>   It doesn't really depend on postgresql at all.  If your process mix is
> cpu intensive, you will get a benefit.  If your process mix is
> kernel/syscall intensive, then you won't get much benefit as only one
> process can be active in the kernel at a time.  Now, are your postgresql
> processes cpu or kernel intensive?  Depends on what you do.

That I believe - that's why I listed the other things going on.  The
note on the Postgres list is what made me stop to think about
this. The claim there was that postgres - in a syscall intensive app -
actually *slowed down* with the second processor enabled. I've seen
similar effects elsewhere. Early versions of Ultrix turned up better
numbers on multiuser benchmarks if you turned one processor off. In
practice - in that environment - someones long-running number-cruncher
grabbed the second processor pretty quickly, having pretty much the
same effect as disabling it. Since they wind up getting faster
real-time turnaround off the 8820 than they did of the Cray X/MP-14,
everyone was happy.

The real question isn't how much benefit I'll see - it's whether or
not there are job mixes that will cause the system to seem slower.

	<mike




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