From owner-freebsd-smp  Mon Jul  2 12:58:48 2001
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Date: Mon, 2 Jul 2001 14:24:17 -0700 (PDT)
From: Julian Elischer <julian@elischer.org>
To: Alfred Perlstein <bright@sneakerz.org>
Cc: "Michael C . Wu" <keichii@peorth.iteration.net>,
	"E.B. Dreger" <eddy+public+spam@noc.everquick.net>, smp@FreeBSD.ORG
Subject: Re: per cpu runqueues, cpu affinity and cpu binding.
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On Mon, 2 Jul 2001, Alfred Perlstein wrote:

> * Julian Elischer <julian@elischer.org> [010702 13:38] wrote:
> > 
> > At USENIX we decided to proceed with the KSE work.
> 
> yay!
> 
> > 
> > As a side issue I plan on NOT ALLOWING multiple KSEs (thread carriers?)
> > from the same thread group in the same process to be on the same
> > processor. SO load balancing and processor affinity will not
> > apply to the thread-carrying entities (KSEs). Of course the userland
> > thread scheduler has the ultimate say as to which processor
> > a thread is scheduled on.
> 
> Actually, this may cause some performance problems, when you have
> a shared address space you can avoid tlb shootdowns when a process's
> address space changes, you also share the cache, lastly there's
> some rumor about a new CPU archetecture that runs multple threads
> on the same CPU at the same time.  Just food for thought.

If you select to run 2 thread carriers (see other mail on nomenclature)> 
(KSEs) then you have specifically asked for 2 processors worth of
concurrency so we ASSUME you know what you are doing.. If you want to run 
all the threads on a single processor to get better cache activity, then
you should't ASK to run on 2  (or more) processors.

:-)




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