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Date: Fri, 5 Oct 2001 02:45:26 +0200
From: Andrea Arcangeli <andrea@suse.de>
To: Mike Kravetz <kravetz@us.ibm.com>
Cc: Linus Torvalds <torvalds@transmeta.com>, linux-kernel@vger.kernel.org
Subject: Re: Context switch times
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In-Reply-To: <20011004164102.E1245@w-mikek2.des.beaverton.ibm.com>; from kravetz@us.ibm.com on Thu, Oct 04, 2001 at 04:41:02PM -0700
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On Thu, Oct 04, 2001 at 04:41:02PM -0700, Mike Kravetz wrote:
> I know that running LMbench with 2 active tasks on an 8 CPU system
> results in those 2 tasks being 'round-robined' among all 8 CPUs.
> Prior analysis leads me to believe the reason for this is due to
> IPI latency.  reschedule_idle() chooses the 'best/correct' CPU for
> a task to run on, but before schedule() runs on that CPU another
> CPU runs schedule() and the result is that the task runs on a
> ?less desirable? CPU.  The nature of the LMbench scheduler benchmark

doesn't lmbench wakeup only via pipes? Linux uses the sync-wakeup that
avoids reschedule_idle in such case, to serialize the pipe load in the
same cpu.

Andrea
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