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Date: Thu, 8 Nov 2001 17:33:58 +0100 (CET)
From: Ingo Molnar <mingo@elte.hu>
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To: "M. Edward Borasky" <znmeb@aracnet.com>
Cc: <linux-kernel@vger.kernel.org>
Subject: RE: [patch] scheduler cache affinity improvement for 2.4 kernels
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On Thu, 8 Nov 2001, M. Edward Borasky wrote:

> I can think of some circumstances where one would want the *opposite*
> of this patch. Consider a "time-sharing" system running both
> CPU-intensive "batch" tasks and "interactive" tasks. There is going to
> be a tradeoff between efficiency / throughput of the batch tasks and
> the response times of interactive ones. [...]

this mechanizm is already part of the scheduler and is not affected by my
patch. Interactive tasks get their '->counter' value increased gradually
via the recalculate code in the scheduler, which after some time gives
them effective priority above that of CPU-intensive processes.

To see this mechanizm working, just boot into the stock kernel or try a
kernel with the patch applied, start a few CPU-intensive processes, eg.
a couple of subshells doing an infinite loop:

	while N=1; do N=1; done &
	while N=1; do N=1; done &
	while N=1; do N=1; done &
	while N=1; do N=1; done &

and see how the interactive shell is still responding instantaneously in
such a mixed workload, despite having the same static priority as the
subshells.

	Ingo

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