linux-kernel - Re: [patch] sched: avoid div in rebalance

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Message-ID: <20070112095940.0795a998@localhost.localdomain>
Date:	Fri, 12 Jan 2007 09:59:40 +0000
From:	Alan <alan@...rguk.ukuu.org.uk>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Andrew Morton <akpm@...l.org>, Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [patch] sched: avoid div in rebalance_tick

On Fri, 12 Jan 2007 07:02:13 +0100
Nick Piggin <npiggin@...e.de> wrote:

> Just noticed this while looking at a bug.
> Avoid an expensive integer divide 3 times per CPU per tick.

Integer divide is cheap on some modern processors, and multibit shift
isn't on all embedded ones.

How about putting back scale = 1 and using

scale += scale;

instead of the shift and getting what ought to be even better results

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