linux-kernel - Re: [PATCH -tip 1/4] sched: Avoid cputime scaling overflow

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Message-ID: <20130430111119.GA28821@gmail.com>
Date:	Tue, 30 Apr 2013 13:11:19 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Stanislaw Gruszka <sgruszka@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>, hpa@...or.com,
	rostedt@...dmis.org, akpm@...ux-foundation.org, tglx@...utronix.de,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Dave Hansen <dave@...1.net>
Subject: Re: [PATCH -tip 1/4] sched: Avoid cputime scaling overflow


* Stanislaw Gruszka <sgruszka@...hat.com> wrote:

> Here is patch, which add Linus cputime scaling algorithm to the kernel.
> 
> This is follow up of commit d9a3c9823a2e6a543eb7807fb3d15d8233817ec5
> "sched: Lower chances of cputime scaling overflow" which try to avoid
> multiplication overflow, but not guarantee that the overflow will not
> happen.
> 
> Linus crated different algorithm, which avoid completely multiplication
> overflow by dropping precision when numbers are big. It was tested
> by me and it gives good relative error of scaled numbers.
> 
> Signed-off-by: Stanislaw Gruszka <sgruszka@...hat.com>

For multi-authored code it's generally nice to add a tag like this:

   Originally-From: Linus Torvalds <torvalds@...ux-foundation.org>

It would also be nice to quote the testing results/output and the 
precision estimations in the changelog - so that others can see the code's 
current capabilities and limitations.

Thanks,

	Ingo
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