linux-kernel - Re: [PATCH] scheduler: fix x86 regression in native_sched

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Message-Id: <200712071629.31300.nickpiggin@yahoo.com.au>
Date:	Fri, 7 Dec 2007 16:29:30 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Stefano Brivio <stefano.brivio@...imi.it>
Cc:	Ingo Molnar <mingo@...e.hu>, Robert Love <rml@...h9.net>,
	linux-kernel@...r.kernel.org, Dave Jones <davej@...hat.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Michael Buesch <mb@...sch.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Len Brown <lenb@...nel.org>
Subject: Re: [PATCH] scheduler: fix x86 regression in native_sched_clock

On Friday 07 December 2007 12:19, Stefano Brivio wrote:
> This patch fixes a regression introduced by:
>
> commit bb29ab26863c022743143f27956cc0ca362f258c
> Author: Ingo Molnar <mingo@...e.hu>
> Date:   Mon Jul 9 18:51:59 2007 +0200
>
> This caused the jiffies counter to leap back and forth on cpufreq changes
> on my x86 box. I'd say that we can't always assume that TSC does "small
> errors" only, when marked unstable. On cpufreq changes these errors can be
> huge.
>
> The original bug report can be found here:
> http://bugzilla.kernel.org/show_bug.cgi?id=9475
>
>
> Signed-off-by: Stefano Brivio <stefano.brivio@...imi.it>

While your fix should probably go into 2.6.24...

This particular issue has aggravated me enough times. Let's
fix the damn thing properly already... I think what would work best
is a relatively simple change to the API along these lines:

View attachment "sched-clock.patch" of type "text/x-diff" (7825 bytes)