linux-kernel - Re: [patch] sched: accurate user accounting

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Message-ID: <Pine.LNX.4.64.0703251521270.11555@linmac.oyster.ru>
Date:	Sun, 25 Mar 2007 15:34:48 +0400 (MSD)
From:	malc <av1474@...tv.ru>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Con Kolivas <kernel@...ivas.org>,
	linux list <linux-kernel@...r.kernel.org>, zwane@...radead.org,
	ck list <ck@....kolivas.org>, ijuz@...nheim.wgermanyrulez.de,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch] sched: accurate user accounting

On Sun, 25 Mar 2007, Ingo Molnar wrote:

>
> * Con Kolivas <kernel@...ivas.org> wrote:
>
>> For an rsdl 0.33 patched kernel. Comments? Overhead worth it?
>
> we want to do this - and we should do this to the vanilla scheduler
> first and check the results. I've back-merged the patch to before RSDL
> and have tested it - find the patch below. Vale, could you try this
> patch against a 2.6.21-rc4-ish kernel and re-test your testcase?

[..snip..]

Compilation failed with:
kernel/built-in.o(.sched.text+0x564): more undefined references to `__udivdi3' follow

$ gcc --version | head -1
gcc (GCC) 3.4.6

$ cat /proc/cpuinfo | grep cpu
cpu             : 7447A, altivec supported

Can't say i really understand why 64bit arithmetics suddenly became an
issue here.

Am i supposed to run the testcase and see if numbers in `/proc/stat'
now match the reality closer? To be really accurate `/proc/stat'
should be left alone methinks, because no matter how good you try the
fundamential fact that time(and consequently load percentage) is not
really devided in USER_HZ intervals will interfere with ones quest for
accurate statistics. (Wonder what this patch will do to slightly modified
hog that produced this: http://www.boblycat.org/~malc/apc/load-c2d-hog.png
but this will have to wait till i get to the PC at work)

-- 
vale (this is not name/nick/alias, this is latin for farewell)
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