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

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Date:	Sat, 16 Jun 2007 18:07:41 +0400 (MSD)
From:	malc <av1474@...tv.ru>
To:	Balbir Singh <balbir@...ux.vnet.ibm.com>
cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Dmitry Adamushko <dmitry.adamushko@...il.com>
Subject: Re: [patch] sched: accurate user accounting

On Sat, 16 Jun 2007, Balbir Singh wrote:

> malc wrote:
>> On Fri, 15 Jun 2007, Balbir Singh wrote:
>>
>>> malc wrote:
>>>> On Thu, 14 Jun 2007, Ingo Molnar wrote:
>>>>
>>
>> [..snip..]
>>
>>>>
>>>> Now integral load matches the one obtained via the "accurate" method.
>>>> However the report for individual cores are of by around 20% percent.
>>>>
>>>
>>> I think I missed some of the context, is the accounting of individual
>>> tasks
>>> or cpustat values off by 20%? I'll try and reproduce this problem.
>>
>> Neither actually, the individual core idle times reported via `/proc/stat'
>> are off by 20 percent, one over estimates and the other under estimates
>> and the sum is right on the mark.
>>
>
> Interesting, the idle time accounting (done from account_system_time())
> has not changed. Has your .config changed? Could you please send
> it across. I've downloaded apc and I am trying to reproduce your problem.

http://www.boblycat.org/~malc/apc/cfs/ has config for 2.6.21 an the 
diff against 2.6.21.4-cfs-v16.

I updated hog (can be found in the above directory) to call setitimer
with a bit saner values (apprantly tickless has profound effect on
itimers interface). While fooling around with this version of hog
on 2.6.21.4-cfs-v16 i stumbled upon rather strange behavior (the
screenshot is also at the address above, note that kernel was booted
with maxcpus=1)

[..snip..]

-- 
vale
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