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

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Date:	Sat, 16 Jun 2007 18:51:29 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	malc <av1474@...tv.ru>
CC:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Dmitry Adamushko <dmitry.adamushko@...il.com>
Subject: Re: [patch] sched: accurate user accounting

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.

>>
>> Could you provide more details on the APC tool that you are using -- I
>> do not understand the orange and yellow lines, do they represent system
>> and user time?
> 
> It's somewhat documented on the page: http://www.boblycat.org/~malc/apc
> Anyway the left bar is based on information from `/proc/stat' the right
> one is derived from the kernel module that just times how much time was
> spent in idle handler. The graphs: red - `/proc/stat', yellow - module.
> 
>> NOTE: There is some inconsistency in the values reported by /usr/bin/time
>> (getrusage) and values reported in /proc or through delay accounting.
> 
> I don't really use `getrusage'.
> 

Tools like /usr/bin/time do.

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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