linux-kernel - Re: [PATCH 01/10] Documentation

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Date:	Wed, 18 Mar 2009 15:23:29 +0800
From:	Gui Jianfeng <guijianfeng@...fujitsu.com>
To:	Vivek Goyal <vgoyal@...hat.com>
CC:	Dhaval Giani <dhaval@...ux.vnet.ibm.com>, nauman@...gle.com,
	dpshah@...gle.com, lizf@...fujitsu.com, mikew@...gle.com,
	fchecconi@...il.com, paolo.valente@...more.it,
	jens.axboe@...cle.com, ryov@...inux.co.jp,
	fernando@...ellilink.co.jp, s-uchida@...jp.nec.com,
	taka@...inux.co.jp, arozansk@...hat.com, jmoyer@...hat.com,
	oz-kernel@...hat.com, balbir@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, akpm@...ux-foundation.org,
	menage@...gle.com, peterz@...radead.org
Subject: Re: [PATCH 01/10] Documentation

Vivek Goyal wrote:
>> Hi Vivek,
>>
>> I would be interested in knowing if these are the results expected?
>>
> 
> Hi Dhaval, 
> 
> Good question. Keeping current expectation in mind, yes these are expected
> results. To begin with, current expectations are that try to emulate
> cfq behavior and the kind of service differentiation we get between
> threads of different priority, same kind of service differentiation we
> should get from different cgroups.
>  
> Having said that, in theory a more accurate estimate should be amount 
> of actual disk time a queue/cgroup got. I have put a tracing message
> to keep track of total service received by a queue. If you run "blktrace"
> then you can see that. Ideally, total service received by two threads
> over a period of time should be in same proportion as their cgroup
> weights.
> 
> It will not be easy to achive it given the constraints we have got in
> terms of how to accurately we can account for disk time actually used by a
> queue in certain situations. So to begin with I am targetting that
> try to meet same kind of service differentation between cgroups as
> cfq provides between threads and then slowly refine it to see how
> close one can come to get accurate numbers in terms of "total_serivce"
> received by each queue.

  Hi Vivek,

  I simply tested with blktrace opened. I create two groups and set ioprio
  4 and 7 respectively(the corresponding weight should 4:1, right?), and 
  start two dd concurrently. UUIC, Ideally, the proportion of service two 
  dd got should be 4:1 in a period of time when they are running. I extract 
  *served* value from blktrace output and sum them up. I found the proportion 
  of the sum of *served* value is about 1.7:1
  Am i missing something?

  I extract the following highlight value
  8,0  0   0   18.914906549     0  m   N 6601ioq served=*0x13* total service=0x184d

> 
> Thanks
> Vivek
> 
> 
> 

-- 
Regards
Gui Jianfeng

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