[PATCH 01/10] Documentation

Gui Jianfeng guijianfeng at cn.fujitsu.com
Wed Mar 18 00:23:29 PDT 2009

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

Gui Jianfeng

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