Re: Time sliced CFQ io scheduler

Prakash K. Cheemplavam
2004-12-03T09:37:42Z

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Jens Axboe schrieb:
> On Fri, Dec 03 2004, Prakash K. Cheemplavam wrote:
>
>>Jens Axboe schrieb:
>>
>>>On Thu, Dec 02 2004, Prakash K. Cheemplavam wrote:
>>>
>>
>>>>0 3 3080 2208 1156 817712 0 0 3592 75624 1326 2289 1 36
>>>>0 63
>>>>0 3 3080 2664 1156 818240 0 0 5124 15692 1302 992 1 18
>>>>0 81
>>>>0 3 3080 2580 1160 815832 0 0 4356 155792 1375 1064 1 39
>>>>0 60
>>>>0 3 3080 2472 1160 817124 0 0 3076 100852 1345 1138 1 23
>>>>0 76
>>>>2 4 3080 2836 1148 816228 0 0 3336 100412 1352 1379 1 47
>>>>0 52
>>>>0 4 3080 2708 1144 815964 0 0 3844 48908 1343 871 1 25
>>>>0 74
>>>>0 3 3080 2748 1152 815984 0 0 3332 71996 1338 843 1 27
>>>>0 72
>>>
>>>
>>>Can you try with the patch that is in the parent of this thread? The
>>>above doesn't look that bad, although read performance could be better
>>>of course. But try with the patch please, I'm sure it should help you
>>>quite a lot.
>>>
>>
>>It actually got worse: Though the read rate seems accepteble, it is not, as
>>interactivity is dead while writing. I cannot start porgrammes, other
>>programmes which want to do i/o pretty much hang. This is only while
>>writing. While reading there is no such problem.
>
>
> Interesting, thanks for testing. I'll run some tests here as well, so
> far only the cases mentioned yesterday have been tested.

BTW, in case it is misread: Above (except the io performance as such) is
no regression: The other schedulers behave the same on my system.

> You could try and bumb the slice period. But I'll experiment and see
> what happens. What is your test case?

[slice bumping] Uhm, is it doable via proc? I haven't seen text docs to
your patch and I am not good at kernel code ;-)

My test case was apkm's one: write 1gb continuesly and try to cat a
several gb big file to /dev/null. At the same time I checked starting
other apps/using my emial client...

For me the problem in mainline has been since quite some time...checked
till kernel 2.6.7.

Prakash

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