Messages in this thread |  | | | Date | Fri, 3 Dec 2004 10:43:14 +0100 | | From | Jens Axboe <> | | Subject | Re: Time sliced CFQ io scheduler |
On Fri, Dec 03 2004, Prakash K. Cheemplavam wrote: > 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.
Yes, that's what I assumed. Another thing to keep in mind is that even with just a single writer, you could have 3 people doing writeout for you (pdflush for each disk, and the writer itself), while the reader is on its own. This could affect latencies/bandwidth for the reader in not-so pleasant ways.
> >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 ;-)
:-)
See my previous mail, it tells you how to do it.
-- Jens Axboe
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