Messages in this thread |  | | | Date | Tue, 13 May 2008 14:58:53 +0200 | | From | Matthew <> | | Subject | Re: performance "regression" in cfq compared to anticipatory, deadline and noop |
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On Tue, May 13, 2008 at 2:20 PM, Jens Axboe <jens.axboe@oracle.com> wrote: > > On Sun, May 11 2008, Kasper Sandberg wrote: > > On Sun, 2008-05-11 at 14:14 +0100, Daniel J Blueman wrote: > > > I've been experiencing this for a while also; an almost 50% regression > > > is seen for single-process reads (ie sync) if slice_idle is 1ms or > > > more (eg default of 8) [1], which seems phenomenal. > > > > > > Jens, is this the expected price to pay for optimal busy-spindle > > > scheduling, a design issue, bug or am I missing something totally? > > > > > > Thanks, > > > Daniel [snip] ... [snip] > > > > Thisd would appear to be quite a considerable performance difference. > > Indeed, that is of course a bug. The initial mail here mentions this as > a regression - which kernel was the last that worked ok? > > If someone would send me a blktrace of such a slow run, that would be > nice. Basically just do a blktrace /dev/sda (or whatever device) while > doing the hdparm, preferably storing output files on a difference > device. Then send the raw sda.blktrace.* files to me. Thanks! > > -- > Jens Axboe > >
Hi Jens,
I called this a "regression" since I wasn't sure if this is a real bug or just something introduced recently, I just started to use cfq as main io-scheduler so I can't tell ...
testing 2.6.17 unfortunately is somewhat impossible for me (reiser4; too new hardware - problems with jmicron)
google "says" that it seemingly already existed since at least 2.6.18 (Ubuntu DapperDrake) [see: http://ubuntuforums.org/showpost.php?p=1484633&postcount=12]
well - back to topic:
for a blktrace one need to enable CONFIG_BLK_DEV_IO_TRACE , right ? blktrace can be obtained from your git-repo ?
Thanks
Mat
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