Messages in this thread | | | Date | Mon, 31 Jan 2011 20:24:00 +0100 | From | Jens Axboe <> | Subject | Re: [PATCH] blkio-throttle: Avoid calling blkiocg_lookup_group() for root group |
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On 2011-01-31 20:20, Jeff Moyer wrote: > Vivek Goyal <vgoyal@redhat.com> writes: > >> On Mon, Jan 17, 2011 at 04:56:06PM -0500, Vivek Goyal wrote: >>> o Jeff Moyer was doing some testing on a RAM backed disk and >>> blkiocg_lookup_group() showed up high overhead after memcpy(). Similarly >>> somebody else reported that blkiocg_lookup_group() is eating 6% extra >>> cpu. Though looking at the code I can't think why the overhead of >>> this function is so high. One thing is that it is called with very high >>> frequency (once for every IO). >>> >>> o For lot of folks blkio controller will be compiled in but they might >>> not have actually created cgroups. Hence optimize the case of root >>> cgroup where we can avoid calling blkiocg_lookup_group() if IO is happening >>> in root group (common case). >>> >>> Reported-by: Jeff Moyer <jmoyer@redhat.com> >>> Signed-off-by: Vivek Goyal <vgoyal@redhat.com> >> >> Hi Jens, >> >> Do you have any concerns regarding this patch? > > Acked-by: Jeff Moyer <jmoyer@redhat.com> > > Jens, this is a pretty easy performance regression fixup. I think it > should be pulled in sooner rather than later. We've also witnessed this > slowdown on big performance testing rigs, so it's not just a ramdisk > issue.
Yep, will fold it into 2.6.38, thanks!
-- Jens Axboe
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