Messages in this thread | | | Date | Mon, 31 Jan 2011 20:25:27 +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 20:24, Jens Axboe wrote: > 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!
Just to be clear, it's queued up in for-linus so it will go to 2.6.38 on the next push. It was updated last week, this is what it has so far:
Sergey Senozhatsky (1): loop: queue_lock NULL pointer derefence in blk_throtl_exit
Stephen M. Cameron (1): cciss: make cciss_revalidate not loop through CISS_MAX_LUNS volumes unnecessarily.
Tao Ma (1): blktrace: Don't output messages if NOTIFY isn't set.
Tracey Dent (2): drivers/block/Makefile: replace the use of <module>-objs with <module>-y drivers/block/aoe/Makefile: replace the use of <module>-objs with <module>-y
Vivek Goyal (2): cfq: rename a function to give it more appropriate name blkio-throttle: Avoid calling blkiocg_lookup_group() for root group
block/blk-throttle.c | 10 +++++++++- block/cfq-iosched.c | 6 +++--- drivers/block/Makefile | 2 +- drivers/block/aoe/Makefile | 2 +- drivers/block/cciss.c | 2 +- drivers/block/loop.c | 3 +++ kernel/trace/blktrace.c | 7 +++++++ 7 files changed, 25 insertions(+), 7 deletions(-)
-- Jens Axboe
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