Hi Ming Lei,
On Fri, Jan 17, 2014 at 06:56:24PM +0800, Ming Lei wrote:
> Hi Fengguang,
>
> On Fri, Jan 17, 2014 at 6:20 PM, Fengguang Wu <fengguang...@intel.com> wrote:
> > Ming Lei,
> >
> > We noticed that commit 74e72f894 ("lib/percpu_counter.c: fix
> > __percpu_counter_add()") introduces -47.6% regression in aim7 brk_test
> > on a 2S SNB server. Comparing to its parent commit:
>
> The commit has a bug, could you apply Hugh's patch[1] to test if
> the regression can be fixed?
>
> If the performance regression is still there, it may be caused by bad
> performance of this_cpu_add(), then I suggest you to test the patch[2]
> too without enabling lockdep.
>
>
> [1], http://marc.info/?t=138991497900001&r=1&w=2
Hugh's patch is enough to fix the kernel oops and performance regressions:
74e72f894d56eb9 0ddc13035a9b3679a0e1a2cec
--------------- -------------------------
1 ~ 0% -100.0% 0
vpx/micro/xfstests/4HDD-ext4-generic-slow2
1 ~ 0% -100.0% 0 TOTAL
dmesg.This_should_not_happen_Data_will_be_lost
74e72f894d56eb9 0ddc13035a9b3679a0e1a2cec
--------------- -------------------------
71965 ~ 0% +90.4% 137038 ~ 0% lkp-snb01/micro/aim7/brk_test
71965 ~ 0% +90.4% 137038 ~ 0% TOTAL aim7.2000.jobs-per-min
In fact it turns regression to noticeable performance increase. :)
Thanks,
Fengguang
> [2], http://marc.info/?l=linux-kernel&m=138909074202090&w=2
>
> Thanks,
> --
> Ming Lei
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