Re: [LKP] [sched/numa] a43455a1d57: +94.1% proc-vmstat.numa_hint_faults_local
From: Aaron Lu
Date: Thu Jul 31 2014 - 01:05:05 EST
On Wed, Jul 30, 2014 at 10:25:03AM -0400, Rik van Riel wrote:
> On 07/29/2014 10:14 PM, Aaron Lu wrote:
> > On Tue, Jul 29, 2014 at 04:04:37PM -0400, Rik van Riel wrote:
> >> On Tue, 29 Jul 2014 10:17:12 +0200
> >> Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> >>>> +#define NUMA_SCALE 1000
> >>>> +#define NUMA_MOVE_THRESH 50
> >>> Please make that 1024, there's no reason not to use power of two here.
> >>> This base 10 factor thing annoyed me no end already, its time for it to
> >>> die.
> >> That's easy enough. However, it would be good to know whether
> >> this actually helps with the regression Aaron found :)
> > Sorry for the delay.
> > I applied the last patch and queued the hackbench job to the ivb42 test
> > machine for it to run 5 times, and here is the result(regarding the
> > proc-vmstat.numa_hint_faults_local field):
> > 173565
> > 201262
> > 192317
> > 198342
> > 198595
> > avg:
> > 192816
> > It seems it is still very big than previous kernels.
> It looks like a step in the right direction, though.
> Could you try running with a larger threshold?
> >> +++ b/kernel/sched/fair.c
> >> @@ -924,10 +924,12 @@ static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
> >> /*
> >> * These return the fraction of accesses done by a particular task, or
> >> - * task group, on a particular numa node. The group weight is given a
> >> - * larger multiplier, in order to group tasks together that are almost
> >> - * evenly spread out between numa nodes.
> >> + * task group, on a particular numa node. The NUMA move threshold
> >> + * prevents task moves with marginal improvement, and is set to 5%.
> >> */
> >> +#define NUMA_SCALE 1024
> >> +#define NUMA_MOVE_THRESH (5 * NUMA_SCALE / 100)
> It would be good to see if changing NUMA_MOVE_THRESH to
> (NUMA_SCALE / 8) does the trick.
With your 2nd patch and the above change, the result is:
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