Re: [LKP] [sched/numa] a43455a1d57: +94.1% proc-vmstat.numa_hint_faults_local
From: Rik van Riel
Date: Wed Jul 30 2014 - 10:26:25 EST
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
>> 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):
> 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.
I will run the same thing here with SPECjbb2005.
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