Re: [PATCH v2 3/5] mm: enlarge NUMA counters threshold size

From: kemi
Date: Wed Dec 20 2017 - 05:23:48 EST

On 2017å12æ20æ 18:12, Michal Hocko wrote:
> On Wed 20-12-17 13:52:14, kemi wrote:
>> On 2017å12æ19æ 20:40, Michal Hocko wrote:
>>> On Tue 19-12-17 14:39:24, Kemi Wang wrote:
>>>> We have seen significant overhead in cache bouncing caused by NUMA counters
>>>> update in multi-threaded page allocation. See 'commit 1d90ca897cb0 ("mm:
>>>> update NUMA counter threshold size")' for more details.
>>>> This patch updates NUMA counters to a fixed size of (MAX_S16 - 2) and deals
>>>> with global counter update using different threshold size for node page
>>>> stats.
>>> Again, no numbers.
>> Compare to vanilla kernel, I don't think it has performance improvement, so
>> I didn't post performance data here.
>> But, if you would like to see performance gain from enlarging threshold size
>> for NUMA stats (compare to the first patch), I will do that later.
> Please do. I would also like to hear _why_ all counters cannot simply
> behave same. In other words why we cannot simply increase
> stat_threshold? Maybe calculate_normal_threshold needs a better scaling
> for larger machines.

Agree. We may consider that.
But, unlike NUMA counters which do not effect system decision.
We need consider very carefully when increase stat_threshold for all the counters
for larger machines. BTW, this is another topic that we may discuss it in different