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

From: Michal Hocko
Date: Wed Dec 20 2017 - 05:12:38 EST

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.
Michal Hocko