Re: [mm] 755d6edc1a: will-it-scale.per_process_ops -4.1% regression

[Michal Hocko]

On Tue 06-08-19 20:00:24, Minchan Kim wrote:
> On Tue, Aug 06, 2019 at 10:04:15AM +0200, Michal Hocko wrote:
> > On Tue 06-08-19 15:05:47, kernel test robot wrote:
> > > Greeting,
> > > 
> > > FYI, we noticed a -4.1% regression of will-it-scale.per_process_ops due to commit:
> > 
> > I have to confess I cannot make much sense from numbers because they
> > seem to be too volatile and the main contributor doesn't stand up for
> > me. Anyway, regressions on microbenchmarks like this are not all that
> > surprising when a locking is slightly changed and the critical section
> > made shorter. I have seen that in the past already.
> 
> I guess if it's multi process workload. The patch will give more chance
> to be scheduled out so TLB miss ratio would be bigger than old.
> I see it's natural trade-off for latency vs. performance so only thing
> I could think is just increase threshold from 32 to 64 or 128?

This still feels like a magic number tunning, doesn't it?

-- 
Michal Hocko
SUSE Labs