Re: Help Resource Counters Scale Better (v3)

Balbir Singh
2009-08-10T07:42:51Z

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-08-10 15:22:05]:

> On Mon, 10 Aug 2009 14:45:59 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>
> > > Do you agree?
> >
> > Ok. Config is enough at this stage.
> >
> > The last advice for merge is, it's better to show the numbers or
> > ask someone who have many cpus to measure benefits. Then, Andrew can
> > know how this is benefical.
> > (My box has 8 cpus. But maybe your IBM collaegue has some bigger one)
> >
> > In my experience (in my own old trial),
> > - lock contention itself is low. not high.
> > - but cacheline-miss, pingpong is very very frequent.
> >
> > Then, this patch has some benefit logically but, in general,
> > File-I/O, swapin-swapout, page-allocation/initalize etc..dominates
> > the performance of usual apps. You'll have to be careful to select apps
> > to measure the benfits of this patch by application performance.
> > (And this is why I don't feel so much emergency as you do)
> >
>
> Why I say "I want to see the numbers" again and again is that
> this is performance improvement with _bad side effect_.
> If this is an emergent trouble, and need fast-track, which requires us
> "fix small problems later", plz say so.
>

Yes, this is an emergent trouble, I've gotten reports of the lock
showing up on 16 to 64 ways.

> I have no objection to this approach itself because I can't think of
> something better, now. percpu-counter's error tolerance is a generic
> problem and we'll have to visit this anyway.
>

Yes, my plan is to then later add a strict/no-strict accounting layer
and allow users to choose. Keep root as non-script as we don't
support limit setting on root now.