Re: Help Resource Counters Scale Better (v3)

KAMEZAWA Hiroyuki
2009-08-10T06:23:53Z

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.

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.

Thanks,
-Kame