Re: page fault scalability patch V12: rss tasklist vs sloppy rss

Andrew Morton
2004-12-09T22:52:37Z

Christoph Lameter <clameter@sgi.com> wrote:
>
> On Thu, 9 Dec 2004, Hugh Dickins wrote:
>
> > How do the scalability figures compare if you omit patch 7/7 i.e. revert
> > the per-task rss complications you added in for Linus? I remain a fan
> > of sloppy rss, which you earlier showed to be accurate enough (I'd say),
> > though I guess should be checked on other architectures than your ia64.
> > I can't see the point of all that added ugliness for numbers which don't
> > need to be precise - but perhaps there's no way of rearranging fields,
> > and the point at which mm->(anon_)rss is updated (near up of mmap_sem?),
> > to avoid destructive cacheline bounce. What I'm asking is, do you have
> > numbers to support 7/7? Perhaps it's the fact you showed up to 512 cpus
> > this time, but only up to 32 with sloppy rss? The ratios do look better
> > with the latest, but the numbers are altogether lower so we don't know.
>
> Here is a full set of numbers for sloppy and tasklist.

Yes, but that only tests the thing-which-you're-trying-to-improve. We also
need to work out the impact of that tasklist walk on other people's worst
cases.

> sloppy (2.6.10-bk14-rss-sloppy-prefault):

It would be helpful if you could generate a breif summary of benchmarking
results as well as dumping the raw numbers, please.