Re: [PATCH 4/4] mm: numa: Slow PTE scan rate if migration failures occur

Dave Chinner
2015-03-17T07:07:40Z

On Thu, Mar 12, 2015 at 06:49:26PM +0000, Mel Gorman wrote:
> On Thu, Mar 12, 2015 at 09:20:36AM -0700, Linus Torvalds wrote:
> > On Thu, Mar 12, 2015 at 6:10 AM, Mel Gorman <mgorman@suse.de> wrote:
> > >
> > > I believe you're correct and it matches what was observed. I'm still
> > > travelling and wireless is dirt but managed to queue a test using pmd_dirty
> >
> > Ok, thanks.
> >
> > I'm not entirely happy with that change, and I suspect the whole
> > heuristic should be looked at much more (maybe it should also look at
> > whether it's executable, for example), but it's a step in the right
> > direction.
> >
>
> I can follow up when I'm back in work properly. As you have already pulled
> this in directly, can you also consider pulling in "mm: thp: return the
> correct value for change_huge_pmd" please? The other two patches were very
> minor can be resent through the normal paths later.

TO close the loop here, now I'm back home and can run tests:

config 3.19 4.0-rc1 4.0-rc4
defaults 8m08s 9m34s 9m14s
-o ag_stride=-1 4m04s 4m38s 4m11s
-o bhash=101073 6m04s 17m43s 7m35s
-o ag_stride=-1,bhash=101073 4m54s 9m58s 7m50s

It's better but there are still significant regressions, especially
for the large memory footprint cases. I haven't had a chance to look
at any stats or profiles yet, so I don't know yet whether this is
still page fault related or some other problem....

Cheers,

Dave
--
Dave Chinner
david@fromorbit.com