Re: + mm-compaction-split-freepages-without-holding-the-zone-lock-fix.patch added to -mm tree

From: David Rientjes
Date: Tue Jun 21 2016 - 21:10:27 EST


On Wed, 22 Jun 2016, Joonsoo Kim wrote:

> > Well, http://marc.info/?l=linux-mm&m=146654572331344 fixes an issue that
> > persists at least as far back as 3.11 whereas we can scan entire 256GB+
> > zones needlessly each time compaction_alloc() is called, and that function
> > can be called multiple times for a single page isolated for migration in
> > the case of -EAGAIN. It's been measured that compaction_alloc() can take
> > 15-20% of cpu cycles while faulting thp on very large machines back in the
> > 3.11 kernel. I would suggest that this is an important fix that needs to
> > be included and perhaps backported to stable.
>
> Agreed.
>
> >
> > I don't know the relative importance the reducing the size of page_owner
> > patchset. It appears that the link you provided is a refreshed series of
> > a patchset that is already in -mm? If so, I think the old set should be
> > reverted, and whatever dependencies it has, and then a third version of
> > http://marc.info/?l=linux-mm&m=146654572331344 merged. I can propose that
> > for inclusion in this release cycle if folks agree that it's warranted.
> >
> > The alternative seems to be to rebase your refreshed series on top of -mm
> > with the fix.
>
> I think that page_owner patch is less important. Andrew, could you
> revert whole series? I will refresh series on top of -mm with the
> David's fix.
>

Ok, I'm not exactly sure what the result will look like, so I'll propose a
version of http://marc.info/?l=linux-mm&m=146654572331344 against Linus's
tree and suggest it be backported to stable. I think it should go into
this release cycle as well, but I'll wait for you or Vlastimil to ack it
and see if you agree.