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

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Date:	Wed, 22 Jun 2016 10:07:18 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>, glider@...gle.com,
	hughd@...gle.com, mgorman@...hsingularity.net, mhocko@...nel.org,
	minchan@...nel.org, vbabka@...e.cz, mm-commits@...r.kernel.org
Subject: Re: +
 mm-compaction-split-freepages-without-holding-the-zone-lock-fix.patch added
 to -mm tree

On Tue, Jun 21, 2016 at 05:53:22PM -0700, David Rientjes wrote:
> On Wed, 22 Jun 2016, Joonsoo Kim wrote:
> 
> > On Tue, Jun 21, 2016 at 04:14:28PM -0700, akpm@...ux-foundation.org wrote:
> > > 
> > > The patch titled
> > >      Subject: mm/compaction: split freepages without holding the zone lock fix
> > > has been added to the -mm tree.  Its filename is
> > >      mm-compaction-split-freepages-without-holding-the-zone-lock-fix.patch
> > > 
> > > This patch should soon appear at
> > >     http://ozlabs.org/~akpm/mmots/broken-out/mm-compaction-split-freepages-without-holding-the-zone-lock-fix.patch
> > > and later at
> > >     http://ozlabs.org/~akpm/mmotm/broken-out/mm-compaction-split-freepages-without-holding-the-zone-lock-fix.patch
> > > 
> > > Before you just go and hit "reply", please:
> > >    a) Consider who else should be cc'ed
> > >    b) Prefer to cc a suitable mailing list as well
> > >    c) Ideally: find the original patch on the mailing list and do a
> > >       reply-to-all to that, adding suitable additional cc's
> > > 
> > > *** Remember to use Documentation/SubmitChecklist when testing your code ***
> > > 
> > > The -mm tree is included into linux-next and is updated
> > > there every 3-4 working days
> > > 
> > > ------------------------------------------------------
> > > From: David Rientjes <rientjes@...gle.com>
> > > Subject: mm/compaction: split freepages without holding the zone lock fix
> > > 
> > > If __isolate_free_page() fails, avoid adding to freelist so we don't call
> > > map_pages() with it.
> > > 
> > > Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1606211447001.43430@chino.kir.corp.google.com
> > 
> > I've sent the fix already. I don't care which patch is merged but I guess
> > below series would be merged more cleanly? It's up to Andrew.
> > 
> > Link: http://lkml.kernel.org/r/1466150259-27727-1-git-send-email-iamjoonsoo.kim@lge.com
> > 
> 
> 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.

Thanks.