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

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Date:	Tue, 21 Jun 2016 18:09:37 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....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 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.