linux-kernel - Re: [PATCH v4 10/10] thp: implement refcounting for huge zero page

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Message-ID: <20121024203329.GA24716@otc-wbsnb-06>
Date:	Wed, 24 Oct 2012 23:33:29 +0300
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Kirill A. Shutemov" <kirill@...temov.name>,
	Andrea Arcangeli <aarcange@...hat.com>, linux-mm@...ck.org,
	Andi Kleen <ak@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 10/10] thp: implement refcounting for huge zero page

On Wed, Oct 24, 2012 at 01:25:52PM -0700, Andrew Morton wrote:
> On Wed, 24 Oct 2012 22:45:52 +0300
> "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> wrote:
> 
> > On Wed, Oct 24, 2012 at 12:22:53PM -0700, Andrew Morton wrote:
> > > 
> > > I'm thinking that such a workload would be the above dd in parallel
> > > with a small app which touches the huge page and then exits, then gets
> > > executed again.  That "small app" sounds realistic to me.  Obviously
> > > one could exercise the zero page's refcount at higher frequency with a
> > > tight map/touch/unmap loop, but that sounds less realistic.  It's worth
> > > trying that exercise as well though.
> > > 
> > > Or do something else.  But we should try to probe this code's
> > > worst-case behaviour, get an understanding of its effects and then
> > > decide whether any such workload is realisic enough to worry about.
> > 
> > Okay, I'll try few memory pressure scenarios.
> 
> Thanks.
> 
> > Meanwhile, could you take patches 01-09? Patch 09 implements simpler
> > allocation scheme. It would be nice to get all other code tested.
> > Or do you see any other blocker?
> 
> I think I would take them all, to get them tested while we're still
> poking at the code.  It's a matter of getting my lazy ass onto reviewing
> the patches.
> 
> The patches have a disturbing lack of reviewed-by's, acked-by's and
> tested-by's on them.  Have any other of the MM lazy asses actually
> spent some time with them yet?

Andrea Revieved-by previous version of the patchset, but I've dropped the
tag after rebase to v3.7-rc1 due not-so-trivial conflicts. Patches 2, 3,
4, 7, 10 had conflicts. Mostly due new MMU notifiers interface.

I mentioned that in cover letter.

-- 
 Kirill A. Shutemov

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