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

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Message-Id: <20121024132552.5f9a5f5b.akpm@linux-foundation.org>
Date:	Wed, 24 Oct 2012 13:25:52 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
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, 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?
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