linux-kernel - Re: [PATCH v3 10/10] thp: implement refcounting for huge zero page

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Message-ID: <20120913171613.GJ3388@redhat.com>
Date:	Thu, 13 Sep 2012 19:16:13 +0200
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	Andi Kleen <ak@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill@...temov.name>
Subject: Re: [PATCH v3 10/10] thp: implement refcounting for huge zero page

Hi Kirill,

On Wed, Sep 12, 2012 at 01:07:53PM +0300, Kirill A. Shutemov wrote:
> -	hpage = alloc_pages(GFP_TRANSHUGE | __GFP_ZERO, HPAGE_PMD_ORDER);

The page is likely as large as a pageblock so it's unlikely to create
much fragmentation even if the __GFP_MOVABLE is set. Said that I guess
it would be more correct if __GFP_MOVABLE was clear, like
(GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE because this page isn't
really movable (it's only reclaimable).

The xchg vs xchgcmp locking also looks good.

Reviewed-by: Andrea Arcangeli <aarcange@...hat.com>

Thanks,
Andrea
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