linux-kernel - Re: [PATCH 1/2] thp: fix anononymous page accounting in fallback path for COW of HZP

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Message-ID: <20121203081504.GA12070@otc-wbsnb-06>
Date:	Mon, 3 Dec 2012 10:15:04 +0200
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Bob Liu <lliubbo@...il.com>
Cc:	Jiri Slaby <jslaby@...e.cz>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>,
	David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH 1/2] thp: fix anononymous page accounting in fallback
 path for COW of HZP

On Mon, Dec 03, 2012 at 11:14:38AM +0800, Bob Liu wrote:
> On Fri, Nov 30, 2012 at 11:03 PM, Kirill A. Shutemov
> <kirill.shutemov@...ux.intel.com> wrote:
> > From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> >
> > Don't forget to account newly allocated page in fallback path for
> > copy-on-write of huge zero page.
> >
> 
> What about fallback path in do_huge_pmd_wp_page_fallback()?
> I think we should also account newly allocated page in it.

No. Normal huge pages has already accounted on fork(). See
copy_huge_pmd().

Huge zero page (as 4k zero page) doesn't contribute to RSS, so we need to
account the page which replaces huge zero page on COW.
-- 
 Kirill A. Shutemov

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