linux-kernel - Re: [PATCH 2/3] Retry page fault when blocking on disk transfer.

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Message-ID: <4CABF4C0.8060405@zytor.com>
Date:	Tue, 05 Oct 2010 21:02:08 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Michel Lespinasse <walken@...gle.com>
CC:	linux-mm@...ck.org, Linus Torvalds <torvalds@...ux-foundation.org>,
	Ying Han <yinghan@...gle.com>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Nick Piggin <npiggin@...nel.dk>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/3] Retry page fault when blocking on disk transfer.

On 10/05/2010 12:53 AM, Michel Lespinasse wrote:
> This change reduces mmap_sem hold times that are caused by waiting for
> disk transfers when accessing file mapped VMAs. It introduces the
> VM_FAULT_ALLOW_RETRY flag, which indicates that the call site wants
> mmap_sem to be released if blocking on a pending disk transfer.
> In that case, filemap_fault() returns the VM_FAULT_RETRY status bit
> and do_page_fault() will then re-acquire mmap_sem and retry the page fault.
> It is expected that the retry will hit the same page which will now be
> cached, and thus it will complete with a low mmap_sem hold time.
> 
> Signed-off-by: Michel Lespinasse <walken@...gle.com>
> ---
>  arch/x86/mm/fault.c |   38 ++++++++++++++++++++++++++------------
>  include/linux/mm.h  |    2 ++
>  mm/filemap.c        |   23 ++++++++++++++++++++++-
>  mm/memory.c         |    3 ++-
>  4 files changed, 52 insertions(+), 14 deletions(-)
> 

Acked-by: H. Peter Anvin <hpa@...or.com>

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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