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

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Date:	Tue, 05 Oct 2010 13:38:21 -0400
From:	Rik van Riel <riel@...hat.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>,
	Nick Piggin <npiggin@...nel.dk>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 2/3] Retry page fault when blocking on disk transfer.

On 10/05/2010 03:53 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>

Acked-by: Rik van Riel <riel@...hat.com>

Looks like it should be relatively easy to do something
similar in do_swap_page also.
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