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From: David Chinner <dgc@sgi.com>
To: Andrew Morton <akpm@osdl.org>
Cc: "Martin J. Bligh" <mbligh@mbligh.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Ingo Molnar <mingo@elte.hu>, David Chinner <dgc@sgi.com>
Subject: Re: [PATCH] mm: remove global locks from mm/highmem.c
Date: Wed, 31 Jan 2007 11:44:36 +1100	[thread overview]
Message-ID: <20070131004436.GS44411608@melbourne.sgi.com> (raw)
In-Reply-To: <20070129181557.d4d17dd0.akpm@osdl.org>

On Mon, Jan 29, 2007 at 06:15:57PM -0800, Andrew Morton wrote:
> We still don't know what is the source of kmap() activity which
> necessitated this patch btw.  AFAIK the busiest source is ext2 directories,
> but perhaps NFS under certain conditions?
> 
> <looks at xfs_iozero>
> 
> ->prepare_write no longer requires that the caller kmap the page.

Agreed, but don't we (xfs_iozero) have to map it first to zero it?

I think what you are saying here, Andrew, is that we can
do something like:

	page = grab_cache_page
	->prepare_write(page)
	kaddr = kmap_atomic(page, KM_USER0)
	memset(kaddr+offset, 0, bytes)
	flush_dcache_page(page)
	kunmap_atomic(kaddr, KM_USER0)
	->commit_write(page)

to avoid using kmap() altogether?

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group

  reply	other threads:[~2007-01-31  0:45 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-28 14:11 Peter Zijlstra
2007-01-28 14:49 ` Christoph Hellwig
2007-01-28 15:17   ` Ingo Molnar
2007-01-28 15:28     ` Christoph Hellwig
2007-01-28 15:48       ` Ingo Molnar
2007-01-28 15:54         ` Christoph Hellwig
2007-01-28 18:19           ` Ingo Molnar
2007-01-28 22:29 ` Andrew Morton
2007-01-29  2:52   ` Nick Piggin
2007-01-29  9:44   ` Peter Zijlstra
2007-01-30  1:31     ` Martin J. Bligh
2007-01-30  1:41       ` Andrew Morton
2007-01-30  1:49         ` Martin J. Bligh
2007-01-30  2:15           ` Andrew Morton
2007-01-31  0:44             ` David Chinner [this message]
2007-01-31  1:11               ` Andrew Morton
2007-01-31  3:22                 ` David Chinner
2007-02-02 12:05                   ` Christoph Hellwig
2007-02-02 19:24                     ` Matt Mackall
2007-02-02 23:16                       ` David Chinner
2007-02-02 23:14                     ` David Chinner
2007-01-29 19:08   ` Ingo Molnar
2007-01-29 19:19     ` Hugh Dickins
2007-01-29 19:53       ` Ingo Molnar
2007-01-29 20:06     ` Ingo Molnar
2007-01-30  2:02     ` Nick Piggin

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