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Date: Mon, 3 Jan 2011 12:46:45 +0900
Message-ID: <AANLkTi=9ZNk6w8PxvveWHy5+okfTyKUj3L2ywFOuFjoq@mail.gmail.com>
Subject: Re: Should we be using unlikely() around tests of GFP_ZERO?
From: Minchan Kim <minchan.kim@gmail.com>
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Sender: owner-linux-mm@kvack.org
To: Theodore Ts'o <tytso@mit.edu>
Cc: Christoph Lameter <cl@linux-foundation.org>, Pekka Enberg <penberg@cs.helsinki.fi>, Matt Mackall <mpm@selenic.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>
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On Mon, Jan 3, 2011 at 8:48 AM, Theodore Ts'o <tytso@mit.edu> wrote:
>
> Given the patches being busily submitted by trivial patch submitters to
> make use kmem_cache_zalloc(), et. al, I believe we should remove the
> unlikely() tests around the (gfp_flags & __GFP_ZERO) tests, such as:
>
> - =A0 =A0 =A0 if (unlikely((flags & __GFP_ZERO) && objp))
> + =A0 =A0 =A0 if ((flags & __GFP_ZERO) && objp)
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0memset(objp, 0, obj_size(cachep));
>
> Agreed? =A0If so, I'll send a patch...

I support it.

Recently Steven tried to gather the information.
http://thread.gmane.org/gmane.linux.kernel/1072767
Maybe he might have a number for that.


>
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0 =A0- Ted
>
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--=20
Kind regards,
Minchan Kim

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