linux-kernel - Re: Should we be using unlikely() around tests of GFP

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Message-ID: <AANLkTi=9ZNk6w8PxvveWHy5+okfTyKUj3L2ywFOuFjoq@mail.gmail.com>
Date:	Mon, 3 Jan 2011 12:46:45 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	"Theodore Ts'o" <tytso@....edu>
Cc:	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Matt Mackall <mpm@...enic.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>
Subject: Re: Should we be using unlikely() around tests of GFP_ZERO?

On Mon, Jan 3, 2011 at 8:48 AM, Theodore Ts'o <tytso@....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:
>
> -       if (unlikely((flags & __GFP_ZERO) && objp))
> +       if ((flags & __GFP_ZERO) && objp)
>                memset(objp, 0, obj_size(cachep));
>
> Agreed?  If 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.


>
>                                                - Ted
>
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-- 
Kind regards,
Minchan Kim
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