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

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Message-ID: <1294075426.3109.99.camel@calx>
Date:	Mon, 03 Jan 2011 11:23:46 -0600
From:	Matt Mackall <mpm@...enic.com>
To:	Theodore Ts'o <tytso@....edu>
Cc:	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...helsinki.fi>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: Should we be using unlikely() around tests of GFP_ZERO?

On Sun, 2011-01-02 at 18:48 -0500, Theodore Ts'o 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...

Sounds good to me.

We might consider dropping this flag and making the decision statically
(ie alloc vs zalloc), at least for slab objects.

-- 
Mathematics is the supreme nostalgia of our time.


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