Re: Should we be using unlikely() around tests of GFP_ZERO?

From: Matt Mackall
Date: Mon Jan 03 2011 - 12:23:53 EST


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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