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

[Ted Ts'o]

On Mon, Jan 03, 2011 at 09:40:57AM +0200, Pekka Enberg wrote:
> I guess the rationale here is that if you're going to take the hit of
> memset() you can take the hit of unlikely() as well. We're optimizing
> for hot call-sites that allocate a small amount of memory and
> initialize everything themselves. That said, I don't think the
> unlikely() annotation matters much either way and am for removing it
> unless people object to that.

I suspect for many slab caches, all of the slab allocations for a
given slab cache type will have the GFP_ZERO flag passed.  So maybe it
would be more efficient to zap the entire page when it is pressed into
service for a particular slab cache, so we can avoid needing to use
memset on a per-object basis?

						- Ted
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