Re: [PATCH 1/4] mm, page_alloc: add likely macro to help compiler optimization

Johannes Weiner
2013-08-02T20:47:22Z

On Fri, Aug 02, 2013 at 06:27:22PM +0200, Michal Hocko wrote:
> On Fri 02-08-13 11:07:56, Joonsoo Kim wrote:
> > We rarely allocate a page with ALLOC_NO_WATERMARKS and it is used
> > in slow path. For making fast path more faster, add likely macro to
> > help compiler optimization.
>
> The code is different in mmotm tree (see mm: page_alloc: rearrange
> watermark checking in get_page_from_freelist)

Yes, please rebase this on top.

> Besides that, make sure you provide numbers which prove your claims
> about performance optimizations.

Isn't that a bit overkill? We know it's a likely path (we would
deadlock constantly if a sizable portion of allocations were to ignore
the watermarks). Does he have to justify that likely in general makes
sense?