Re: [PATCH v2 3/9] mm, page_owner: convert page_owner_inited to static key

Michal Hocko
2015-11-25T15:46:14Z

On Wed 25-11-15 16:25:33, Peter Zijlstra wrote:
> On Wed, Nov 25, 2015 at 04:08:11PM +0100, Vlastimil Babka wrote:
> > Now I admit I have no idea if there are architectures that don't support jump
> > labels *and* have an expensive atomic read, and whether we care?
>
> atomic_read() is basically always READ_ONCE(), there's a few archs that
> implement it in asm with a 'weird' load instruction, but its still a
> load. The worst is I think an uncached load for blackfin or somesuch.
>
> There's plenty archs that do not support the jump label bits, but
> typically you don't care much about those. I'm not aware of an arch that
> cannot fundamentally implement jump_label support if they wanted to.

OK, I see. Thanks for the clarification! Then I do not have any
objections.

--
Michal Hocko
SUSE Labs