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Message-ID: <20151125154607.GO27283@dhcp22.suse.cz>
Date:	Wed, 25 Nov 2015 16:46:07 +0100
From:	Michal Hocko <mhocko@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Minchan Kim <minchan@...nel.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Mel Gorman <mgorman@...e.de>
Subject: Re: [PATCH v2 3/9] mm, page_owner: convert page_owner_inited to
 static key

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
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