linux-kernel - Re: [PATCH v2 3/9] mm, page_owner: convert page_owner

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Message-ID: <20151125145202.GL27283@dhcp22.suse.cz>
Date:	Wed, 25 Nov 2015 15:52:02 +0100
From:	Michal Hocko <mhocko@...nel.org>
To:	Vlastimil Babka <vbabka@...e.cz>
Cc:	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 Tue 24-11-15 13:36:15, Vlastimil Babka wrote:
> CONFIG_PAGE_OWNER attempts to impose negligible runtime overhead when enabled
> during compilation, but not actually enabled during runtime by boot param
> page_owner=on. This overhead can be further reduced using the static key
> mechanism, which this patch does.

Is this really worth doing? If we do not have jump labels then the check
will be atomic rather than a simple access, so it would be more costly,
no? Or am I missing something?
-- 
Michal Hocko
SUSE Labs
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