linux-kernel - Re: [PATCH v2] cpuset: use static key better and convert to new API

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Date:	Thu, 14 Apr 2016 16:28:50 +0800
From:	Zefan Li <lizefan@...wei.com>
To:	Vlastimil Babka <vbabka@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	Mel Gorman <mgorman@...hsingularity.net>,
	Peter Zijlstra <peterz@...radead.org>,
	David Rientjes <rientjes@...gle.com>,
	<cgroups@...r.kernel.org>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] cpuset: use static key better and convert to new API

On 2016/4/6 17:19, Vlastimil Babka wrote:
> An important function for cpusets is cpuset_node_allowed(), which optimizes on
> the fact if there's a single root CPU set, it must be trivially allowed. But
> the check "nr_cpusets() <= 1" doesn't use the cpusets_enabled_key static key
> the right way where static keys eliminate branching overhead with jump labels.
> 
> This patch converts it so that static key is used properly. It's also switched
> to the new static key API and the checking functions are converted to return
> bool instead of int. We also provide a new variant __cpuset_zone_allowed()
> which expects that the static key check was already done and they key was
> enabled. This is needed for get_page_from_freelist() where we want to also
> avoid the relatively slower check when ALLOC_CPUSET is not set in alloc_flags.
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>

Looks good to me.

Acked-by: Zefan Li <lizefan@...wei.com>