linux-kernel - Re: [PATCH 16/28] mm, page_alloc: Move __GFP_HARDWALL modifications out of the fastpath

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Message-ID: <571F77A0.2010207@suse.cz>
Date:	Tue, 26 Apr 2016 16:13:52 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Mel Gorman <mgorman@...hsingularity.net>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Jesper Dangaard Brouer <brouer@...hat.com>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 16/28] mm, page_alloc: Move __GFP_HARDWALL modifications
 out of the fastpath

On 04/15/2016 11:07 AM, Mel Gorman wrote:
> __GFP_HARDWALL only has meaning in the context of cpusets but the fast path
> always applies the flag on the first attempt. Move the manipulations into
> the cpuset paths where they will be masked by a static branch in the common
> case.
>
> With the other micro-optimisations in this series combined, the impact on
> a page allocator microbenchmark is
>
>                                             4.6.0-rc2                  4.6.0-rc2
>                                         decstat-v1r20                micro-v1r20
> Min      alloc-odr0-1               381.00 (  0.00%)           377.00 (  1.05%)
> Min      alloc-odr0-2               275.00 (  0.00%)           273.00 (  0.73%)
> Min      alloc-odr0-4               229.00 (  0.00%)           226.00 (  1.31%)
> Min      alloc-odr0-8               199.00 (  0.00%)           196.00 (  1.51%)
> Min      alloc-odr0-16              186.00 (  0.00%)           183.00 (  1.61%)
> Min      alloc-odr0-32              179.00 (  0.00%)           175.00 (  2.23%)
> Min      alloc-odr0-64              174.00 (  0.00%)           172.00 (  1.15%)
> Min      alloc-odr0-128             172.00 (  0.00%)           170.00 (  1.16%)
> Min      alloc-odr0-256             181.00 (  0.00%)           183.00 ( -1.10%)
> Min      alloc-odr0-512             193.00 (  0.00%)           191.00 (  1.04%)
> Min      alloc-odr0-1024            201.00 (  0.00%)           199.00 (  1.00%)
> Min      alloc-odr0-2048            206.00 (  0.00%)           204.00 (  0.97%)
> Min      alloc-odr0-4096            212.00 (  0.00%)           210.00 (  0.94%)
> Min      alloc-odr0-8192            215.00 (  0.00%)           213.00 (  0.93%)
> Min      alloc-odr0-16384           216.00 (  0.00%)           214.00 (  0.93%)
>
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>

Acked-by: Vlastimil Babka <vbabka@...e.cz>