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SubjectRe: [PATCH 19/28] mm, page_alloc: Reduce cost of fair zone allocation policy retry
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On 04/15/2016 11:07 AM, Mel Gorman wrote:
> The fair zone allocation policy is not without cost but it can be reduced
> slightly. This patch removes an unnecessary local variable, checks the
> likely conditions of the fair zone policy first, uses a bool instead of
> a flags check and falls through when a remote node is encountered instead
> of doing a full restart. The benefit is marginal but it's there
>
> 4.6.0-rc2 4.6.0-rc2
> decstat-v1r20 optfair-v1r20
> Min alloc-odr0-1 377.00 ( 0.00%) 380.00 ( -0.80%)
> Min alloc-odr0-2 273.00 ( 0.00%) 273.00 ( 0.00%)
> Min alloc-odr0-4 226.00 ( 0.00%) 227.00 ( -0.44%)
> Min alloc-odr0-8 196.00 ( 0.00%) 196.00 ( 0.00%)
> Min alloc-odr0-16 183.00 ( 0.00%) 183.00 ( 0.00%)
> Min alloc-odr0-32 175.00 ( 0.00%) 173.00 ( 1.14%)
> Min alloc-odr0-64 172.00 ( 0.00%) 169.00 ( 1.74%)
> Min alloc-odr0-128 170.00 ( 0.00%) 169.00 ( 0.59%)
> Min alloc-odr0-256 183.00 ( 0.00%) 180.00 ( 1.64%)
> Min alloc-odr0-512 191.00 ( 0.00%) 190.00 ( 0.52%)
> Min alloc-odr0-1024 199.00 ( 0.00%) 198.00 ( 0.50%)
> Min alloc-odr0-2048 204.00 ( 0.00%) 204.00 ( 0.00%)
> Min alloc-odr0-4096 210.00 ( 0.00%) 209.00 ( 0.48%)
> Min alloc-odr0-8192 213.00 ( 0.00%) 213.00 ( 0.00%)
> Min alloc-odr0-16384 214.00 ( 0.00%) 214.00 ( 0.00%)
>
> The benefit is marginal at best but one of the most important benefits,
> avoiding a second search when falling back to another node is not triggered
> by this particular test so the benefit for some corner cases is understated.
>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>

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


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