linux-kernel - Re: [LKP] [lkp] [xfs] 68a9f5e700: aim7.jobs-per-min -13.6% regression

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Message-ID: <20160819090017.GF32619@dhcp22.suse.cz>
Date:   Fri, 19 Aug 2016 11:00:17 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Dave Chinner <david@...morbit.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Minchan Kim <minchan@...nel.org>,
        Vladimir Davydov <vdavydov@...tuozzo.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Bob Peterson <rpeterso@...hat.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        Christoph Hellwig <hch@....de>,
        Wu Fengguang <fengguang.wu@...el.com>, LKP <lkp@...org>,
        Tejun Heo <tj@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [LKP] [lkp] [xfs] 68a9f5e700: aim7.jobs-per-min -13.6% regression

On Thu 18-08-16 15:25:40, Linus Torvalds wrote:
[...]
> So just for testing purposes, you could try changing that
> 
>         return alloc_pages(gfp, 0);
> 
> in __page_cache_alloc() into something like
> 
>         return alloc_pages_node(cpu_to_node(raw_smp_processor_id())), gfp, 0);

That would break mempolicies AFAICS. Anyway, I might be missing
something (the mempolicy kod has a strange sense for aesthetic) but the
normal case without any explicit mempolicy should use default_policy
which is MPOL_PREFERRED and MPOL_F_LOCAL which means numa_node_id() so
the local node. So the above two should do the same thing unless I have
missing something.
-- 
Michal Hocko
SUSE Labs