linux-kernel - Re: [RFC V2 05/12] cpuset: Add cpuset_inc() inside cpuset

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Date:   Mon, 30 Jan 2017 20:30:03 +0000
From:   Mel Gorman <mgorman@...e.de>
To:     Anshuman Khandual <khandual@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org, mhocko@...e.com,
        vbabka@...e.cz, minchan@...nel.org,
        aneesh.kumar@...ux.vnet.ibm.com, bsingharora@...il.com,
        srikar@...ux.vnet.ibm.com, haren@...ux.vnet.ibm.com,
        jglisse@...hat.com, dave.hansen@...el.com, dan.j.williams@...el.com
Subject: Re: [RFC V2 05/12] cpuset: Add cpuset_inc() inside cpuset_init()

On Mon, Jan 30, 2017 at 09:05:46AM +0530, Anshuman Khandual wrote:
> Currently cpusets_enabled() wrongfully returns 0 even if we have a root
> cpuset configured on the system. This got missed when jump level was
> introduced in place of number_of_cpusets with the commit 664eeddeef65
> ("mm: page_alloc: use jump labels to avoid checking number_of_cpusets")
> . This fixes the problem so that cpusets_enabled() returns positive even
> for the root cpuset.
> 
> Fixes: 664eeddeef65 ("mm: page_alloc: use jump labels to avoid")
> Signed-off-by: Anshuman Khandual <khandual@...ux.vnet.ibm.com>

Superficially, this appears to always activate the cpuset_enabled
branch() when it doesn't really make sense that the root cpuset be
restricted. I strongly suspect it should be altered to cpuset_inc only
if the root cpuset is configured to isolate memory.

-- 
Mel Gorman
SUSE Labs