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

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Message-Id: <d7b471ea-4d37-58bd-dacc-d61599d6b71f@linux.vnet.ibm.com>
Date:   Tue, 31 Jan 2017 21:00:33 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     Vlastimil Babka <vbabka@...e.cz>, Mel Gorman <mgorman@...e.de>,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org, mhocko@...e.com,
        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 01/31/2017 08:06 PM, Vlastimil Babka wrote:
> On 01/30/2017 09:30 PM, Mel Gorman wrote:
>> 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.
> 
> Yes that's why root cpuset doesn't "count", as it's not supposed to be
> restricted (it's also documented in cpusets.txt) Thus the "Fixes:" tag
> is very misleading.

Agreed, I have removed the "Fixes: " tag in the proposed RFC already
posted on this thread where it puts it as a new enablement instead
and an addition to the capability what we already have with cpuset.
It will be great if you can please take a look and provide feedback.