linux-kernel - Re: [PATCH v4 2/2] cpusets,isolcpus: add file to show isolated cpus in cpuset

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Message-ID: <54F47534.7070204@redhat.com>
Date:	Mon, 02 Mar 2015 09:35:32 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Mike Galbraith <umgwanakikbuti@...il.com>,
	Peter Zijlstra <peterz@...radead.org>
CC:	Zefan Li <lizefan@...wei.com>, linux-kernel@...r.kernel.org,
	Clark Williams <williams@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Luiz Capitulino <lcapitulino@...hat.com>,
	David Rientjes <rientjes@...gle.com>, cgroups@...r.kernel.org
Subject: Re: [PATCH v4 2/2] cpusets,isolcpus: add file to show isolated cpus
 in cpuset

On 03/02/2015 07:44 AM, Mike Galbraith wrote:
> On Mon, 2015-03-02 at 10:09 +0100, Peter Zijlstra wrote:
>> On Thu, Feb 26, 2015 at 12:12:31PM -0500, Rik van Riel wrote:
>>> Subject: cpusets,isolcpus: add file to show isolated cpus in cpuset
>>>
>>> The previous patch makes it so the code skips over isolcpus when
>>> building scheduler load balancing domains. This makes it hard to
>>> see for a user which of the CPUs in a cpuset are participating in
>>> load balancing, and which ones are isolated cpus.
>>>
>>> Add a cpuset.isolcpus file with info on which cpus in a cpuset are
>>> isolated CPUs.
>>>
>>> This file is read-only for now. In the future we could extend things
>>> so isolcpus can be changed at run time, for the root (system wide)
>>> cpuset only.
>>>
>>> Acked-by: David Rientjes <rientjes@...gle.com>
>>> Cc: Peter Zijlstra <peterz@...radead.org>
>>> Cc: Clark Williams <williams@...hat.com>
>>> Cc: Li Zefan <lizefan@...wei.com>
>>> Cc: Ingo Molnar <mingo@...hat.com>
>>> Cc: Luiz Capitulino <lcapitulino@...hat.com>
>>> Cc: David Rientjes <rientjes@...gle.com>
>>> Cc: Mike Galbraith <umgwanakikbuti@...il.com>
>>> Cc: cgroups@...r.kernel.org
>>> Signed-off-by: Rik van Riel <riel@...hat.com>
>>
>> So let me start off by saying I hate isolcpus ;-)
>>
>> Let me further state that I had hopes we could extend cpusets to
>> natively provide the functionality isolcpus has, and kill isolcpus.
> 
> +1
> 
> That's where nohz_full goop belongs too.

Except nohz_full and isolcpus are very much global attributes of
each CPU, so I am not sure whether it would make sense to allow
configuration of this attribute anywhere other than the root
cpuset.

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