linux-kernel - Re: [PATCH 3/4] cpusets,isolcpus: add file to show isolated cpus in cpuset

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Message-ID: <550A2C48.6080807@redhat.com>
Date:	Wed, 18 Mar 2015 21:54:16 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Zefan Li <lizefan@...wei.com>
CC:	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
	Clark Williams <williams@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Luiz Capitulino <lcapitulino@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	Mike Galbraith <umgwanakikbuti@...il.com>
Subject: Re: [PATCH 3/4] cpusets,isolcpus: add file to show isolated cpus
 in cpuset

On 03/18/2015 09:50 PM, Zefan Li wrote:
> On 2015/3/19 7:40, Rik van Riel wrote:
>> On 03/18/2015 12:47 PM, Tejun Heo wrote:
>>> On Mon, Mar 09, 2015 at 12:12:09PM -0400, riel@...hat.com wrote:
>>>> From: Rik van Riel <riel@...hat.com>
>>>>
>>>> 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.
>>>
>>> Didn't Li say that this is trivially computable from userland?  I'm
>>> not sure this knob actually belongs to cpuset.
>>
>> I don't know whether the information to compute this is
>> always visible from userland.  I am happy to drop this
>> patch if Li prefers things that way, though.
>>
> 
> What I proposed is adding /sys/devices/system/cpu/isolated. Sysfs is
> visible in containers, unless specially configured not so.

OK, are you willing to take patches 1, 2, and the first hunk of patch
4 now? I can submit a patch to add /sys/devices/system/cpu/isolated
on Friday, to the appropriate maintainer.

(taking tomorrow off to go hiking on the last full day of winter)

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