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

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Message-ID: <550A2B4C.5030705@huawei.com>
Date:	Thu, 19 Mar 2015 09:50:04 +0800
From:	Zefan Li <lizefan@...wei.com>
To:	Rik van Riel <riel@...hat.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 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.

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