linux-kernel - Re: [PATCH v4] cpuset: Enable cpuset controller in default hierarchy

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Date:   Fri, 9 Mar 2018 18:06:29 -0500
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Mike Galbraith <efault@....de>, Tejun Heo <tj@...nel.org>,
        Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Ingo Molnar <mingo@...hat.com>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        kernel-team@...com, pjt@...gle.com, luto@...capital.net,
        torvalds@...ux-foundation.org, Roman Gushchin <guro@...com>
Subject: Re: [PATCH v4] cpuset: Enable cpuset controller in default hierarchy

On 03/09/2018 05:17 PM, Peter Zijlstra wrote:
> On Fri, Mar 09, 2018 at 03:43:34PM -0500, Waiman Long wrote:
>> The isolcpus= parameter just reduce the cpus available to the rests of
>> the system. The cpuset controller does look at that value and make
>> adjustment accordingly, but it has no dependence on exclusive cpu/mem
>> features of cpuset.
> The isolcpus= boot param is donkey shit and needs to die. cpuset _used_
> to be able to fully replace it, but with the advent of cgroup 'feature'
> this got lost.
>
> And instead of fixing it, you're making it _far_ worse. You completely
> removed all the bits that allow repartitioning the scheduler domains.
>
> Mike is completely right, full NAK on any such approach.

So you are talking about sched_relax_domain_level and
sched_load_balance. I have not removed any bits. I just haven't exposed
them yet. It does seem like these 2 control knobs are useful from the
scheduling perspective. Do we also need cpu_exclusive or just the two
sched control knobs are enough?

Cheers,
Longman