linux-kernel - Re: [PATCH 8/9] sched/psi: add kernel cmdline parameter psi_inner

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Message-ID: <94ddcd31-e168-06ed-c0f9-2ea25b802d60@bytedance.com>
Date:   Thu, 4 Aug 2022 10:02:12 +0800
From:   Chengming Zhou <zhouchengming@...edance.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Johannes Weiner <hannes@...xchg.org>, surenb@...gle.com,
        mingo@...hat.com, peterz@...radead.org, corbet@....net,
        akpm@...ux-foundation.org, rdunlap@...radead.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        songmuchun@...edance.com, cgroups@...r.kernel.org
Subject: Re: [PATCH 8/9] sched/psi: add kernel cmdline parameter
 psi_inner_cgroup

On 2022/8/4 01:58, Tejun Heo wrote:
> Hello,
> 
> On Wed, Aug 03, 2022 at 08:17:22PM +0800, Chengming Zhou wrote:
>>> Assuming the above isn't wrong, if we can figure out how we can re-enable
>>> it, which is more difficult as the counters need to be resynchronized with
>>> the current state, that'd be ideal. Then, we can just allow each cgroup to
>>> enable / disable PSI reporting dynamically as they see fit.
>>
>> This method is more fine-grained but more difficult like you said above.
>> I think it may meet most needs to disable PSI stats in intermediate cgroups?
> 
> So, I'm not necessarily against implementing something easier but we at
> least wanna get the interface right, so that if we decide to do the full
> thing later we can easily expand on the existing interface. ie. let's please
> not be too hacky. I don't think it'd be that difficult to implement
> per-cgroup disable-only operation that we can later expand to allow
> re-enabling, right?

Agree, the interface is important, per-cgroup disable-only operation maybe easier
to implement. I will look into this more.

Thanks!