linux-kernel - Re: [PATCH 1/2] sched/isolation: Merge individual nohz_full features into a common housekeeping flag

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Date:   Mon, 6 Feb 2023 16:51:09 +0100
From:   Michal Koutný <mkoutny@...e.com>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Michal Hocko <mhocko@...e.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Leonardo <leobras@...hat.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <muchun.song@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>, cgroups@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH 1/2] sched/isolation: Merge individual nohz_full features
 into a common housekeeping flag

Hello Frederic.

On Sat, Feb 04, 2023 at 12:24:08AM +0100, Frederic Weisbecker <frederic@...nel.org> wrote:
> The individual isolation features turned on by nohz_full were initially
> split in order for each of them to be tunable through cpusets. However
> plans have changed in favour of an interface (be it cpusets or sysctl)
> grouping all these features to be turned on/off altogether.
> Then should the need ever arise, the interface can still be expanded
> to handle the individual isolation features.
> 
> Therefore the current isolation split between tick/timer/workqueue/rcu/
> kthreads/misc doesn't make sense anymore.

Why it doesn't make sense? I think it's a useful annotation of
respective operations wrt CPU isolation.

The grouping you did into HK_TYPE_KERNEL_NOISE (or even coarser) should
IMO be done at the place where it'll be exposed into the favored
interface (like it's with nohz_full=).

Thanks,
Michal

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