Date:   Tue, 7 Feb 2023 13:59:00 +0100
From:   Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
To:     Frederic Weisbecker <frederic@kernel.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Waiman Long <longman@redhat.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Michal Hocko <mhocko@suse.com>,
        Marcelo Tosatti <mtosatti@redhat.com>,
        Leonardo <leobras@redhat.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Shakeel Butt <shakeelb@google.com>,
        Muchun Song <muchun.song@linux.dev>,
        Andrew Morton <akpm@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>, cgroups@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [PATCH 1/2] sched/isolation: Merge individual nohz_full features
 into a common housekeeping flag
Message-ID: <20230207125900.GA24523@blackbody.suse.cz>
References: <20230203232409.163847-1-frederic@kernel.org>
 <20230203232409.163847-2-frederic@kernel.org>
 <20230206155107.GA31453@blackbody.suse.cz>
 <Y+I61dp5qPkWK4s2@lothringen>
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On Tue, Feb 07, 2023 at 12:49:41PM +0100, Frederic Weisbecker <frederic@kernel.org> wrote:
> But what do we need these annotations for? The only outcome I've ever
> seen with these is that it confuses everyone.

Take that as a note of a lone actor then who found it useful documenting
relations between various parts of the code.

> This way I can add the support for each part smoothly.

Yeah, that makes sense.

> For example first patch moves HK_TYPE_TIMER to HK_TYPE_KERNEL_NOISE
> and unbound timers are supported by cpuset.kernel_noise, second patch
> moves HK_TYPE_WQ to HK_TYPE_KERNEL_NOISE and unbound workqueues are
> supported by cpuset.kernel_noise, etc until all of them turned by
> nohz_full= are supported...

So does this mean you'll re-introduce the finer grained HK_* flags
again?

The idea (not only mine?) is that this would extend
cpuset.cpus.partition that only allows HK_TYPE_DOMAIN analogy. The
mapping to individual flags may not be exposed to users. The graduality
could be achieved by adding more flags under user_exposed_term.

Just to be on the same page -- that's how I understand it, the original
HK_* resolution turned out impractical for users and that's why the
direction is towards some loose combinations representing user
intentions. Is that right?


Cheers,
Michal

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