Re: [RFC PATCH 12/12] housekeeping: Reimplement isolcpus on housekeeping

From	Thomas Gleixner <tglx@linutronix.de>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH 12/12] housekeeping: Reimplement isolcpus on housekeeping
Date	2017-08-31 21:00 +0200
Message-ID	<ukCR3-Ul-3@gated-at.bofh.it> (permalink)
References	(3 earlier) <ujsh3-665-3@gated-at.bofh.it> <ujsqL-6aY-27@gated-at.bofh.it> <uju9c-7fp-13@gated-at.bofh.it> <ujv5g-7QO-9@gated-at.bofh.it> <ujwaZ-8sm-11@gated-at.bofh.it>
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On Mon, 28 Aug 2017, Frederic Weisbecker wrote:
> On Mon, Aug 28, 2017 at 06:24:16PM +0200, Peter Zijlstra wrote:
> > On Mon, Aug 28, 2017 at 05:27:15PM +0200, Frederic Weisbecker wrote:
> > > Although for example I guess (IIUC) that if you create an unbound
> > > timer on a NULL domain, it will be stuck on it for ever as we can't
> > > walk any hierarchy from the current CPU domain.
> > 
> > Not sure what you're on about. Timers have their own hierarchy.
> 
> Check out get_nohz_timer_target() which relies on scheduler hierarchies to
> look up a CPU to enqueue an unpinned timer on.

Which is one of the most idiotic things we have in that code
path. Anna-Maria has posted this series which gets rid of that nonsense, by
queueing the timer on the current cpu into a wheel, which gets pulled in by
others. That makes a lot of sense because most of these timers get canceled
before expiry anyway. But we still need to fix the fallout and the few
corner cases to make that work reliably. We'll do that hopefully sooner
than later.

Thanks,

	tglx

Thread

Re: [RFC PATCH 12/12] housekeeping: Reimplement isolcpus on  housekeeping Peter Zijlstra <peterz@infradead.org> - 2017-08-28 12:20 +0200
  Re: [RFC PATCH 12/12] housekeeping: Reimplement isolcpus on  housekeeping Frederic Weisbecker <fweisbec@gmail.com> - 2017-08-28 15:30 +0200
    Re: [RFC PATCH 12/12] housekeeping: Reimplement isolcpus on  housekeeping Peter Zijlstra <peterz@infradead.org> - 2017-08-28 15:40 +0200
      Re: [RFC PATCH 12/12] housekeeping: Reimplement isolcpus on  housekeeping Frederic Weisbecker <fweisbec@gmail.com> - 2017-08-28 17:30 +0200
        Re: [RFC PATCH 12/12] housekeeping: Reimplement isolcpus on  housekeeping Peter Zijlstra <peterz@infradead.org> - 2017-08-28 18:30 +0200
          Re: [RFC PATCH 12/12] housekeeping: Reimplement isolcpus on  housekeeping Christopher Lameter <cl@linux.com> - 2017-08-28 19:00 +0200
          Re: [RFC PATCH 12/12] housekeeping: Reimplement isolcpus on  housekeeping Frederic Weisbecker <fweisbec@gmail.com> - 2017-08-28 19:40 +0200
            Re: [RFC PATCH 12/12] housekeeping: Reimplement isolcpus on  housekeeping Thomas Gleixner <tglx@linutronix.de> - 2017-08-31 21:00 +0200
              Re: [RFC PATCH 12/12] housekeeping: Reimplement isolcpus on  housekeeping Frederic Weisbecker <fweisbec@gmail.com> - 2017-09-01 01:10 +0200

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