Re: clocksource_watchdog causing scheduling of timers every second (was [v13] support "task_isolation" mode)

From	Christoph Lameter <cl@linux.com>
Newsgroups	linux.kernel
Subject	Re: clocksource_watchdog causing scheduling of timers every second (was [v13] support "task_isolation" mode)
Date	2016-08-12 01:10 +0200
Message-ID	<s57gS-25e-25@gated-at.bofh.it> (permalink)
References	(5 earlier) <rYR58-6Qr-19@gated-at.bofh.it> <rZxxo-6F-9@gated-at.bofh.it> <s4K0W-2GI-29@gated-at.bofh.it> <s4TQC-1tP-23@gated-at.bofh.it> <s56Ea-1t7-11@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, 11 Aug 2016, Paul E. McKenney wrote:

> > With modern Intel we could run it on one CPU per package I think, but at
> > the same time, too much in NOHZ_FULL assumes the TSC is indeed sane so
> > it doesn't make sense to me to keep the watchdog running, when it
> > triggers it would also have to kill all NOHZ_FULL stuff, which would
> > probably bring the entire machine down..
>
> Well, you -could- force a very low priority CPU-bound task to run on
> all nohz_full CPUs.  Not necessarily a good idea, but a relatively
> non-intrusive response to that particular error condition.

Given that we want the cpu only to run the user task I would think that is
not a good idea.

Thread

Re: clocksource_watchdog causing scheduling of timers every second  (was [v13] support "task_isolation" mode) Frederic Weisbecker <fweisbec@gmail.com> - 2016-08-11 00:20 +0200
  Re: clocksource_watchdog causing scheduling of timers every second  (was [v13] support "task_isolation" mode) Peter Zijlstra <peterz@infradead.org> - 2016-08-11 10:50 +0200
    Re: clocksource_watchdog causing scheduling of timers every second  (was [v13] support "task_isolation" mode) Frederic Weisbecker <fweisbec@gmail.com> - 2016-08-11 14:10 +0200
    Re: clocksource_watchdog causing scheduling of timers every second  (was [v13] support "task_isolation" mode) "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-08-12 00:30 +0200
      Re: clocksource_watchdog causing scheduling of timers every second  (was [v13] support "task_isolation" mode) Christoph Lameter <cl@linux.com> - 2016-08-12 01:10 +0200
        Re: clocksource_watchdog causing scheduling of timers every second  (was [v13] support "task_isolation" mode) "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-08-12 01:50 +0200
          Re: clocksource_watchdog causing scheduling of timers every second  (was [v13] support "task_isolation" mode) Christoph Lameter <cl@linux.com> - 2016-08-12 16:30 +0200
            Re: clocksource_watchdog causing scheduling of timers every second  (was [v13] support "task_isolation" mode) Frederic Weisbecker <fweisbec@gmail.com> - 2016-08-12 16:30 +0200
              Re: clocksource_watchdog causing scheduling of timers every second  (was [v13] support "task_isolation" mode) "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-08-12 18:20 +0200
                Re: clocksource_watchdog causing scheduling of timers every second  (was [v13] support "task_isolation" mode) Frederic Weisbecker <fweisbec@gmail.com> - 2016-08-13 17:40 +0200

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