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

From "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Newsgroups linux.kernel
Subject Re: clocksource_watchdog causing scheduling of timers every second (was [v13] support "task_isolation" mode)
Date 2016-08-12 18:20 +0200
Message-ID <s5nlD-3VR-9@gated-at.bofh.it> (permalink)
References (5 earlier) <s56Ea-1t7-11@gated-at.bofh.it> <s57gS-25e-25@gated-at.bofh.it> <s57Tz-2lF-17@gated-at.bofh.it> <s5lDc-2Nj-29@gated-at.bofh.it> <s5lDc-2Nj-31@gated-at.bofh.it>
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On Fri, Aug 12, 2016 at 04:26:13PM +0200, Frederic Weisbecker wrote:
> On Fri, Aug 12, 2016 at 09:23:13AM -0500, Christoph Lameter wrote:
> > On Thu, 11 Aug 2016, Paul E. McKenney wrote:
> > 
> > > Heh!  The only really good idea is for clocks to be reliably in sync.
> > >
> > > But if they go out of sync, what do you want to do instead?
> > 
> > For a NOHZ task? Write a message to the syslog and reenable tick.

Fair enough!  Kicking off a low-priority task would achieve the latter
but not necessarily the former.  And of course assumes that the worker
thread is at real-time priority with various scheduler anti-starvation
features disabled.

> Indeed, a strong clocksource is a requirement for a full tickless machine.

No disagrement here!  ;-)

							Thanx, Paul

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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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