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

From: Paul E. McKenney
Date: Fri Aug 12 2016 - 12:19:34 EST


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