Re: [PATCH 5/8] nohz: Restart the tick from irq exit

[Frederic Weisbecker]

On Fri, Jun 12, 2015 at 09:32:45AM +0200, Peter Zijlstra wrote:
> On Thu, Jun 11, 2015 at 07:36:05PM +0200, Frederic Weisbecker wrote:
> > Restart the tick when necessary from the irq exit path. It makes nohz
> > full more flexible and allow it to piggyback the tick restart on the
> > scheduler IPI in the future instead of sending a dedicated IPI that
> > often doubles the scheduler IPI on task wakeup. This will require
> > careful review of resched_curr() callers.
> 
> This seems to assume schedule_ipi() callers use irq_exit(), this is
> false.

Indeed there will be that too. Note the current patch doesn't yet rely on
schedule_ipi(), we are still using the nohz ipis. But introducing the
tick restart on irq exit prepares for later piggybacking on scheduler_ipi().

I think this will involve changes on got_nohz_idle_kick(), renamed to
got_nohz_kick() and include nohz full related checks to trigger the
irq_enter()/exit() pair.
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