Re: [PATCH 19/32] nohz/cpuset: Restart tick when nohz flag is cleared on cpuset

Frederic Weisbecker
2011-08-30T15:10:51Z

On Mon, Aug 29, 2011 at 06:02:01PM +0200, Peter Zijlstra wrote:
> On Mon, 2011-08-15 at 17:52 +0200, Frederic Weisbecker wrote:
> > +++ b/kernel/cpuset.c
> > @@ -1199,6 +1199,14 @@ static void cpuset_change_flag(struct task_struct *tsk,
> >
> > DEFINE_PER_CPU(int, cpu_adaptive_nohz_ref);
> >
> > +static void cpu_exit_nohz(int cpu)
> > +{
> > + preempt_disable();
> > + smp_call_function_single(cpu, cpuset_exit_nohz_interrupt,
> > + NULL, true);
> > + preempt_enable();
> > +}
> > +
> > static void update_nohz_cpus(struct cpuset *old_cs, struct cpuset *cs)
> > {
> > int cpu;
> > @@ -1212,6 +1220,19 @@ static void update_nohz_cpus(struct cpuset *old_cs, struct cpuset *cs)
> > per_cpu(cpu_adaptive_nohz_ref, cpu) += 1;
> > else
> > per_cpu(cpu_adaptive_nohz_ref, cpu) -= 1;
> > +
> > + val = per_cpu(cpu_adaptive_nohz_ref, cpu);
> > +
> > + if (!val) {
> > + /*
> > + * The update to cpu_adaptive_nohz_ref must be
> > + * visible right away. So that once we restart the tick
> > + * from the IPI, it won't be stopped again due to cache
> > + * update lag.
> > + */
> > + smp_mb();
> > + cpu_exit_nohz(cpu);
> > + }
> > }
> > }
> > #else
> > diff --git a/kernel/sched.c b/kernel/sched.c
> > index 78ea0a5..75378be 100644
> > --- a/kernel/sched.c
> > +++ b/kernel/sched.c
> > @@ -2513,6 +2513,14 @@ void cpuset_update_nohz(void)
> > cpuset_nohz_restart_tick();
> > }
> >
> > +void cpuset_exit_nohz_interrupt(void *unused)
> > +{
> > + if (!tick_nohz_adaptive_mode())
> > + return;
> > +
> > + cpuset_nohz_restart_tick();
> > +}
>
> You do this just to annoy me, right? Why doesn't it live in cpuset.c
> where you use it?

Right, I'll move all those things and fix the naming / namespace.