Messages in this thread |  | | | Date | Tue, 2 Sep 2008 08:18:06 +0200 | | From | Andi Kleen <> | | Subject | Re: [PATCH, RFC, tip/core/rcu] v3 scalable classic RCU implementation |
> > It would be better if you hung rcu_irq_enter in the irq_enter() if
> > statement that checks if the task was idle or not. This way it would
> > be zero overhead for interruptions of non busy CPUs, keeping
Sorry that should have been "non idle CPUs" of course.
> > it out of many fast paths.
> >
> > Haven't read everything, sorry.
>
> So that I lose the #else above, and so that irq_enter() and irq_exit()
> look something like the following (with additional adjustments to suit)?
Yes looks good.
BTW I wonder if the compiler CSEs the idle_cpu() check properly.
> void irq_enter(void)
> {
> #ifdef CONFIG_NO_HZ
> int cpu = smp_processor_id();
> if (idle_cpu(cpu) && !in_interrupt())
> tick_nohz_stop_idle(cpu);
> #endif
> __irq_enter();
> #ifdef CONFIG_NO_HZ
> if (idle_cpu(cpu)) {
> rcu_irq_enter();
> tick_nohz_update_jiffies();
> }
> #endif
-Andi
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