On Sat, Dec 31, 2005 at 12:14:26PM -0800, Paul E. McKenney wrote:
> So it seems to me that Linus's patch is part of the solution, but
> needs to also have a global component, perhaps as follows:
>
> if (unlikely(rdp->count > 100)) {
> set_need_resched();
> if (unlikely(rdp->count - rdp->last_rs_count > 1000)) {
> int cpu;
>
> rdp->last_rs_count = rdp->count;
> spin_lock_bh(&rcu_bh_state.lock);
> for_each_cpu_mask(cpu, rdp->rcu_bh_state.cpumask)
> smp_send_reschedule(cpu);
> spin_unlock_bh(&rcu_bh_state.lock);
> }
> }
Yes, something like this that covers corner cases and forces
queiscent state in all cpus, would be ideal.
> I am sure that I am missing some interaction or another with tickless
> idle and CPU hotplug covered.
It would be safe to miss a cpu or two while sending the resched
interrupt. So, I don't think we need to worry about tickless
idle and cpu hotplug.
> There also needs to be some adjustment in rcu_do_batch(), which will
> have to somehow get back to a quiescent state periodically. Dipankar,
> Vatsa, thoughts?
My original thought was to make maxbatch dynamic and automatically
adjust it depending on the situation. I can try that approach.
Thanks
Dipankar
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