Messages in this thread | | | Date | Tue, 3 Jan 2006 19:39:42 +0530 | From | Dipankar Sarma <> | Subject | Re: [patch] latency tracer, 2.6.15-rc7 |
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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.
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