Messages in this thread | | | Date | Tue, 3 Jan 2006 07:55:46 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [patch] latency tracer, 2.6.15-rc7 |
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On Tue, Jan 03, 2006 at 07:39:42PM +0530, Dipankar Sarma wrote: > 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.
OK, does that also mean that the spin_lock_bh/spin_unlock_bh are also unnecessary? ;-)
> > 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.
Makes sense to me!
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