On Wed, Jun 24, 2015 at 07:50:42AM -0700, Paul E. McKenney wrote: > On Wed, Jun 24, 2015 at 09:35:03AM +0200, Peter Zijlstra wrote:
> > I still don't see a problem here though; the stop_one_cpu() invocation > > for the CPU that's suffering its preemption latency will take longer, > > but so what? > > > > How does polling and dropping back to sync_rcu() generate better > > behaviour than simply waiting for the completion? > > Because if there is too much delay, synchronize_rcu() is no slower > than is synchronize_rcu_expedited(), plus synchronize_rcu() is much > more efficient. Still confused.. How is polling and then blocking more efficient than just blocking in the first place? I'm seeing the polling as a waste of cpu time. The thing is, if we're stalled on a stop_one_cpu() call, the sync_rcu() is equally stalled. The sync_rcu() cannot wait more efficient than we're already waiting either. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
