On Sat, 21 Mar 2009 22:18:22 -0700 "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx> wrote: > > I'm measuring the time that the following code takes: > > > > init_completion(&rcu.completion); > > /* Will wake me after RCU finished. */ > > call_rcu(&rcu.head, wakeme_after_rcu); > > /* Wait for it. */ > > wait_for_completion(&rcu.completion); > > > > No, my confusion -- I misread as 2700 milliseconds rather than 2700 > -microseconds-. 2700 microseconds (or 2.7 milliseconds) is in the > expected range for synchronize_rcu() on an HZ=1000 system. 2.7 > seconds would of course be way out of line. > > > If the former, exactly which kernel are you using? The single-CPU > > > optimization was added in 2.6.29-rc7, commit ID a682604838. > > > > a bit after -rc8, specifically commit > > 5bee17f18b595937e6beafeee5197868a3f74a06 > > How many synchronize_rcu() calls are you seeing on the boot path? I see 20 that hit the above code path (eg ones that wait) until userspace starts. > Also, are you running with NO_HZ=y? of course... is there any other way ? ;-) -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
