On 16 December 2011 01:58, Suresh Siddha <suresh.b.sid...@intel.com> wrote: > On Thu, 2011-12-15 at 05:36 -0800, Vincent Guittot wrote: >> I'm using cyclictest to easily reproduce the problem on my dual cortex-A9 > > So does the cyclictest itself exhibit the problem or running cyclictest > with another workload showed the problem? In other words, what numbers > of the workload did you see change with this patch? >
Using a cyclictest -q -t 5 -D 4 on my dual cortex-A9 shows the fact that the softirqs timer and sched are not called very often and the cpu_power is nearly never updated. I have also used the following sequence : cyclictest -q -t 5 -D 4 & sleep 2 cyclictest -q -t 3 --affinity=0 -p 99 -D 2 The cpu_power of cpu0 should start to decrease when the rt threads are started. Without the patch, we must wait for the next sched softirq for starting to update the cpu_power and we have no guarantee of the maximum interval. With the patch, the cpu_power is updated regularly using the balance_interval value. Vincent >> >> > Then again, its probably easier to keep update_group_power on this_cpu >> > than to allow a remote update of your cpu_power. >> > >> >> This additional path for updating the cpu_power will only be used by >> this_cpu because it is called by idle_balance. But we still have a >> call to update_group_power by a remote cpu when nohz_idle_balance is >> called. > > As Vincent mentioned, the current mainline kernel already updates the > remote cpu's group_power in the nohz idle load balancing patch. > > Also with all the recent nohz idle load balancing using kick, on a > dual-core system there may not be any nohz idle load balancing if > multiple tasks wakeup, run for short time and go back to idle before the > next tick. We rely on the wakeup balance to get it right in this case. > > thanks, > suresh > _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
