Hi Peter, Does it sound good for you if I update the comment of this patch with the explanation of the previous mails or do you need more information ?
Thanks, Vincent On 16 December 2011 09:23, Vincent Guittot <vincent.guit...@linaro.org> wrote: > 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
