On Tue, Aug 23, 2011 at 6:07 AM, Vincent Guittot <vincent.guit...@linaro.org> wrote: > On 23 August 2011 14:41, Daniel Lezcano <daniel.lezc...@linaro.org> wrote: >> -----BEGIN PGP SIGNED MESSAGE----- >> Hash: SHA1 >> >> >> Hi all, >> >> I did the following cpuset configuration: >> >> if [ ! -d /sys/fs/cgroup ]; then >> echo "cgroup not supported by the kernel" >> else >> mount -t cgroup cgroup /sys/fs/cgroup >> >> # needed to have the cgroup values inherited from >> # the parent cgroup >> echo 1 > /sys/fs/cgroup/cgroup.clone_children >> >> # create an empty cgroup 'cpu0' >> mkdir /sys/fs/cgroup/cpu0 >> >> # create an empty cgroup 'cpu1' >> mkdir /sys/fs/cgroup/cpu1 >> >> # assign cpu number '0' for cgroup cpu0 >> echo 0 > /sys/fs/cgroup/cpu0/cpuset.cpus >> >> # move outself to this new cgroup >> echo $$ > /sys/fs/cgroup/cpu0 >> >> # move all the tasks to the cpu0 cgroup >> # kernel threads won't be moved, don't worry about the >> # the errors. >> for i in $(cat /sys/fs/cgroup/tasks); do >> echo $i > /sys/fs/cgroup/cpu0/tasks || echo "failed to >> add pid $i/$(cat /proc/$i/comm)" >> done >> >> # assign a cpu for cgroup cpu1 >> echo 1 > /sys/fs/cgroup/cpu1/cpuset.cpus >> >> # make cpu1 exclusive so processes belonging >> # to the other cgroups won't be able to use it. >> echo 1 > /sys/fs/cgroup/cpu1/cpuset.cpu_exclusive >> fi >> >> >> At this point, most of the processes have been moved to the 'cpu0' >> cgroup and will use the cpu0 only. That does not prevent the cpu1 to be >> used by the kernel threads. Any application launched will run on cpu0 only. >> >> After running 10 infinite loops, the cpu accounting gives: >> >> cat /sys/fs/cgroup/cpu0/cpuacct.usage_percpu >> 418943579549 0 >> >> cat /sys/fs/cgroup/cpu1/cpuacct.usage_percpu >> 0 0 >> >> But the system is: >> >> cat /sys/fs/cgroup/cpuacct.usage_percpu >> 456741213041 30734572583 >> > > You should get the values before and after your tests and compute the > difference. You should also read value of /sys/fs/cgroup/ level where > we still have kernel threads if i have understand your comments > >> My guess is that reflects the kernel booted with the two cpus before we >> created the cgroup. I am investigation the 'isolcpus' kernel parameter. >> >> I think it is a good starting point to do some consumption measurements. >> >> Mike, Vincent, what do you think ? Do you need more informations or >> anything else ? >> > > Yes it's a good starting point. One key point will be to be sure to > not use cpu1. In fact, we mainly have 2 power efficient states: use > equally the 2 cpus or use only one cpu and put the other one in a low > power state.
This is true. I did some rough power measurements last week using an almost identical method to Daniel's and for a typical MP3 playback (display off, no UI) I saw very little improvement on current draw from the battery versus the same test without cpuset trickery. I think Daniel's stuff is a great start and many many more measurements must be done to get anywhere conclusive, but reducing auxillary CPU wake-ups is critical to getting this method to work. Regards, Mike > Vincent > >> Thanks >> -- Daniel >> >> - -- >> <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs >> >> Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | >> <http://twitter.com/#!/linaroorg> Twitter | >> <http://www.linaro.org/linaro-blog/> Blog >> >> -----BEGIN PGP SIGNATURE----- >> Version: GnuPG v1.4.11 (GNU/Linux) >> Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ >> >> iQEcBAEBAgAGBQJOU6AVAAoJEAKBbMCpUGYAbQoH/0NeKLecIuMT57B/w1Jid/bn >> yzqD3zwMt0EfUwfsU6H5dAYgumMzKmWWXR9+7FvYhkcckXfzumiMLFKhIybrUSz/ >> LW7ymHwxXcHWqBTKwMCasHzo9WhlRTlLA1pGAqo0qtG1IBpalE68ZRwItdY/HSOw >> 0mDGoegq4DHQtcF64XwGRZJo2wAsamtlWGejFdqLQU4FONyYI42rLXMNAG6VD3vG >> CJrIudH5hLz3ZBdHYeRB6kWaj1O4skAW6fgySASiqFWoEaZzvT/7UuVBEYawpuyT >> Pm+U9OHAfHUWfnyDASFfx6ZQKRS5Uk40XzThjGgwoo598EN8FXZD3N6UZ1WmL2U= >> =H00Z >> -----END PGP SIGNATURE----- >> > _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
