cpuset configuration and measurements for power management
vincent.guittot at linaro.org
Tue Aug 23 13:07:01 UTC 2011
On 23 August 2011 14:41, Daniel Lezcano <daniel.lezcano at linaro.org> wrote:
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> Hi all,
> I did the following cpuset configuration:
> if [ ! -d /sys/fs/cgroup ]; then
> echo "cgroup not supported by the kernel"
> 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)"
> # 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
> 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
> -- Daniel
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