I would try the cgroups mailing list: http://vger.kernel.org/vger-lists.html#cgroups Juan. On Tue, Sep 20, 2016 at 2:39 PM, Rahul Bhattacharya <rahulimpdocs@gmail.com> wrote:
Any idea or feedback for the person to contact? Thanks
br rb
On Wed, Sep 14, 2016 at 5:21 PM, Rahul Bhattacharya <rahulimpdocs@gmail.com> wrote:
When I try to move a RT task to a different cgroup(shown below) I get a EINVAL error.
However I can change the cgroup first and then change the sched policy.
After looking into kernel source code(I dont use CONFIG_RT_GROUP_SCHED config) I was able to extract this piece of logic
chrt -p 777 pid 777's current scheduling policy: SCHED_OTHER pid 777's current scheduling priority: 0
cat /proc/777/cgroup 2:cpu,cpuacct:/system.slice 1:name=systemd:/system.slice/d.service
chrt -f -p 50 777
root@mgu-high:~# chrt -p 777 pid 777's current scheduling policy: SCHED_FIFO pid 777's current scheduling priority: 50
/bin/echo 777>/sys/fs/cgroup/cpu,cpuacct/interaction.slice/tasks echo: write error: Invalid argument
After browsing kernel sources I was able to find out the reason of failure.
static int cpu_cgroup_can_attach(struct cgroup_subsys_state *css, struct cgroup_taskset *tset) { struct task_struct *task;
cgroup_taskset_for_each(task, tset) { #ifdef CONFIG_RT_GROUP_SCHED if (!sched_rt_can_attach(css_tg(css), task)) return -EINVAL; #else /* We don't support RT-tasks being in separate groups */ if (task->sched_class != &fair_sched_class) { return -EINVAL; } #endif } return 0; }
My question is why is this check required? Also, changing cgroups first and then the policy of FIFO works without issue(?) for the task.
Thanks
br
rb
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-- Juan-Luis de Sousa-Valadas Castaño Iberia Infrastructure Consultant - Red Hat