On Wed 24-10-12 11:44:17, Qiang Gao wrote:

On Wed, Oct 24, 2012 at 1:43 AM, Balbir Singh [off-list ref] wrote:

quoted

On Tue, Oct 23, 2012 at 3:45 PM, Michal Hocko [off-list ref] wrote:

quoted

On Tue 23-10-12 18:10:33, Qiang Gao wrote:

quoted

On Tue, Oct 23, 2012 at 5:50 PM, Michal Hocko [off-list ref] wrote:

quoted

On Tue 23-10-12 15:18:48, Qiang Gao wrote:

quoted

This process was moved to RT-priority queue when global oom-killer
happened to boost the recovery of the system..

Who did that? oom killer doesn't boost the priority (scheduling class)
AFAIK.

quoted

but it wasn't get properily dealt with. I still have no idea why where
the problem is ..

Well your configuration says that there is no runtime reserved for the
group.
Please refer to Documentation/scheduler/sched-rt-group.txt for more
information.

[...]

quoted

maybe this is not a upstream-kernel bug. the centos/redhat kernel
would boost the process to RT prio when the process was selected
by oom-killer.

This still looks like your cpu controller is misconfigured. Even if the
task is promoted to be realtime.

Precisely! You need to have rt bandwidth enabled for RT tasks to run,
as a workaround please give the groups some RT bandwidth and then work
out the migration to RT and what should be the defaults on the distro.

Balbir

see https://patchwork.kernel.org/patch/719411/

The patch surely "fixes" your problem but the primary fault here is the
mis-configured cpu cgroup. If the value for the bandwidth is zero by
default then all realtime processes in the group a screwed. The value
should be set to something more reasonable.
I am not familiar with the cpu controller but it seems that
alloc_rt_sched_group needs some treat. Care to look into it and send a
patch to the cpu controller and cgroup maintainers, please?

-- 
Michal Hocko
SUSE Labs

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