[lxc-users] Enabling real time support in containers

[Peter Steele]

> We have a need to create real time threads in some of our processes 
> and I've been unable to configure an LXC container to support this. 
> One reference I came across was to set a container's real time 
> bandwidth via the lxc.cgroup.cpu.rt_runtime_us parameter in its config 
> file:
>
> lxc.utsname = test01
> lxc.include = /var/lib/lxc/centos.conf
> lxc.network.veth.pair = test01
> lxc.network.hwaddr = fe:d6:e8:e2:fa:db
> lxc.rootfs = /var/lib/lxc/test01/rootfs
> lxc.rootfs.backend = dir
> lxc.cgroup.cpuset.cpus = 0,1
> lxc.cgroup.memory.limit_in_bytes = 2097152000
> lxc.cgroup.memory.memsw.limit_in_bytes = 3170893824
> lxc.cgroup.cpu.rt_runtime_us = 475000
>
> This container starts up fine if lxc.cgroup.cpu.rt_runtime_us is 0 
> (zero). Anything other than 0 is rejected, which means real time 
> threads cannot be created in this container.
>
> What am I missing to get this to work? I am using lxc version 2.0.6 
> under CentOS 7.2. The container is being created using a custom CentOS 
> 7.2 image.

No takers on this? I assume this is possible? I'm looking for the 
configuration options that would allow code such as this to run :

     pthread_attr_setinheritsched(&tattr, PTHREAD_EXPLICIT_SCHED);
     pthread_attr_setschedpolicy(&tattr, SCHED_FIFO);
     tsparam.sched_priority = sched_get_priority_max(SCHED_FIFO) - 7;
     pthread_attr_setschedparam(&tattr, &tsparam);
     rc = pthread_create(&test_thread, &tattr, test, NULL);

While this code runs fine in my host, it returns a non-zero code on my 
containers, indicating I am not allowed to create real time threads. I'm 
assuming this is a configuration issue in my LXC containers since I've 
seen this same code run under other container frameworks. There doesn't 
seem to be a lot of hits on this topic though when it comes to LXC.

Peter