Docker CPU share metrics


Is there any metric in either mesos input or docker input that gives the cpushares allocated to the container? The output of docker inspect gives below (part of the output)
"CpuShares": 409,
I am trying to get the total CPUs allocated in a mesos-slave node. mesos_slave_cpus_used does not give the correct value and looks like it give the current usage and not the allocated value.
I tried the docker input cpu metrics but was not able to find the shares allocated. any suggestions?