Cgroups, burst

Hey,

Is there an easy way to burst CPU resources with cgroups when needed?
For example I want to restrict 20% of CPU per process and for example
i want to allow process to use 100% of CPU for 30 sec (burst).

I mean i want restrict CPU usage at 20% per process, not per group.
Restrict resources per group I can do this way:

echo 10000 > cpu.cfs.quota_us
echo 50000 > cpu.cfs_period_us

But I want to restrict usage per process, and if there is a
possibility to burst it.

Or maybe is there a function that will indicate when app will consume
all resources? Then I will just switch her PID to another cgroup (that
will have 100% CPU) for 30 seconds and then back to previous cgroup.