the kernel patch in this directory implements RLIMIT_RT_CPU:
the maximum amount of CPU time RT tasks may use, in percent.
Defaults to 80%.

the execrtlim utility in this directory can be used to test
this new capability beyond the default setting, e.g.:

  ./execrtlim 10 10 /bin/bash

will spawn a new shell with RLIMIT_RT_CPU curr/max set to
10%/10%.

Properties of the RT-CPU rlimit:

 - if there's idle time in the system then RT tasks will be
   allowed to use more than the limit.

 - if an RT task goes above the limit all the time then there
   is no guarantee that exactly the limit will be allowed for
   it. (i.e. you should set the limit to somewhat above the real
   needs of the RT task in question.)

 - a zero RLIMIT_RT_CPU value means unlimited CPU time to that
   RT task.

 - a nonzero rt_cpu_limit value also has the effect of allowing
   the use of RT priorities to nonprivileged users.

 - on SMP the limit is measured and enforced per-CPU.

 - runtime overhead is minimal, especially if the limit is set to 0.

 - the CPU-use measurement code has a 'memory' of roughly 300 msecs.
   I.e. if an RT task runs 100 msecs nonstop then it will increase
   its CPU use by about 30%. This should be fast enough for users for
   the limit to be human-inperceptible, but slow enough to allow
   occasional longer timeslices to RT tasks.

have fun,

	Ingo