Index of /mingo/rt-limit-patches/older

      Name                    Last modified       Size  Description


[DIR] Parent Directory        27-Jan-2005 03:48      -  
[   ] rt-limit-2.6.11-rc2-B4  24-Jan-2005 08:27     8k  
[   ] rt-limit-2.6.11-rc2-D4  25-Jan-2005 09:20     6k  
[   ] rt-limit-2.6.11-rc2-D5  26-Jan-2005 02:03     6k  
[   ] rt-limit-2.6.11-rc2-D6  26-Jan-2005 04:17    10k  
[   ] rt-limit-2.6.11-rc2-D7  26-Jan-2005 04:55    10k  


this patch adds the /proc/sys/kernel/rt_cpu_limit tunable: the maximum
amount of CPU time all RT task smay use, in percent. Defaults to 80%.

properties of rt_cpu_limit:

 - if there's idle time in the system then RT tasks will be
   allowed to use more than the limit. Once SCHED_OTHER tasks
   are present again, the limit is enforced.

 - 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.)

 - zero rt_cpu_limit value means unlimited CPU time to all
   RT tasks.

 - a nonzero rt_cpu_limit value also has the effect of allowing
   the use of RT scheduling classes/priorities for nonprivileged
   users. I.e. a value of 100% differs from a value of 0 in that 0
   doesnt allow RT priorities for ordinary 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