Messages in this thread | | | Date | Sat, 27 May 2006 11:28:04 +1000 | From | Peter Williams <> | Subject | Re: [RFC 0/5] sched: Add CPU rate caps |
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Con Kolivas wrote: > On Friday 26 May 2006 14:20, Peter Williams wrote: >> These patches implement CPU usage rate limits for tasks. > > Nice :)
Thanks.
> >> Although the rlimit mechanism already has a CPU usage limit (RLIMIT_CPU) >> it is a total usage limit and therefore (to my mind) not very useful. >> These patches provide an alternative whereby the (recent) average CPU >> usage rate of a task can be limited to a (per task) specified proportion >> of a single CPU's capacity. The limits are specified in parts per >> thousand and come in two varieties -- hard and soft. > > Why 1000?
Probably a hang over from a version where the units were proportion of a whole machine. Percentage doesn't work very well if there are more than 1 CPU in that case (especially if there are more than 100 CPUs :-)). But it's also useful to have the extra range if your trying to cap processes (or users) from outside the scheduler using these primitives.
> I doubt that degree of accuracy is possible in cpu accounting and > accuracy or even required. To me it would seem to make more sense to just be > a percentage. >
It's not meant to imply accuracy :-). The main issue is avoiding overflow when doing the multiplications during the comparisons.
Peter -- Peter Williams pwil3058@bigpond.net.au
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