Messages in this thread | | | Date | Thu, 27 Jan 2005 09:59:47 +0100 | From | Ingo Molnar <> | Subject | Re: [patch, 2.6.11-rc2] sched: RLIMIT_RT_CPU_RATIO feature |
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* Ingo Molnar <mingo@elte.hu> wrote:
> negative nice levels are a guaranteed way to monopolize the CPU. > SCHED_FIFO with throttling could at most be used to 'steal' CPU time > up to the threshold. Also, if a task 'runs away' in SCHED_FIFO mode it > will be efficiently throttled. While if it 'runs away' in nice--20 > mode, it will take away 95+% of the CPU time quite agressively. > Furthermore, more nice--20 tasks will do much more damage (try thunk.c > at nice--20!), while more throttled SCHED_FIFO tasks only do damage to > their own class - the guaranteed share of SCHED_OTHER tasks (and > privileged RT tasks) is not affected.
furthermore, the current way of throttling SCHED_FIFO tasks that violate the limit makes it less likely that application writers would abuse the feature with CPU-intensive apps, because _if_ you violate the limit then the penalty is high. E.g. a blatant violation of the limit via a pure CPU loop ends up getting much less CPU time than even the limit would allow for. For audio/RT apps this is fine, because they must plan their CPU overhead anyway so they are a much more controlled environment and just do things properly to avoid the penalty.
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