On Wednesday 06 August 2003 22:28, Rob Landley wrote:
>> So, how does SCHED_SOFTRR fail? Theoretically there is a minimum timeslice
>> you can hand out, yes? And an upper bound on scheduling latency. So
>> logically, there is some maximum number "N" of SCHED_SOFTRR tasks running
>> at once where you wind up round-robining with minimal timeslices and the
>> system is saturated. At N+1, you fall over. (And in reality, there are
>> interrupts and kernel threads and other things going on that get kind of
>> cramped somewhere below N.)
On Thu, Aug 07, 2003 at 04:42:55PM +0100, Daniel Phillips wrote:
> The upper bound for softrr realtime scheduling isn't based on number
> of tasks, it's a global slice of cpu time: so long as the sum of
> running times of all softrr tasks in the system lies below limit,
> softrr tasks will be scheduled as SCHED_RR, otherwise they will be
> SCHED_NORMAL.
You're thinking of Little's law, which is describes the mean number of
waiters on a queue as the mean service time divided by the number of
servers times the mean inter-arrival time.
-- wli
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