Messages in this thread | | | Date | Fri, 7 Apr 2006 02:23:59 -0700 | Subject | Re: RT task scheduling | From | Bill Huey (hui) <> |
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On Wed, Apr 05, 2006 at 08:25:04PM -0700, Darren Hart wrote: > Part of the issue here is to define what we consider "correct behavior" for > SCHED_FIFO realtime tasks. Do we (A) need to strive for "strict realtime > priority scheduling" where the NR_CPUS highest priority runnable SCHED_FIFO > tasks are _always_ running? Or do we (B) take the best effort approach with > an upper limit RT priority imbalances, where an imbalance may occur (say at > wakeup or exit) but will be remedied within 1 tick. The smpnice patches > improve load balancing, but don't provide (A).
I regret getting into this discussion late, but it should always be (A) if you're building a kernel for strict RT usage. (B) is for a system that's more general purpose. It's not a "one policy fits all" kind of problem.
The search costs of (A) could be be significant and may degrade system performance. Optimizations for that case is for another discussion.
bill
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