Messages in this thread | | | From | Daniel Phillips <> | Subject | Re: [2.4.17/18pre] VM and swap - it's really unusable | Date | Mon, 14 Jan 2002 18:36:59 +0100 |
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On January 14, 2002 02:45 pm, yodaiken@fsmlabs.com wrote: > POSIX makes no specification of how scheduling classes interact - unless something changed > in the new version. > > But more than that, the problem of preemption is much more complex when you have > task that do not share the "goodness fade" with everything else. That is, given a > set of SCHED_OTHER processes at time T0, it is reasonable to design the scheduler so > that there is some D so that by time T0+D each process has become the highest priority > and has received cpu up to either a complete time slice or a I/O block. Linux kind of > has this property now, and I believe that making this more robust and easier to analyze > is going to be an enormously important issue. However, once you add SCHED_FIFO in the > current scheme, this becomes more complex. And with preempt, you cannot even offer the > assurance that once a process gets the cpu it will make _any_ advance at all.
So the prediction here is that SCHED_FIFO + preempt can livelock some set of correctly designed processes, is that it? I don't see exactly how that could happen, though that may simply mean I didn't read closely enough.
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