Messages in this thread | | | Date | Fri, 28 Jan 2000 18:41:36 +0100 | From | Michael Schulz <> | Subject | Re: Strange scheduling behavoir in SMP (kernel 2.2.14) |
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Stephen C. Tweedie: > Umm, what CPU is X going to run on in that case? > > You have two high-priority, interactive tasks to be scheduled: X and > xosview. You have one low-priority background task --- the > benchmark. If both xosview and X are ever runnable at the same time, > then the benchmark task MUST be bumped off the cpu. And if the other > cpu becomes free first, then what are you going to do? Leave it idle? > That may win in some cases but in general it's a bad idea to bet that > way. Yes. We certanly have to take the whole box into account. Especially when doing benchmarks (boot into a shell...)
But the point is: where have processes been scheduled the first time. Let's say X started on cpu0 and has a strong tendency to stay there. Somehow xosview made it to the same cpu0 after a wile. That could be the outcome because the benchmark tends to be more active and xosview more sleepy. Or whatever other constraints could influence process migration and scheduling.
In fact it is a matter of balancing all constraints in a reasonable way. There is no systematic way to achieve an optimal balance. You can only try out different settings. Or invent new constraints which grab a specific situation of the box in case the once we have aren't enuf. These things are very fragile, but...
Micha.
-- -- Michael Schulz, NatS - Uni Hamburg
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