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SubjectRe: Scheduler fairness problem on 2.6 series (Attn: Nick Piggin and others)
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Con Kolivas wrote:
| I tried this on the latest staircase patch (7.I) and am not getting any
| output from your script when tested up to 60 threads on my hardware. Can
| you try this version of staircase please?
| There are 7.I patches against 2.6.8-rc4 and 2.6.8-rc4-mm1


I just updated to 2.6.8-rc4-ck2 and tried the two options interactive
and compute. Is the compute stuff functional? I tried setting it to 1
within X and after that X wasn't usable anymore (meaning it looked like
locked up, frozen/gone mouse cursor even). I managed to switch back to
console and set it to 0 and all was OK again.

The interactive to 0 setting helped me with runnign locally multiple
processes using mpi. Nevertheless (only with interactive 1 regression to
vanilla scheduler, else same) can't this be enhanced?

Details: I am working on a load balancing class using mpi. For testing
purpises I am running multiple processes on my machine. So for a given
problem I can say, it needs x time to solve. Using more processes opn a
single machine, this time (except communication and balancing overhead)
shouldn't be much larger. Unfortunately this happens. Eg. a given
probelm using two processes needs about 20 seconds to finish. But using
8 it already needs 47s (55s with interactiv set to 1). No, my balancing
framework is quite good. On a real (small, even larger till 128 nodes
tested) cluster overhead is just as low as 3% to 5%, ie. it scales quite

Any idea how to tweak the staircase to get near the 20 seconds with more
processes? Or is this rather a problem of mpich used locally?

If you like I can send you my code to test (beware it is not that small).


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