Re: [PATCH] Load balancing problem in 2.6.2-mm1

[Martin J. Bligh]

>> It's the classic fairness vs throughput thing we've argued about before.
>> Most workloads don't have that static a number of processes, but it 
>> probably does need to do it if the imbalance is persistent ... but much
>> more reluctantly than normal balancing. See the patch I sent out a bit
>> earlier to test it - that may be *too* extreme in the other direction,
>> but it should confirm what's going on, at least.
> 
> Yep. I've argued for fairness here, and that is presently what
> we get. Between nodes the threshold should probably be higher
> though.

OK, but do you agree that the rate we rebalance things like 2 vs 1 should
be slower than the rate we rebalance 3 vs 1 ? Fairness is only relevant
over a long term imbalance anyway, so there should be a big damper on
"fairness only" rebalances.

Moreover, as Rick pointed out, it's particularly futile over idle cpus ;-)

m.

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