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Subjectreschedule_idle changes in ac kernels
I just noticed the changes to reschedule_idle() in the 2.4.5-ac
kernel. I suspect these are the changes made for:

o Fix off by one on real time pre-emption in scheduler

I'm curious if anyone has ran any benchmarks before and after
applying this fix.

The reason I ask is that during the development of my multi-queue
scheduler, I 'accidently' changed reschedule_idle code to trigger
a preemption if preemption_goodness() was greater than 0, as
opposed to greater than 1. I believe this is the same change made
to the ac kernel. After this change, we saw a noticeable drop in
performance for some benchmarks.

The drop in performance I saw could have been the result of a
combination of the change, and my multi-queue scheduler. However,
in any case aren't we now going to trigger more preemptions?

I understand that we need to make the fig to get the realtime
semantics correct, but we also need to be aware of performance in
the non-realtime case.

Mike Kravetz
IBM Linux Technology Center
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