Chen, Kenneth W wrote:
Nick Piggin wrote on Tuesday, March 21, 2006 11:30 PM
Well mmu_gather uses a per-cpu data structure and is non preemptible,
which I guess is one of the main reasons why we have this preemption
here.
You're right that another good reason would be ptl lock contention,
however I don't think that alleviating that problem alone would allow
longer mmu_gather scheduling latencies, because the longest latency
is still the mmu_gather <--> mmu_finish span.
OK, I think it would be beneficial to take a latency measurement again,
just to see how it perform now a day. The dynamics might changed.
Well I wouldn't argue against further investigation or fine tuning
the present code, however also remember that the way of unconditionally
finishing the mmu_gather that the patch is aimed to prevent never
actually lowered ptl hold times itself.
--
SUSE Labs, Novell Inc.
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