Messages in this thread | | | Date | Wed, 22 Mar 2006 15:52:59 +1100 | From | Nick Piggin <> | Subject | Re: [PATCH] less tlb flush in unmap_vmas |
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Shaohua Li wrote:
>In unmaping region, if current task doesn't need reschedule, don't do a >tlb_finish_mmu. This can reduce some tlb flushes. > >In the lmbench tests, this patch gives 2.1% improvement on exec proc >item and 4.2% on sh proc item. > >
The problem with this is that by the time we _do_ determine that a reschedule is needed, we might have built up a huge amount of work to do (which can probably be as much if not more exensive per-page as the unmapping), so scheduling latency can still be unacceptable so I'm afraid I don't think we can include this patch.
One option I've been looking into is my "mmu gather in-place" that never needs extra tlb flushes and is always preemptible... so that may be a way forward.
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