Re: [PATCH] less tlb flush in unmap_vmas

[Nick Piggin]

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.

---

Send instant messages to your online friends http://au.messenger.yahoo.com 
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/