Re: [PATCH v5 6/7] x86/tlb: optimizing flush_tlb_mm

[Nick Piggin]

On 15 May 2012 20:00, Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> wrote:
> On Tue, 2012-05-15 at 19:52 +1000, Nick Piggin wrote:
>>
>> It could be warranted to change tlb_flush_mmu to a range API to
>> avoid doing the per-entry tracking which those architectures do?
>
> The per-entry could result in a much smaller range, there's no point in
> flushing tlbs for unpopulated pages.

Well common case for small ranges hopefully would be quite dense
I think. It could be not worth the extra work (although maybe it would
be).

>
> Anyway, I don't think even think we'd need to change the API for that,
> you could track the entire range through tlb_start_vma() if you wanted
> (although nobody does that IIRC).

I'm not sure if you can do that very well, because the tlb might have to
be flushed part way through a vma when we fill up the gather, so you
don't want to flush the full range each time.
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