On Wed, Dec 17, 2014 at 2:08 AM, Will Deacon <will.deacon@arm.com> wrote:
>
> I think there are a couple of things you could try to see if that 2% comes
> back:
>
>   * Revert the patch and try the one here [1] instead (which only does part
>     (1) of the above).
>
> -- or --
>
>   * Instead of adding the tlb->end check to tlb_flush_mmu, add it to
>     tlb_flush_mmu_free

or just move the check back to tlb_flush_mmu() where it belongs.

I don't see why you moved it to "tlb_flush_mmu_tlbonly()" in the first
place, or why you'd now want to add it to tlb_flush_mmu_free().

Both of those helper functions have two callers:

 - tlb_flush_mmu(). Doing it here (instead of in the helper functions)
is the right thing to do

 - the "force_flush" case: we know we have added at least one page to
the TLB state so checking for it is pointless.

So I'm not seeing why you wanted to do it in tlb_flush_mmu_tlbonly(),
and now add it to tlb_flush_mmu_free(). That seems bogus.

So why not just this trivial patch, to make the logic be the same it
used to be (just using "end > 0" instead of the old "need_flush")?

                           Linus