[PATCH 4/7] powerpc: Free up four 64K PTE bits in 64K backed HPTE pages

[Ram Pai]

On Thu, Sep 14, 2017 at 06:13:57PM +1000, Benjamin Herrenschmidt wrote:
> On Fri, 2017-09-08 at 15:44 -0700, Ram Pai wrote:
> > The second part of the PTE will hold
> > (H_PAGE_F_SECOND|H_PAGE_F_GIX) at bit 60,61,62,63.
> > NOTE: None of the bits in the secondary PTE were not used
> > by 64k-HPTE backed PTE.
> 
> Have you measured the performance impact of this ? The second part of
> the PTE being in a different cache line there could be one...

hmm..missed responding to this comment.

I did a preliminay measurement running mmap bench in the selftest.
Ran it multiple times. almost always the numbers were either equal-to
or better-than without the patch-series.

RP