Re: [RFC PATCH 0/6] target/ppc: Improve 4xx and 440 tlbwe

[BALATON Zoltan]

On Tue, 14 Nov 2023, Nicholas Piggin wrote:
> Well I split out these patches and looked a bit closer and added
> a few more things.
>
> I think it may be a bit too much to do the optimisations for
> this release, because 4xx TLB flushing has some quirks too so
> it's not just simple implementation of 4xx scheme in 440. We
> could try for next time.
>
> The bug fix patch 1 maybe we should do. We haven't been able to
> confirm it fixes anything but there was mention of occasional
> random crashes.

I did some quick testing of this series and found that patch 1 alone makes 
it slower but not known to fix any issue so I'd say don't commit just this 
patch without the rest. The current version works enoigh so we can live 
with that until the next version. With the other patches it's faster and 
the last patch does make a difference, it makes it a bit faster. I did not 
record the numbers and only did one measurement so it's only approximate 
but unless you plan to take the whole series now then keep patch 1 for 
next devel cycle as well.

Regards,
BALATON Zoltan

> Thanks,
> Nick
>
> Nicholas Piggin (6):
>  target/ppc: Fix 440 tlbwe TLB invalidation gaps
>  target/ppc: Factor out 4xx ppcemb_tlb_t flushing
>  target/ppc: 4xx don't flush TLB for a newly written software TLB entry
>  target/ppc: 4xx optimise tlbwe_lo TLB flushing
>  target/ppc: 440 optimise tlbwe TLB flushing
>  target/ppc: optimise ppcemb_tlb_t flushing
>
> target/ppc/mmu_helper.c | 105 +++++++++++++++++++++++-----------------
> 1 file changed, 61 insertions(+), 44 deletions(-)