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


From: BALATON Zoltan
Subject: Re: [RFC PATCH 0/6] target/ppc: Improve 4xx and 440 tlbwe
Date: Wed, 15 Nov 2023 21:16:54 +0100 (CET)

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(-)





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