[RESEND RFC PATCH v1 5/5] arm64/mm: Elide tlbi in contpte_convert() under BBML2

[Will Deacon]

On Wed, Dec 11, 2024 at 04:01:41PM +0000, Mikołaj Lenczewski wrote:
> If we support BBM level 2, we can potentially avoid an intermediate
> TLB invalidation, as hardware is capable of managing the TLB itself
> in this situation. Hardware will either silently clear out the
> offending entry, or will take a TLB Conflict Abort Exception.
> 
> Note that such aborts should not occur on Arm hardware and indeed
> were not seen on any of the benchmarked systems.
> 
> Eliding the invalidation results in a 12% improvement on a
> microbenchmark which targeted the worst case of contpte_convert(), which
> represents an 80% reduction in the overhead of contpte_convert().

Can you run something more indicative of real world performance than a
targetted microbenchmark please?

Will