Re: [Qemu-devel] [PATCH 0/3] target-arm: cache tbflags in CPUARMState

[Alex Bennée]

Paolo Bonzini <address@hidden> writes:

> Computing TranslationBlock flags is pretty expensive on ARM, especially
> 32-bit.  Because tbflags are computed on every tb lookup, it is not
> unlikely to see cpu_get_tb_cpu_state close to the top of the profile
> now that QHT makes the hash table much more efficient.
>
> However, most tbflags only change when the EL is switched or after
> MSR instructions.  Based on this observation, this series caches these
> tbflags in CPUARMState, resulting in a 10-15% speedup on 32-bit code.

Hi,

I'm starting to clear out my review queue but I notice these now longer
apply cleanly to master. Where you going to re-issue the series once
you'd addressed Peter's concerns?

My general comments are I think this is a good idea but my concern is
ensuring state changes get picked up and we don't end up with
inconsistent state between real and cached values. I still have the
scars from my last attempt to rationalise cpu.h pstate, aarch64,
uncached_cpsr and spsr!

Cheers,

--
Alex Bennée