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

[Laurent Desnogues <laurent.desnogues@gmail.com>]

Hello,

On Wed, Sep 14, 2016 at 11:56 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> 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.

I like that patch!

I quickly tested with some softmmu images on both AArch32 and AArch64
and I can confirm the speedup.

As far as your patch goes:

Tested-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Reviewed-by: Laurent Desnogues <laurent.desnogues@gmail.com>

Thanks,

Laurent

PS - BTW, I couldn't run any user mode program since they segfault on
mainline for some reason I have no time to look into.  The v2.7.0 tag
works.


> Paolo
>
> Paolo Bonzini (3):
>   target-arm: introduce cpu_dynamic_tb_cpu_flags
>   target-arm: add env->tbflags
>   target-arm: cache most tbflags
>
>  target-arm/cpu.c           |  2 ++
>  target-arm/cpu.h           | 58 ++++++++++++++++++++++++++++++++--------------
>  target-arm/helper.c        |  2 ++
>  target-arm/helper.h        |  1 +
>  target-arm/op_helper.c     |  7 ++++++
>  target-arm/translate-a64.c |  4 ++++
>  target-arm/translate.c     | 12 ++++++++--
>  target-arm/translate.h     |  1 +
>  8 files changed, 68 insertions(+), 19 deletions(-)
>
> --
> 2.7.4
>
>