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

From: Alex Bennée
Subject: Re: [Qemu-devel] [PATCH 0/3] target-arm: cache tbflags in CPUARMState
Date: Thu, 10 Nov 2016 13:37:00 +0000
User-agent: mu4e 0.9.17; emacs

Paolo Bonzini <address@hidden> writes:

> On 10/11/2016 12:42, Alex Bennée wrote:
>> 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?
> Yes, I didn't want to send them two days before soft freeze and Peter's
> vacation. :)

Cool. Well I'll happily look at it while he's away as I think I need to
learn more about the flag mechanism anyway. Unless there are any
regressions that have come up during soft-freeze that I need to look at?

Alex Bennée

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