All of lore.kernel.org
 help / color / mirror / Atom feed
From: "Alex Bennée" <alex.bennee@linaro.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 0/3] target-arm: cache tbflags in CPUARMState
Date: Thu, 10 Nov 2016 11:42:30 +0000	[thread overview]
Message-ID: <87k2cb8st5.fsf@linaro.org> (raw)
In-Reply-To: <1473847013-20191-1-git-send-email-pbonzini@redhat.com>


Paolo Bonzini <pbonzini@redhat.com> 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

  parent reply	other threads:[~2016-11-10 11:42 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-14  9:56 [Qemu-devel] [PATCH 0/3] target-arm: cache tbflags in CPUARMState Paolo Bonzini
2016-09-14  9:56 ` [Qemu-devel] [PATCH 1/3] target-arm: introduce cpu_dynamic_tb_cpu_flags Paolo Bonzini
2016-09-14  9:56 ` [Qemu-devel] [PATCH 2/3] target-arm: add env->tbflags Paolo Bonzini
2016-09-26 22:00   ` Peter Maydell
2016-09-27  8:15     ` Paolo Bonzini
2016-09-14  9:56 ` [Qemu-devel] [PATCH 3/3] target-arm: cache most tbflags Paolo Bonzini
2016-09-26 10:04 ` [Qemu-devel] [PATCH 0/3] target-arm: cache tbflags in CPUARMState Laurent Desnogues
2016-09-26 11:13   ` Laurent Desnogues
2016-11-10 11:42 ` Alex Bennée [this message]
2016-11-10 12:19   ` Paolo Bonzini
2016-11-10 13:37     ` Alex Bennée

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=87k2cb8st5.fsf@linaro.org \
    --to=alex.bennee@linaro.org \
    --cc=pbonzini@redhat.com \
    --cc=qemu-devel@nongnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.