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From: Richard Henderson <richard.henderson@linaro.org>
To: Owen Anderson <oanderso@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org
Subject: Re: [RFC] Don't lookup full CPU state in the indirect branch fast path on AArch64 when running in user mode.
Date: Mon, 19 Oct 2020 15:58:36 -0700	[thread overview]
Message-ID: <942d4ac4-e624-11f6-f3c8-28d64ab568d5@linaro.org> (raw)
In-Reply-To: <CAKs3XfKMpTaAO6vj-V--zp_zY_Jm9HKkgkpCbCCKCQHSDT8y3g@mail.gmail.com>

On 10/19/20 3:44 PM, Owen Anderson wrote:
> My use case is currently using QEMU 4.0, but we will be moving to QEMU
> 4.2 soon.  I do not have --enable-tcg-debug enabled.
> e979972a6a1 does look promising, and like it might deliver increased
> performance for our use case. It looks like the code in 4.0 is doing a
> lot more work gathering the flags values from a variety of places.

Yes, before 4.2, we did a *lot* more work gathering flags, and the overhead you
see roughly corresponds with what I saw.


r~


      reply	other threads:[~2020-10-19 23:05 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-29 21:32 [RFC] Don't lookup full CPU state in the indirect branch fast path on AArch64 when running in user mode Owen Anderson
2020-10-12 20:52 ` Owen Anderson
2020-10-19 17:16   ` Owen Anderson
2020-10-19 18:22 ` Richard Henderson
2020-10-19 22:44   ` Owen Anderson
2020-10-19 22:58     ` Richard Henderson [this message]

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