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From: Owen Anderson <oanderso@google.com>
To: Richard Henderson <richard.henderson@linaro.org>
Cc: qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>
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 15:44:12 -0700	[thread overview]
Message-ID: <CAKs3XfKMpTaAO6vj-V--zp_zY_Jm9HKkgkpCbCCKCQHSDT8y3g@mail.gmail.com> (raw)
In-Reply-To: <7c416109-6431-076e-2284-0f8406931ab9@linaro.org>

On Mon, Oct 19, 2020 at 11:22 AM Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> (1) What qemu version are you looking at and,
> (2) Do you have --enable-tcg-debug enabled?

My use case is a large automated testing environment for large C++
binaries with heavy use of virtual dispatch.  The binaries are
generally not built at high optimization levels (-O0 or -O1), so it's
not very surprising to me that indirect branches are more dominant in
this as a workload

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.

--Owen


  reply	other threads:[~2020-10-19 22:45 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 [this message]
2020-10-19 22:58     ` Richard Henderson

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