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From: Peter Maydell <peter.maydell@linaro.org>
Date: Sat, 11 Mar 2017 16:02:47 +0100
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Subject: Re: [Qemu-devel] Benchmarking linux-user performance
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To: "Emilio G. Cota" <cota@braap.org>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>, Richard Henderson <rth@twiddle.net>, Laurent Vivier <laurent@vivier.eu>, Paolo Bonzini <pbonzini@redhat.com>, =?UTF-8?Q?Alex_Benn=EF=BF=BDe?= <alex.bennee@linaro.org>, qemu-devel <qemu-devel@nongnu.org>

On 11 March 2017 at 03:25, Emilio G. Cota <cota@braap.org> wrote:
> On Fri, Mar 10, 2017 at 12:48:31 +0100, Peter Maydell wrote:
>> Given the scale on the LHS is from 1.74 to 1.88 my guess is that the
>> variation is in large part noise and the major thing is "our fp
>> performance is bounded by softfloat, which doesn't change and is
>> always very slow".
>
> It isn't "measurement noise" -- if you look at the PNGs the measurements
> are very stable (all points have error bars): http://imgur.com/a/nF7Ls
>
> It's true that performance here varies very little. This is just the
> result of Amdahl's law, as you point out. (upon re-reading your message,
> I see that perhaps what you meant by "noise" is exactly this.)

Yes, sorry, I wasn't really using the right terminology there.
I just meant that the release-to-release variation is not as
significant as it appears from the graph, because the LHS axis
scale is covering such a small range.

thanks
-- PMM