Re: [REPORT] [GSoC - TCG Continuous Benchmarking] [#3] QEMU 5.0 and 5.1-pre-soft-freeze Dissect Comparison

[Alex Bennée]

Ahmed Karaman <ahmedkhaledkaraman@gmail.com> writes:

> Hi,
>
> The third report of the TCG Continuous Benchmarking series utilizes
> the tools presented in the previous report for comparing the
> performance of 17 different targets across two versions of QEMU. The
> two versions addressed are 5.0 and 5.1-pre-soft-freeze (current state
> of QEMU).
>
> After summarizing the results, the report utilizes the KCachegrind
> tool and dives into the analysis of why all three PowerPC targets
> (ppc, ppc64, ppc64le) had a performance degradation between the two
> QEMU versions.

It's an interesting degradation especially as you would think that a
change in the softfloat implementation should hit everyone in the same
way.

We actually have a tool for benchmarking the softfloat implementation
itself called fp-bench. You can find it in tests/fp. I would be curious
to see if you saw a drop in performance in the following:

  ./fp-bench -p double -o cmp

>
> Report link:
> https://ahmedkrmn.github.io/TCG-Continuous-Benchmarking/QEMU-5.0-and-5.1-pre-soft-freeze-Dissect-Comparison/

If you identify a drop in performance due to a commit linking to it from
the report wouldn't be a bad idea so those that want to quickly
replicate the test can do before/after runs.

>
> Previous reports:
> Report 1 - Measuring Basic Performance Metrics of QEMU:
> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg06692.html
> Report 2 - Dissecting QEMU Into Three Main Parts:
> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg09441.html
>
> Best regards,
> Ahmed Karaman


-- 
Alex Bennée