Re: Proposal for a regular upstream performance testing

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Mon, Mar 28, 2022 at 08:18:43AM +0200, Lukáš Doktor wrote:
> Hello Stefan, folks,
> 
> I seem to have another hit, an improvement actually and it seems to be bisected all the way to you, Stefan. Let me use this as another example of how such process could look like and we can use this to hammer-out the details like via what means to submit the request, whom to notify and how to proceed further.
> 
> ---
> 
> Last week I noticed an improvement in TunedLibvirt/fio-rot-Aj-8i/0000:./write-4KiB/throughput/iops_sec.mean (<driver name="qemu" type="raw" io="native" cache="none"/>, fio, rotationary disk, raw file on host xfs partition, jobs=#cpus, iodepth=8, 4k writes) check and bisected it to:
> 
> commit fc8796465c6cd4091efe6a2f8b353f07324f49c7
> Author: Stefan Hajnoczi <stefanha@redhat.com>
> Date:   Wed Feb 23 15:57:03 2022 +0000
> 
>     aio-posix: fix spurious ->poll_ready() callbacks in main loop
> 
> Could you please confirm that it does make sense and that it is expected? (looks like it from the description).
> 
> Note that this commit was pin pointed using 2 out of 3 commits result, there were actually some little differences between commits fc8 and cc5. The fc8 and 202 results scored similarly to both, good and bad commits with 2 being closer to the bad one. Since cc5 they seem to stabilize further scoring slightly lower than the median fc8 result. Anyway I don't have enough data to declare anything. I can bisect it further if needed.

Yes, I can imagine that commit fc8796465c6c might improve non-IOThread
performance!

I don't know how to read the report:
- What is the difference between "Group stats" and "Failures"?
- Why are there 3 different means in "Group stats"?
- Why are there 3 "fc8" columns in "Failures"?

I don't feel confident searching git-log(1) output with 3-character
commit IDs. git itself uses 12 characters for short commit IDs with a
reasonably low chance of collisions.

Stefan

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