Perf notes

[David Eichmann]

Hi Simon,

skip to the list at the bottom for TL;DR

Every time I get an email about perf notes my heart sinks a little. 
Hopefully there isn't a big issues here.

First of all, what commit is your branch based on? Have you rebased on a 
recent master?

The output you posted says "...increased from x86_64-linux-deb9 baseline 
@ HEAD~28". So this means it is using metrics from CI as a baseline 
(that's the "x86_64-linux-deb9" part), but the baseline is from 28 
commits ago (that's the "HEAD~28" part). The baseline seems a bit old. 
Also looking at gitlab CI, there are a lot of recent commits on master 
without completed CI runs.  So this might be a matter of waiting for CI 
to finish, then fetching the CI metrics again. Any way this may help:


TL;DR


1. Rebase of the latest master

2. Wait for CI to finish on a more recent commit (see 
https://gitlab.haskell.org/ghc/ghc/-/commits/master)

3.git fetch https://gitlab.haskell.org/ghc/ghc-performance-notes.git 
<https://gitlab.haskell.org/ghc/ghc-performance-notes.git>

refs/notes/perf:refs/notes/ci/perf

4. Re run the tests


Alternatively you can generate local metrics


1. Checkout a recent commit to use as the baseline (make sure the 
working tree is clean)

2. Run the relevant perf tests

3. Checkout your branches HEAD commit again

4. Run the relevant tests again.


If that doesn't do it, I can have a closer look.


David E


On 6/26/20 11:29 AM, Simon Peyton Jones via ghc-devs wrote:
>
> Despite a recent
>
> git fetch https://gitlab.haskell.org/ghc/ghc-performance-notes.git 
> <https://gitlab.haskell.org/ghc/ghc-performance-notes.git>
>
> refs/notes/perf:refs/notes/ci/perf
>
> I’m getting lots of perf regressions in HEAD. For example
>
> =====> T9203(normal) 1 of 1 [0, 0, 0]
>
> ]0;T9203(normal) 1 of 1 [0, 0, 0]cd "T9203.run" && 
> "/home/simonpj/code/HEAD-3/inplace/bin/ghc-stage2" -o T9203 T9203.hs 
> -dcore-lint -dstg-lint -dcmm-lint -no-user-package-db -rtsopts 
> -fno-warn-missed-specialisations -fshow-warning-groups 
> -fdiagnostics-color=never -fno-diagnostics-show-caret -Werror=compat 
> -dno-debug-output  -O2<
>
> cd "T9203.run" && ./T9203  +RTS -V0 -tT9203.stats --machine-readable 
> -RTS <
>
> runtime/bytes allocated increased from x86_64-linux-deb9 baseline @ 
> HEAD~28:
>
>     Expected    T9203 (normal) runtime/bytes allocated: 56046952.0 +/-5%
>
>     Lower bound T9203 (normal) runtime/bytes allocated:   53244604
>
>     Upper bound T9203 (normal) runtime/bytes allocated:   58849300
>
>     Actual      T9203 (normal) runtime/bytes allocated:  108464536
>
>     Deviation   T9203 (normal) runtime/bytes allocated:       93.5 %
>
> *** unexpected stat test failure for T9203(normal)
>
> Performance Metrics (test environment: local):
>
> T9203(normal) runtime/bytes allocated                     108464536.000
>
>                       (baseline @ HEAD~28)                         
> 56046952.000  [increased, 93.5%]
>
> What am I doing wrong?
>
> Simon
>
>
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-- 
David Eichmann, Haskell Consultant
Well-Typed LLP, http://www.well-typed.com

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