Ben, David

I’m still baffled by how to reliably get GHC perf metrics on my local machine.

The wiki page https://gitlab.haskell.org/ghc/ghc/wikis/building/running-tests/performance-tests helps, but not enough!

• There are two things going on:

1. CI perf measurements
2. Local machine perf measurements

I think that they are somehow handled differently (why?) but they are all muddled up on the wiki page.

• My goal is this:

• Start with a master commit, say from Dec 2019.
• Implement some change, on a branch.
• sh validate –legacy (or something else if you like)
• Look at perf regressions.
• I believe I have first to utter the incantation

$ git fetch https://gitlab.haskell.org/ghc/ghc-performance-notes.git refs/notes/perf:refs/notes/ci/perf

• But then:
• How do I ensure that the baseline perf numbers I get relate to the master commit I started from, back in Dec 2019?  I don’t want numbers from Jan 2020.
• If I rebase my branch on top of HEAD, say, how do I update the perf baseline numbers to be for HEAD?
• Generally, how can I tell the commit to which the baseline numbers relate?
• Also, in my tree I have a series of incremental changes; I want to see if any of them have perf regressions.    How do I do that?

Thanks

Simon