Hi devs! I've recently started working on a few compiler perf related tickets, and wondered how to verify that a change actually has a positive impact on compiler performance. I first looked at the wiki for information on this, but didn't find much: https://gitlab.haskell.org/ghc/ghc/-/wikis/performance/compiler doesn't contain any information on how to measure compiler performance The best tip I found was the recommendation in https://gitlab.haskell.org/ghc/ghc/-/wikis/building/running-no-fib to compile nofib/spectral/simple/Main.hs. With -O0 and -O that takes respectively about 1.5s and 5s for me, so the effort is manageable. I've also done full nofib runs, but they take a very long time. A problem in this context is that reliable performance measurements require a quiet machine. Closing my browser, and turning off other programs is – in my perception – rather inconvenient, particularly when I have to do it for a prolonged time. Ideally I wouldn't have to perform these measurements on my local machine at all! Do you usually use a separate machine for this? _Very_ convenient would be some kind of bot whom I could tell e.g. @perf-bot compiler perf …or more concretely @perf-bot compile nofib/spectral/simple/Main.hs …or just @nofib-bot run … or something like that. I've noticed that CI now includes a perf-nofib job. But since it appears to run on a different machine each time, I'm not sure whether it's actually useful for comparing performance. Could it be made more useful by running it consistently on the same dedicated machine? Another question regarding performing compiler perf measurements locally is which build flavour to use: So far I have used the "perf" flavour. A problem here is that a full build seems to take close to an hour. A rebuild with --freeze1 takes ~15 minutes on my machine. Is this the right flavour to use? BTW what's the purpose of the profiled GHC modules built with this flavour which just seem to additionally prolong compile time? I don't see a ghc-prof binary or similar in _build/stage1/bin. Also, what's the status of gipeda? The most recent commit at https://perf.haskell.org/ghc/ is from "about a year ago"? Sorry for this load of questions and complaints! I do believe though that if work on compiler performance was a bit better documented and more convenient, we might see even more progress on that front. :) Cheers, Simon