#13220: Performance regressions in testsuite from join points -------------------------------------+------------------------------------- Reporter: lukemaurer | Owner: lukemaurer Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Resolution: | Keywords: JoinPoints Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): I'm actually not sure that the effect on the whole is all that modest, unfortunately. [[https://perf.haskell.org/ghc/#revision/8d5cf8bf584fd4849917c29d82dcf46ee75dd035|Gipeda]] shows that the build time for GHC itself went up by 13%. While some increase is to be expected, this is quite significant. Are there any obvious knobs that could be adjusted to reduce the amount of work that the join point analysis/simplifier do under `-O1`? The full analysis is great for `-O2`, but I do fear that users will be up in arms if the GHC regression is representative of user code. Also, strangely enough, while the join points work eliminated all allocations from `fannkuch-redux`, the actual runtime of this test might have actually gone up by 8%. I say "might have" since runtime measurements are notoriously unstable, but it does look likely that this is a real regression: the test's runtime is quite long (4 seconds) and 8% is quite a large change. Even if this measurement were off by a factor of two we would want to understand it. Can you shed any light on this, Luke? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13220#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler