#15418: Performance drop 60 times on non-profiling binary -------------------------------------+------------------------------------- Reporter: hth313 | Owner: (none) Type: bug | Status: infoneeded Priority: high | Milestone: 8.8.1 Component: Runtime System | Version: 8.4.3 Resolution: | Keywords: Operating System: MacOS X | Architecture: x86_64 Type of failure: Runtime | (amd64) performance bug | Test Case: Blocked By: | Blocking: Related Tickets: #14414, #9599 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by osa1): OK, so profiling build is faster than any of these .. Becuase we can't see the source you'll have to debug this yourself. Here's what I'd do next: - Add `-ddump-simpl -ddump-to-file -dsuppress-uniques` to `ghc-options` in your .cabal, and build without profiling. Copy generated .dump-simpl files to another directory, and build again this time with profiling (make sure to use same optimisation settings in both!), copy the .dump-simpl files again to another directory. Do directory diff (perhaps using kdiff3) and see the differences. You should see lots of minor changes (like the extra `scc` expression in the profiled version) and those should not matter, focus on larger changes. Looking at results in comment:13, you should see some code in non-profiled version that allocates more. One example where this happens is when GHC unboxes strict arguments/fields but not in the whole program so you still need the boxed version of the value. In that case at some point you re-box the value, causing more allocation. There are other reasons too, hard to list all.. - Looking at the numbers in comment:13, it looks like profiling version has less max residency. Perhaps in non-profiled version some closures are floated to the top-level, causing increased residency. Keep this in mind when comparing Core outputs. Failing all that, try to extract some minimal reproducer from your code base and share it :-) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15418#comment:19 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler