#4029: ghci leaks memory when loading a file -------------------------------------+------------------------------------- Reporter: blarsen | Owner: Type: bug | Status: new Priority: normal | Milestone: ⊥ Component: GHCi | Version: Resolution: | Keywords: memory leak Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by jme): There is a new leak on the 8.0 branch. For example, running attachment:leak.script, which simply loads attachment:Leak.hs 20 times, results in a max residency of 115 MB: {{{ $ inplace/bin/ghc-stage2 --version The Glorious Glasgow Haskell Compilation System, version 8.0.0.20160206 $ inplace/bin/ghc-stage2 --interactive +RTS -t < leak.script > /dev/null <<ghc: 2104620200 bytes, 311 GCs, 26012178/114880456 avg/max bytes residency (11 samples), 236M in use, 0.002 INIT (0.002 elapsed), 1.869 MUT (1.882 elapsed), 1.425 GC ( 1.424 elapsed) :ghc>> }}} This is an obvious regression from 7.10.3, for which the max residency is 18.3 MB: {{{ $ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.10.3 $ ghc --interactive +RTS -t < leak.script > /dev/null <<ghc: 1757780832 bytes, 461 GCs, 11400611/18318760 avg/max bytes residency (16 samples), 48M in use, 0.002 INIT (0.002 elapsed), 1.362 MUT (1.367 elapsed), 1.150 GC (1. 149 elapsed) :ghc>> }}} There is a quick fix for the bulk of the leak (just make the `hsc_IC` field in `HscTypes.HscEnv` strict), but I'd like to track down what caused the regression before I submit a patch. In the meantime, anyone who needs a workaround (without recompiling) should periodically run a command which references the contents of the loaded module. For example, by querying the type of a constructor after each load, attachment:workaround.script is able to reduce the max residency to 29.1 MB: {{{ $ inplace/bin/ghc-stage2 --interactive +RTS -t < workaround.script > /dev/null <<ghc: 2106120848 bytes, 422 GCs, 16580354/29127088 avg/max bytes residency (14 samples), 80M in use, 0.002 INIT (0.002 elapsed), 1.862 MUT (1.875 elapsed), 1.363 GC (1. 363 elapsed) :ghc>> }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4029#comment:16> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler