#10291: compiling huge HashSet hogs memory -------------------------------------+------------------------------------- Reporter: zudov | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Runtime (amd64) | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- Compiling a huge (~2.5k elements) set with GHC-7.10.1 or GHC-head and unordered-containers-0.2.5.1 or unordered-containers-head takes way too much memory. Here is a [https://github.com/zudov/html5-entity/blob/unordered- containers/src/Text/Html/Entity/Data/EntitySet.hs file] which I am trying to compile. I've also set up a [https://travis- ci.org/zudov/html5-entity/builds/58063328 travis build] which demonstrates the behaviour with different versions of GHC and unordered-containers. Further I would be referring to [https://travis- ci.org/zudov/html5-entity/jobs/58063332 this build-job] which uses GHC-7.10.1 and unordered-containers-0.2.5.1. * [https://travis-ci.org/zudov/html5-entity/jobs/58063332#L397 Compilation] with default optimization options takes around [https ://travis-ci.org/zudov/html5-entity/jobs/58063332#L408 12GB] of memory. * [https://travis-ci.org/zudov/html5-entity/jobs/58063332#L367 Compilation] with `-O0` takes around [https://travis- ci.org/zudov/html5-entity/jobs/58063332#L378 400MB]. * [https://travis-ci.org/zudov/html5-entity/jobs/58063332#L457 Compilation] with `-O2` takes around [https://travis- ci.org/zudov/html5-entity/jobs/58063332#L468 12GB] of memory. * [https://travis-ci.org/zudov/html5-entity/jobs/58063332#L487 Compilation] with `-O2 -fignore-interface-pragmas` takes around [https ://travis-ci.org/zudov/html5-entity/jobs/58063332#L498 500MB] of memory, which solves the problem. When the build uses GHC-7.8.4, neither of this hogging [https://travis- ci.org/zudov/html5-entity/jobs/58063330 occurs]. Another interesting observation is that [https://travis- ci.org/zudov/html5-entity/jobs/58063330#L339 compiling] [https://github.com/zudov/html5-entity/blob/unordered- containers/src/Text/Html/Entity/Data/EntityMap.hs HashMap] of the same size, doesn't cause memory hogging even with `-O2`. This attracted my attention as `HashSet` is implemented in terms of `HashMap`. I reported the issue to `unordered-containers` as well: [https://github.com/tibbe/unordered-containers/issues/100 link]. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10291 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler