#10370: Compile time regression in OpenGLRaw -------------------------------------+------------------------------------- Reporter: michalt | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by liyang): * cc: ghc.haskell.org@… (added) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10370#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10370: Compile time regression in OpenGLRaw -------------------------------------+------------------------------------- Reporter: michalt | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by simonpj): Sven Panne [https://mail.haskell.org/pipermail/glasgow-haskell- users/2015-May/025857.html says]: To alleviate the pain a bit, I've uploaded a new version of OpenGLRaw (2.5.0.0) to Hackage, containing 2 improvements: * `foreign import "dynamic"`s with the same signature are re-used, cutting down their number from 3062 to 864. * Those `foreign import "dynamic"`s live in a separate module now. Travis CI seems to be happy with these changes (the VMs there don't have much memory, either), although Haddock still seems to eat memory like hell. But that's a different story... -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10370#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10370: Compile time regression in OpenGLRaw -------------------------------------+------------------------------------- Reporter: michalt | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Description changed by simonpj: Old description:

As reported by Paolo Veronelli:

Hello, I'm using ghc 7.10.1 to compile OpenGLRaw which is now impossible with -O1 and -O2 due to "ghc : out of memory error" on a 4GB linux host. The file making memory explode is Graphics.Rendering.OpenGL.Raw.Functions. With -O0 it uses 600 MB.

The file is really huge, but I could compile it with prior versions of ghc.

I've had a look and indeed the file takes way more memory to compile with HEAD. Looking at the heap profiles, it seems that the problem is in GHC itself (space leak somewhere?). I'll attach the heap profiles (from compiling the single module itself, i.e., `touch`ing the file and running prof GHC on it).

New description: As reported by Paolo Veronelli: Hello, I'm using ghc 7.10.1 to compile OpenGLRaw which is now impossible with -O1 and -O2 due to "ghc : out of memory error" on a 4GB linux host. The file making memory explode is Graphics.Rendering.OpenGL.Raw.Functions. With -O0 it uses 600 MB. The file is really huge, but I could compile it with prior versions of ghc. I've had a look and indeed the file takes way more memory to compile with HEAD. Looking at the heap profiles, it seems that the problem is in GHC itself (space leak somewhere?). I'll attach the heap profiles (from compiling the single module itself, i.e., `touch`ing the file and running prof GHC on it). Paolo also says: ere is another file , which is small, which cannot be compiled within 4GB memory. https://raw.githubusercontent.com/benl23x5/gloss/master/gloss- examples/raster/Fluid/src-repa/Stage/Linear.hs -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10370#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10370: Compile time regression in OpenGLRaw -------------------------------------+------------------------------------- Reporter: michalt | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by michalt): I'm a bit stuck. I've had a look at that commit, but I don't really understand simplifier well enough to find the reason of the blow-up. Any ideas are welcome! :-) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10370#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10370: Compile time regression in OpenGLRaw -------------------------------------+------------------------------------- Reporter: michalt | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by michalt): tl;dr: No difference If anyone wants to try to reproduce: checkout b0379819e46796047c1574a6abccf186afd27afa and then revert b8392ae76a6d39c57be94b5ba041c450ab479e2b -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10370#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10370: Compile time regression in OpenGLRaw -------------------------------------+------------------------------------- Reporter: michalt | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by Simon Peyton Jones ): In [changeset:"45d9a15c4b85a2ed89579106bdafd84accf2cb39/ghc"]: {{{ #!CommitTicketReference repository="ghc" revision="45d9a15c4b85a2ed89579106bdafd84accf2cb39" Fix a huge space leak in the mighty Simplifier This long-standing, terrible, adn somewhat subtle bug was exposed by Trac #10370, thanks to Reid Barton's brilliant test case (comment:3). The effect is large on the Trac #10370 test. Here is what the profile report says: Before: total time = 24.35 secs (24353 ticks @ 1000 us, 1 processor) total alloc = 11,864,360,816 bytes (excludes profiling overheads) After: total time = 21.16 secs (21160 ticks @ 1000 us, 1 processor) total alloc = 7,947,141,136 bytes (excludes profiling overheads) The /combined/ effect of the tidyOccName fix, plus this one, is dramtic for Trac #10370. Here is what +RTS -s says: Before: 15,490,210,952 bytes allocated in the heap 1,783,919,456 bytes maximum residency (20 sample(s)) MUT time 30.117s ( 31.383s elapsed) GC time 90.103s ( 90.107s elapsed) Total time 120.843s (122.065s elapsed) After: 7,928,671,936 bytes allocated in the heap 52,914,832 bytes maximum residency (25 sample(s)) MUT time 13.912s ( 15.110s elapsed) GC time 6.809s ( 6.808s elapsed) Total time 20.789s ( 21.954s elapsed) - Heap allocation halved - Residency cut by a factor of more than 30. - ELapsed time cut by a factor of 6 Not bad! The details ~~~~~~~~~~~ The culprit was SimplEnv.mkCoreSubst, which used mapVarEnv to do some impedence-matching from the substitituion used by the simplifier to the one used by CoreSubst. But the impedence-mactching was recursive! mk_subst tv_env cv_env id_env = CoreSubst.mkSubst in_scope tv_env cv_env (mapVarEnv fiddle id_env) fiddle (DoneEx e) = e fiddle (DoneId v) = Var v fiddle (ContEx tv cv id e) = CoreSubst.substExpr (mk_subst tv cv id) e Inside fiddle, in the ContEx case, we may do another whole level of fiddle. And so on. Moreover, UniqFM (which is built on Data.IntMap) is strict, so the fiddling is done eagerly. I didn't wok through all the details but the result is a gargatuan blow-up of entirely unnecessary work. Laziness would make this go away, I think, but I don't want to mess with IntMap. And in any case, the impedence matching is a royal pain. In the end I simply ceased trying to use CoreSubst.substExpr in the simplifier, and instead just use simplExpr. That does mean bit of duplication; e.g. new code for simplRules. But it's not a big deal and it's far more direct and easy to reason about. A bit of knock-on refactoring: * Data type ArgSummary moves to CoreUnfold. * interestingArg moves from CoreUnfold to SimplUtils, and gets a SimplEnv argument which can be used when we encounter a variable. * simplLamBndrs, addBndrRules move from SimplEnv to Simplify (because they now calls simplUnfolding, simplRules resp) * SimplUtils.substExpr, substUnfolding, mkCoreSubst die completely * In Simplify some several functions that were previously pure substitution-based functions are now monadic: - addBndrRules, simplRule - addCoerce, add_coerce in simplCast * In case 2c of Simplify.rebuildCase, there was a pretty disgusting expression-substitution taking place for 'rhs'; and we really don't want to make that monadic becuase 'rhs' can be big. Solution: reduce the arity of the rules for seq. See Note [User-defined RULES for seq] in MkId. }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10370#comment:12 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10370: Compile time regression in OpenGLRaw -------------------------------------+------------------------------------- Reporter: michalt | Owner: Type: bug | Status: merge Priority: normal | Milestone: 7.10.2 Component: Compiler | Version: 7.10.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by thoughtpolice): * status: new => merge * milestone: => 7.10.2 Comment: Yeah, so we want something smaller, we don't need the 20 second variant. We can probably just cut Reid's test case in half or even a third and check that in, double checking the behavior is still fixed (which is obviously pretty easy). I'll get on it shortly. I'm also moving this to 7.10.2 - the `tidyOccName` fix already applies cleanly in my tree. The evil simplifier bug applies modulo a small change in `SimplCore` - so this is an excellent bugfix to go in! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10370#comment:14 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#10370: Compile time regression in OpenGLRaw -------------------------------------+------------------------------------- Reporter: michalt | Owner: Type: bug | Status: closed Priority: normal | Milestone: 7.10.2 Component: Compiler | Version: 7.10.1 Resolution: fixed | Keywords: 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 bgamari): I'ved opened Phab:D1352 to add a performance test for this issue. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10370#comment:16 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler