#7258: Compiling DynFlags is jolly slow -------------------------------------+------------------------------------- Reporter: simonpj | Owner: simonpj Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.1 Resolution: | Keywords: deriving-perf 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 tdammers): Stg2Stg turns out to b a dead end. The performance loss I observed there is entirely due to formatting and dumping about 1.3 GiB worth of STG when compiling with -ddump-stg; when compiling without -ddump-stg, `Stg2Stg` doesn't show up in the profile at all (0.0 on everything). Re-running the profiling script without dumps shows different culprits: `tryToInline`, and `simpl_bind`. E.g. 400-field `read`: {{{ Fri Nov 3 08:43 2017 Time and Allocation Profiling Report (Final) ghc-stage2 +RTS -p -h -RTS -B/home/tobias/well- typed/devel/ghc/inplace/lib -B/home/tobias/well- typed/devel/ghc/inplace/lib -O -fforce-recomp -c generated/t-400-read.hs total time = 59.05 secs (59049 ticks @ 1000 us, 1 processor) total alloc = 75,366,446,544 bytes (excludes profiling overheads) COST CENTRE MODULE SRC %time %alloc simpl_bind Simplify compiler/simplCore/Simplify.hs:141:83-101 29.4 22.0 tryToInline CmmSink compiler/cmm/CmmSink.hs:410:3-41 24.4 32.4 RegAlloc-linear AsmCodeGen compiler/nativeGen/AsmCodeGen.hs:(658,27)-(660,55) 10.6 14.1 FloatOutwards SimplCore compiler/simplCore/SimplCore.hs:471:40-66 8.8 6.9 pprNativeCode AsmCodeGen compiler/nativeGen/AsmCodeGen.hs:(529,37)-(530,65) 4.0 4.7 OccAnal SimplCore compiler/simplCore/SimplCore.hs:(739,22)-(740,67) 2.3 2.2 StgCmm HscMain compiler/main/HscMain.hs:(1426,13)-(1427,62) 2.1 1.8 regLiveness AsmCodeGen compiler/nativeGen/AsmCodeGen.hs:(591,17)-(593,52) 1.9 1.3 NativeCodeGen CodeOutput compiler/main/CodeOutput.hs:171:18-78 1.5 1.6 genMachCode AsmCodeGen compiler/nativeGen/AsmCodeGen.hs:(580,17)-(582,62) 1.4 1.3 CoreTidy HscMain compiler/main/HscMain.hs:1253:27-67 1.3 1.4 dmdAnal'-Case-single_prod_ctor DmdAnal compiler/stranal/DmdAnal.hs:(251,5)-(276,68) 1.3 1.5 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/7258#comment:82 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler