#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): Updated performance graph: https://ghc.haskell.org/trac/ghc/attachment/ticket/7258/ghc-large-record- types-optimized.png (this one uses -O, not -O2) Key observation: read, read-appl and show "explode" while all the other examples, including getline-appl and getline, behave properly. A sample profile like the one for 400-field read, shows that the bottleneck is no longer ASM output or register allocation anymore once -O is involved: {{{ Thu Oct 26 01:25 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 examples/t-400-read.hs total time = 128.62 secs (128624 ticks @ 1000 us, 1 processor) total alloc = 37,659,351,320 bytes (excludes profiling overheads) COST CENTRE MODULE SRC %time %alloc sink CmmPipeline compiler/cmm/CmmPipeline.hs:(104,13)-(105,59) 77.8 23.6 SimplTopBinds SimplCore compiler/simplCore/SimplCore.hs:761:39-74 9.6 30.0 FloatOutwards SimplCore compiler/simplCore/SimplCore.hs:471:40-66 3.0 10.4 RegAlloc-linear AsmCodeGen compiler/nativeGen/AsmCodeGen.hs:(658,27)-(660,55) 1.6 5.0 OccAnal SimplCore compiler/simplCore/SimplCore.hs:(739,22)-(740,67) 1.1 4.2 pprNativeCode AsmCodeGen compiler/nativeGen/AsmCodeGen.hs:(529,37)-(530,65) 1.0 4.7 NewStranal SimplCore compiler/simplCore/SimplCore.hs:480:40-63 0.9 4.2 CoreTidy HscMain compiler/main/HscMain.hs:1253:27-67 0.7 2.9 StgCmm HscMain compiler/main/HscMain.hs:(1426,13)-(1427,62) 0.6 1.9 regLiveness AsmCodeGen compiler/nativeGen/AsmCodeGen.hs:(591,17)-(593,52) 0.5 1.4 genMachCode AsmCodeGen compiler/nativeGen/AsmCodeGen.hs:(580,17)-(582,62) 0.4 1.3 NativeCodeGen CodeOutput compiler/main/CodeOutput.hs:171:18-78 0.4 1.6 CommonSubExpr SimplCore compiler/simplCore/SimplCore.hs:462:40-56 0.2 1.1 deSugar HscMain compiler/main/HscMain.hs:511:7-44 0.2 1.1 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/7258#comment:56 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler