#10613: Mechanism for checking that we only enter single-entry thunks once -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Other | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by nomeata): I have made initial, still hackish, progress. After a few iterations I can now run all of nofib with my counting indirections and it does not segfault any more (phew). Here is a report from `integrate`, note the new columns `#Alloc`, `Single` and `Multpile`. {{{ Entries Alloc Alloc'd #Alloc Single Multiple Non- void Arguments STG Name -------------------------------------------------------------------------------- 50000 800000 0 0 0 0 1 D main@main:Main.main6{v r7sX} 0 0 8000000 500000 0 0 0 sat_s7u6{v} (main@main:Main) (thk) in r7sQ 0 0 8000000 500000 0 0 0 sat_s7u3{v} (main@main:Main) (thk) in r7sQ 0 0 8000000 500000 0 0 0 sat_s7tZ{v} (main@main:Main) (thk) in r7sQ 0 0 8000000 500000 0 0 0 sat_s7tU{v} (main@main:Main) (thk) in r7sQ 0 0 8000000 500000 0 0 0 sat_s7tP{v} (main@main:Main) (thk) in r7sQ 0 0 8000000 500000 0 0 0 sat_s7tK{v} (main@main:Main) (thk) in r7sQ 0 0 8000000 500000 0 0 0 sat_s7tF{v} (main@main:Main) (thk) in r7sQ 0 0 8000000 500000 0 0 0 sat_s7tA{v} (main@main:Main) (thk) in r7sQ 4050000 0 7200000 450000 0 450000 1 D sat_s7uz{v} (main@main:Main) in s7uB 0 0 8000000 500000 0 0 0 sat_s7tu{v} (main@main:Main) (thk) in r7sQ 500000 72000000 0 0 0 0 3 dd> main@main:Main.$wintegrate1D{v r7sQ} 450000 32400000 800000 50000 0 50000 1 D sat_s7uB{v} (main@main:Main) in r7t3 50000 800000 0 0 0 0 1 D main@main:Main.main10{v r7t2} 50000 3600000 0 0 0 0 2 DD main@main:Main.main11{v r7t3} 50000 0 0 0 0 0 4 LLid main@main:Main.$wgo{v r7t4} 2 0 24 1 1 0 0 sat_s7vH{v} (main@main:Main) (thk) in r7sR 1 64 0 0 0 0 0 main@main:Main.main1{v r7sR} 1 0 0 0 0 0 0 main@main:Main.main15{v r7t9} 1 0 0 0 0 0 0 main@main::Main.main{v 01D} }}} It is still buggy (or not fully understood), e.g.: * I thought I only enabled it for thunks, but it also seems to be present for two functions, and only there count multiple entries... Weird. * Also, these 500000-times allocated thunks are not really unused, are they?. * Two total entries for a thunk (`sat_s7vH`) that has been allocated once and called once? Maybe there was a heap check inbetween? But still: You can tell that `sat_s7uB` has been allocated 50000 and each instance is called 9 times – this matches the 9-element-list in the code. The implementation uses a new closure type that carries a pointer to a ticky counter struct, and its own little counter: {{{ typedef struct { StgHeader header; StgClosure *indirectee; const void *ent_counter; // A StgEntCounter StgWord entries; } StgIndCounting; }}} Upon entry, this increments the private counter, and if it does so the first time, increases `Single`, and on the second time decreases `Single` and increases `Multiple`. Otherwise, it passes `R1` onto the indirectee, preserving the tag. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10613#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler