Yeah, it's not like a big deal or anything. Here's all the places which grep told me use chains of || (or long switch statements which can't be turned into tables) to compare these values:
ghc/rts//win32/AsyncIO.c:280 ghc/rts//Threads.c:286 ghc/rts//Threads.c:257 ghc/rts//sm/Scav.c:73 ghc/rts//sm/Sanity.c:521 ghc/rts//sm/Compact.c:436 ghc/rts//Schedule.c:2617 ghc/rts//Schedule.c:2605 ghc/rts//Schedule.c:946 ghc/rts//RaiseAsync.h:54 ghc/rts//RaiseAsync.c:416 I didn't include all the ones in the profiler because they probably don't get hot. Kyle On Sun, Jul 20, 2014 at 4:43 AM, Jost Berthold < berth...@mathematik.uni-marburg.de> wrote: > Message: 2 >> Date: Sat, 19 Jul 2014 15:00:17 +1000 >> From: Kyle Van Berendonck <kvanberendo...@gmail.com> >> To: "ghc-devs@haskell.org" <ghc-devs@haskell.org> >> Subject: Thread status constants >> Message-ID: >> <CAFSvR6A3maSWngY=GJdATvGPjTAyuPokXZ5=rLtLT=EbYd >> s...@mail.gmail.com> >> Content-Type: text/plain; charset="utf-8" >> >> Hi, >> >> I found these: >> https://github.com/ghc/ghc/blob/5f3c5384df59717ca8013c5df8d1f6 >> 5692867825/includes/rts/Constants.h#L194 >> >> They go only 0-14, so there's some long chains of branches and stuff in >> hot >> paths that could be cleaned up into single &-masked branches by changing >> these into a set of flags. >> >> And then I saw these: >> https://github.com/ghc/ghc/blob/master/libraries/base/ >> GHC/Conc/Sync.lhs#L483 >> >> Where does 16 and 17 come from -- I couldn't find them in the header files >> anywhere? >> >> Kyle >> > > Hi Kyle, > > I had a look at these constants just recently. > > About 16 and 17, see here: > https://github.com/ghc/ghc/blob/master/rts/PrimOps.cmm#L853 > > About the others:The block reasons received two updates just recently. > Turns out that the eventlog (GHC's post-mortem tracing for threadscope et > al.) expects these states to have particular values (those in > includes/rts/Constants.h, consider them a fixed ABI for the time being). > See here for the story: > https://ghc.haskell.org/trac/ghc/ticket/9003 > > NB: Darn... base still uses GHC-7.8.2 constants. Thanks for the pointer! > > About your proposal to use bit masks: > > Did you find some of those hot paths? > I believe (believe, unchecked...) that there are not too many places where > a complete switch over all possible reasons is done (apart from debug > output maybe); the typical use is rather to compare to one single constant > than to all. So the performance might not increase too much from > optimisations. Again, just a hunch, not verified. > > If the RTS contains code specialised to the current constants, these > places need to be kept symbolic, to avoid future breakage when new states > are added. > > A fix which removes the tight implicit dependency of ghc-events from the > constants in includes/rts/Constants.h is pending, btw. > > / Jost > >
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