Okay! So under UNIX, haskell threaded runtime uses pthreads, if I well understood.
To sum up, in order to achieve what I want, I have no other choice than compiling with '-threading' and importing as 'safe' the functions which can make a 'sleep'. Thanks! Ben Franksen wrote: > > Yves Parès wrote: >> I've also discovered something interesting: when I link with the >> 'threaded' runtime, but let the program use only one core (with '+RTS >> -N1'), the problem disappears. How comes? >> The whole thing remains a mystery, because I think what I'm trying to do >> is quite common... >> >> >> Yves Parès wrote: >>> >>> There is a minimal code which produces this issue: >>> http://old.nabble.com/file/p27613138/func.c func.c >>> http://old.nabble.com/file/p27613138/main.hs main.hs >>> >>> >>> Yves Parès wrote: >>>> >>>> Well I tried both 'unsafe' and 'safe', and actually I saw no >>>> difference... >>>> Even with 'safe', I see a huge difference between calling a C function >>>> which sleeps and another which doesn't. When there is a sleep, the >>>> other >>>> thread is really slower (it just prints numbers, and I look at which >>>> pace they're displayed). > > This is to be expected. From the docs > (http://www.haskell.org/ghc/docs/latest/html/libraries/base-4.2.0.0/Control-Concurrent.html#10): > > "The downside of having lightweight threads is that only one can run at a > time, so if one thread blocks in a foreign call, for example, the other > threads cannot continue. The GHC runtime works around this by making use > of > full OS threads where necessary. When the program is built with > the -threaded option (to link against the multithreaded version of the > runtime), a thread making a safe foreign call will not block the other > threads in the system; another OS thread will take over running Haskell > threads until the original call returns. The runtime maintains a pool of > these worker threads so that multiple Haskell threads can be involved in > external calls simultaneously." > > IIRC, with -threaded, the RTS spawns a separate OS thread for 'safe' > foreign > calls _in addition_ to the OS threads used for Haskell code (the number of > which you give with the +RTS -N<n> option). > > Cheers > Ben > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > > ----- Yves Parès Live long and prosper -- View this message in context: http://old.nabble.com/Threading-and-FFI-tp27611528p27631980.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe