Skip to content
Snippets Groups Projects

Profiling binary consumes CPU even when idle on Linux.

    • Closed Issue created by robinp @trac-robinp

    The program is

    import Control.Concurrent
import Control.Monad (forever)
main :: IO ()
main = forever $ threadDelay 1000000 >> return ()

    Compiled with 32bit GHC 7.6.3 or 7.8.2 on Debian (inside a VM), GHC 7.4.1 on Ubuntu (not VM). The non-profiling binary doesn't consume CPU, the profiling does ~10% (of a 2Ghz machine). Running with +RTS -I0, so this is not the idle gc.

    When strace-ing, the profiling one seems to receive a constant flow of SIGVTALRM, while the normal receives one burst each second.

    I see I can switch off "master tick interval" with -V0, and then CPU is not used, but the consequences of this are not very well documented (apart from context switching becoming deterministic).

    Interestingly, if I compile using profiling on Windows (latest haskell-platform, 64-bit), it doesn't use more CPU than the non-profiling.

    So, the question is, why does this happen on Linux, and if it can be avoided somehow.

    Edited by Ben Gamari
    To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information

    Child items ...

    • Activity

    Please register or sign in to reply