[commit: ghc] master: Fix a scheduling bug in the threaded RTS (6d18141)

[Simon Marlow]

Repository : ssh://darcs.haskell.org//srv/darcs/ghc

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/6d18141d880d55958c3392f6a7ae621dc33ee5c1

>---------------------------------------------------------------

commit 6d18141d880d55958c3392f6a7ae621dc33ee5c1
Author: Simon Marlow <marlowsd at gmail.com>
Date:   Thu Dec 1 10:53:28 2011 +0000

    Fix a scheduling bug in the threaded RTS
    
    The parallel GC was using setContextSwitches() to stop all the other
    threads, which sets the context_switch flag on every Capability.  That
    had the side effect of causing every Capability to also switch
    threads, and since GCs can be much more frequent than context
    switches, this increased the context switch frequency.  When context
    switches are expensive (because the switch is between two bound
    threads or a bound and unbound thread), the difference is quite
    noticeable.
    
    The fix is to have a separate flag to indicate that a Capability
    should stop and return to the scheduler, but not switch threads.  I've
    called this the "interrupt" flag.

 includes/mkDerivedConstants.c |    1 +
 rts/Capability.c              |   10 ++++++++-
 rts/Capability.h              |   46 +++++++++++++++++++++++++++++++++--------
 rts/HeapStackCheck.cmm        |    3 +-
 rts/Messages.c                |    4 +-
 rts/Schedule.c                |   18 ++++++++++-----
 rts/Timer.c                   |    2 +-
 rts/sm/GC.c                   |    2 +-
 8 files changed, 65 insertions(+), 21 deletions(-)


Diff suppressed because of size. To see it, use:

    git show 6d18141d880d55958c3392f6a7ae621dc33ee5c1