ghc/rts/Timer.c

   1 /* -----------------------------------------------------------------------------
   2  *
   3  * (c) The GHC Team, 1995-2003
   4  *
   5  * Interval timer service for profiling and pre-emptive scheduling.
   6  *
   7  * ---------------------------------------------------------------------------*/
   8
   9 /*
  10  * The interval timer is used for profiling and for context switching in the
  11  * threaded build.
  12  *
  13  * This file defines the platform-independent view of interval timing, relying
  14  * on platform-specific services to install and run the timers.
  15  *
  16  */
  17 #include "Rts.h"
  18 #include "RtsFlags.h"
  19 #include "Proftimer.h"
  20 #include "Schedule.h"
  21 #include "Timer.h"
  22 #include "Capability.h"
  23
  24 #if !defined(mingw32_HOST_OS)
  25 #include "Itimer.h"
  26 #else
  27 #include "win32/Ticker.h"
  28 #endif
  29
  30 /* ticks left before next pre-emptive context switch */
  31 static int ticks_to_ctxt_switch = 0;
  32
  33 #if defined(RTS_SUPPORTS_THREADS)
  34 /* idle ticks left before we perform a GC */
  35 static int ticks_to_gc = 0;
  36 #endif
  37
  38 /*
  39  * Function: handle_tick()
  40  *
  41  * At each occurrence of a tick, the OS timer will invoke
  42  * handle_tick().
  43  */
  44 static
  45 void
  46 handle_tick(int unused STG_UNUSED)
  47 {
  48 #ifdef PROFILING
  49   handleProfTick();
  50 #endif
  51   if (RtsFlags.ConcFlags.ctxtSwitchTicks > 0) {
  52       ticks_to_ctxt_switch--;
  53       if (ticks_to_ctxt_switch <= 0) {
  54           ticks_to_ctxt_switch = RtsFlags.ConcFlags.ctxtSwitchTicks;
  55           context_switch = 1;   /* schedule a context switch */
  56
  57 #if defined(RTS_SUPPORTS_THREADS)
  58           /*
  59            * If we've been inactive for idleGCDelayTicks (set by +RTS
  60            * -I), tell the scheduler to wake up and do a GC, to check
  61            * for threads that are deadlocked.
  62            */
  63           switch (recent_activity) {
  64           case ACTIVITY_YES:
  65               recent_activity = ACTIVITY_MAYBE_NO;
  66               ticks_to_gc = RtsFlags.GcFlags.idleGCDelayTicks;
  67               break;
  68           case ACTIVITY_MAYBE_NO:
  69               if (ticks_to_gc == 0) break; /* 0 ==> no idle GC */
  70               ticks_to_gc--;
  71               if (ticks_to_gc == 0) {
  72                   ticks_to_gc = RtsFlags.GcFlags.idleGCDelayTicks;
  73                   recent_activity = ACTIVITY_INACTIVE;
  74                   blackholes_need_checking = rtsTrue;
  75                   /* hack: re-use the blackholes_need_checking flag */
  76                   threadRunnable();
  77                   /* ToDo: this threadRunnable only works if there's
  78                    * another thread (not this one) waiting to be woken up
  79                    */
  80               }
  81               break;
  82           default:
  83               break;
  84           }
  85 #endif
  86       }
  87   }
  88 }
  89
  90 int
  91 startTimer(nat ms)
  92 {
  93 #ifdef PROFILING
  94   initProfTimer();
  95 #endif
  96
  97   return startTicker(ms, handle_tick);
  98 }
  99
 100 int
 101 stopTimer()
 102 {
 103   return stopTicker();
 104 }