ghc/rts/Timer.c

   1 /* -----------------------------------------------------------------------------
   2  *
   3  * (c) The GHC Team, 1995-2005
   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 "Ticker.h"
  23 #include "Capability.h"
  24
  25 /* ticks left before next pre-emptive context switch */
  26 static int ticks_to_ctxt_switch = 0;
  27
  28 #if defined(THREADED_RTS)
  29 /* idle ticks left before we perform a GC */
  30 static int ticks_to_gc = 0;
  31 #endif
  32
  33 /*
  34  * Function: handle_tick()
  35  *
  36  * At each occurrence of a tick, the OS timer will invoke
  37  * handle_tick().
  38  */
  39 static
  40 void
  41 handle_tick(int unused STG_UNUSED)
  42 {
  43 #ifdef PROFILING
  44   handleProfTick();
  45 #endif
  46   if (RtsFlags.ConcFlags.ctxtSwitchTicks > 0) {
  47       ticks_to_ctxt_switch--;
  48       if (ticks_to_ctxt_switch <= 0) {
  49           ticks_to_ctxt_switch = RtsFlags.ConcFlags.ctxtSwitchTicks;
  50           context_switch = 1;   /* schedule a context switch */
  51
  52 #if defined(THREADED_RTS)
  53           /*
  54            * If we've been inactive for idleGCDelayTicks (set by +RTS
  55            * -I), tell the scheduler to wake up and do a GC, to check
  56            * for threads that are deadlocked.
  57            */
  58           switch (recent_activity) {
  59           case ACTIVITY_YES:
  60               recent_activity = ACTIVITY_MAYBE_NO;
  61               ticks_to_gc = RtsFlags.GcFlags.idleGCDelayTicks;
  62               break;
  63           case ACTIVITY_MAYBE_NO:
  64               if (ticks_to_gc == 0) break; /* 0 ==> no idle GC */
  65               ticks_to_gc--;
  66               if (ticks_to_gc == 0) {
  67                   ticks_to_gc = RtsFlags.GcFlags.idleGCDelayTicks;
  68                   recent_activity = ACTIVITY_INACTIVE;
  69                   blackholes_need_checking = rtsTrue;
  70                   /* hack: re-use the blackholes_need_checking flag */
  71
  72                   /* ToDo: this doesn't work.  Can't invoke
  73                    * pthread_cond_signal from a signal handler.
  74                    * Furthermore, we can't prod a capability that we
  75                    * might be holding.  What can we do?
  76                    */
  77                   prodOneCapability();
  78               }
  79               break;
  80           default:
  81               break;
  82           }
  83 #endif
  84       }
  85   }
  86 }
  87
  88 int
  89 startTimer(nat ms)
  90 {
  91 #ifdef PROFILING
  92   initProfTimer();
  93 #endif
  94
  95   return startTicker(ms, handle_tick);
  96 }
  97
  98 int
  99 stopTimer()
 100 {
 101   return stopTicker();
 102 }