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 #if !defined(mingw32_HOST_OS)
  26 #include "Itimer.h"
  27 #else
  28 #include "win32/Ticker.h"
  29 #endif
  30
  31 /* ticks left before next pre-emptive context switch */
  32 static int ticks_to_ctxt_switch = 0;
  33
  34 #if defined(THREADED_RTS)
  35 /* idle ticks left before we perform a GC */
  36 static int ticks_to_gc = 0;
  37 #endif
  38
  39 /*
  40  * Function: handle_tick()
  41  *
  42  * At each occurrence of a tick, the OS timer will invoke
  43  * handle_tick().
  44  */
  45 static
  46 void
  47 handle_tick(int unused STG_UNUSED)
  48 {
  49 #ifdef PROFILING
  50   handleProfTick();
  51 #endif
  52   if (RtsFlags.ConcFlags.ctxtSwitchTicks > 0) {
  53       ticks_to_ctxt_switch--;
  54       if (ticks_to_ctxt_switch <= 0) {
  55           ticks_to_ctxt_switch = RtsFlags.ConcFlags.ctxtSwitchTicks;
  56           context_switch = 1;   /* schedule a context switch */
  57
  58 #if defined(THREADED_RTS)
  59           /*
  60            * If we've been inactive for idleGCDelayTicks (set by +RTS
  61            * -I), tell the scheduler to wake up and do a GC, to check
  62            * for threads that are deadlocked.
  63            */
  64           switch (recent_activity) {
  65           case ACTIVITY_YES:
  66               recent_activity = ACTIVITY_MAYBE_NO;
  67               ticks_to_gc = RtsFlags.GcFlags.idleGCDelayTicks;
  68               break;
  69           case ACTIVITY_MAYBE_NO:
  70               if (ticks_to_gc == 0) break; /* 0 ==> no idle GC */
  71               ticks_to_gc--;
  72               if (ticks_to_gc == 0) {
  73                   ticks_to_gc = RtsFlags.GcFlags.idleGCDelayTicks;
  74                   recent_activity = ACTIVITY_INACTIVE;
  75                   blackholes_need_checking = rtsTrue;
  76                   /* hack: re-use the blackholes_need_checking flag */
  77
  78                   /* ToDo: this doesn't work.  Can't invoke
  79                    * pthread_cond_signal from a signal handler.
  80                    * Furthermore, we can't prod a capability that we
  81                    * might be holding.  What can we do?
  82                    */
  83                   prodOneCapability();
  84               }
  85               break;
  86           default:
  87               break;
  88           }
  89 #endif
  90       }
  91   }
  92 }
  93
  94 int
  95 startTimer(nat ms)
  96 {
  97 #ifdef PROFILING
  98   initProfTimer();
  99 #endif
 100
 101   return startTicker(ms, handle_tick);
 102 }
 103
 104 int
 105 stopTimer()
 106 {
 107   return stopTicker();
 108 }