Refactoring and tidy up

This is a port of some of the changes from my private local-GC branch
(which is still in darcs, I haven't converted it to git yet).  There
are a couple of small functional differences in the GC stats: first,
per-thread GC timings should now be more accurate, and secondly we now
report average and maximum pause times. e.g. from minimax +RTS -N8 -s:

                                    Tot time (elapsed)  Avg pause  Max pause
  Gen  0      2755 colls,  2754 par   13.16s    0.93s     0.0003s    0.0150s
  Gen  1       769 colls,   769 par    3.71s    0.26s     0.0003s    0.0059s

rts/Capability.c

@@ -842,51 +842,41 @@ freeCapabilities (void)
    ------------------------------------------------------------------------ */
 
 void
-markSomeCapabilities (evac_fn evac, void *user, nat i0, nat delta, 
-                      rtsBool no_mark_sparks USED_IF_THREADS)
+markCapability (evac_fn evac, void *user, Capability *cap,
+                rtsBool no_mark_sparks USED_IF_THREADS)
 {
-    nat i;
-    Capability *cap;
     InCall *incall;
 
     // Each GC thread is responsible for following roots from the
     // Capability of the same number.  There will usually be the same
     // or fewer Capabilities as GC threads, but just in case there
     // are more, we mark every Capability whose number is the GC
     // thread's index plus a multiple of the number of GC threads.
-    for (i = i0; i < n_capabilities; i += delta) {
-	cap = &capabilities[i];
-	evac(user, (StgClosure **)(void *)&cap->run_queue_hd);
-	evac(user, (StgClosure **)(void *)&cap->run_queue_tl);
+    evac(user, (StgClosure **)(void *)&cap->run_queue_hd);
+    evac(user, (StgClosure **)(void *)&cap->run_queue_tl);
 #if defined(THREADED_RTS)
-        evac(user, (StgClosure **)(void *)&cap->inbox);
+    evac(user, (StgClosure **)(void *)&cap->inbox);
 #endif
-	for (incall = cap->suspended_ccalls; incall != NULL; 
-	     incall=incall->next) {
-	    evac(user, (StgClosure **)(void *)&incall->suspended_tso);
-	}
+    for (incall = cap->suspended_ccalls; incall != NULL;
+         incall=incall->next) {
+        evac(user, (StgClosure **)(void *)&incall->suspended_tso);
+    }
 
 #if defined(THREADED_RTS)
-        if (!no_mark_sparks) {
-            traverseSparkQueue (evac, user, cap);
-        }
-#endif
+    if (!no_mark_sparks) {
+        traverseSparkQueue (evac, user, cap);
     }
+#endif
 
-#if !defined(THREADED_RTS)
-    evac(user, (StgClosure **)(void *)&blocked_queue_hd);
-    evac(user, (StgClosure **)(void *)&blocked_queue_tl);
-    evac(user, (StgClosure **)(void *)&sleeping_queue);
-#endif 
+    // Free STM structures for this Capability
+    stmPreGCHook(cap);
 }
 
 void
 markCapabilities (evac_fn evac, void *user)
 {
-    markSomeCapabilities(evac, user, 0, 1, rtsFalse);
+    nat n;
+    for (n = 0; n < n_capabilities; n++) {
+        markCapability(evac, user, &capabilities[n], rtsFalse);
+    }
 }
-
-/* -----------------------------------------------------------------------------
-   Messages
-   -------------------------------------------------------------------------- */
-

rts/Capability.h

@@ -278,9 +278,11 @@ INLINE_HEADER void contextSwitchCapability(Capability *cap);
 void freeCapabilities (void);
 
 // For the GC:
-void markSomeCapabilities (evac_fn evac, void *user, nat i0, nat delta, 
-                           rtsBool no_mark_sparks);
+void markCapability (evac_fn evac, void *user, Capability *cap,
+                     rtsBool no_mark_sparks USED_IF_THREADS);
+
 void markCapabilities (evac_fn evac, void *user);
+
 void traverseSparkQueues (evac_fn evac, void *user);
 
 /* -----------------------------------------------------------------------------

rts/STM.c

@@ -879,17 +879,12 @@ static StgBool check_read_only(StgTRecHeader *trec STG_UNUSED) {
 
 /************************************************************************/
 
-void stmPreGCHook() {
-  nat i;
-
+void stmPreGCHook (Capability *cap) {
   lock_stm(NO_TREC);
   TRACE("stmPreGCHook");
-  for (i = 0; i < n_capabilities; i ++) {
-    Capability *cap = &capabilities[i];
-    cap -> free_tvar_watch_queues = END_STM_WATCH_QUEUE;
-    cap -> free_trec_chunks = END_STM_CHUNK_LIST;
-    cap -> free_trec_headers = NO_TREC;
-  }
+  cap->free_tvar_watch_queues = END_STM_WATCH_QUEUE;
+  cap->free_trec_chunks = END_STM_CHUNK_LIST;
+  cap->free_trec_headers = NO_TREC;
   unlock_stm(NO_TREC);
 }
 

rts/STM.h

@@ -48,7 +48,7 @@
    --------------
 */
 
-void stmPreGCHook(void);
+void stmPreGCHook(Capability *cap);
 
 /*----------------------------------------------------------------------
 

rts/Schedule.c

@@ -2069,6 +2069,16 @@ freeScheduler( void )
 #endif
 }
 
+void markScheduler (evac_fn evac USED_IF_NOT_THREADS, 
+                    void *user USED_IF_NOT_THREADS)
+{
+#if !defined(THREADED_RTS)
+    evac(user, (StgClosure **)(void *)&blocked_queue_hd);
+    evac(user, (StgClosure **)(void *)&blocked_queue_tl);
+    evac(user, (StgClosure **)(void *)&sleeping_queue);
+#endif 
+}
+
 /* -----------------------------------------------------------------------------
    performGC
 

rts/Schedule.h

@@ -23,6 +23,7 @@
 void initScheduler (void);
 void exitScheduler (rtsBool wait_foreign);
 void freeScheduler (void);
+void markScheduler (evac_fn evac, void *user);
 
 // Place a new thread on the run queue of the current Capability
 void scheduleThread (Capability *cap, StgTSO *tso);