[sgen] Number of major objects marked in concurrent DTrace probes.

Can be enabled/disabled via #define in sgen-conf.h.  Disabled by default
because it's a small performance hit.

data/mono.d

@@ -20,10 +20,10 @@ provider mono {
 	probe gc__end (int generation);
 
 	probe gc__concurrent__start__begin (int generation);
-	probe gc__concurrent__start__end (int generation);
-	probe gc__concurrent__update__finish__begin (int generation);
-	probe gc__concurrent__update__end (int generation);
-	probe gc__concurrent__finish__end (int generation);
+	probe gc__concurrent__start__end (int generation, long long num_major_objects_marked);
+	probe gc__concurrent__update__finish__begin (int generation, long long num_major_objects_marked);
+	probe gc__concurrent__update__end (int generation, long long num_major_objects_marked);
+	probe gc__concurrent__finish__end (int generation, long long num_major_objects_marked);
 
 	probe gc__sweep__begin (int generation, int full_sweep);
 	probe gc__sweep__end (int generation, int full_sweep);

mono/metadata/sgen-conf.h

@@ -75,6 +75,13 @@ typedef guint64 mword;
  */
 //#define XDOMAIN_CHECKS_IN_WBARRIER
 
+/*
+ * Define this to get number of objects marked information in the
+ * concurrent GC DTrace probes.  Has a small performance impact, so
+ * it's disabled by default.
+ */
+//#define SGEN_COUNT_NUMBER_OF_MAJOR_OBJECTS_MARKED
+
 #ifndef SGEN_BINARY_PROTOCOL
 #ifndef HEAVY_STATISTICS
 #define MANAGED_ALLOCATION

mono/metadata/sgen-gc.c

@@ -3079,6 +3079,11 @@ major_do_collection (const char *reason)
 	TV_DECLARE (all_btv);
 	int old_next_pin_slot;
 
+	if (major_collector.get_and_reset_num_major_objects_marked) {
+		long long num_marked = major_collector.get_and_reset_num_major_objects_marked ();
+		g_assert (!num_marked);
+	}
+
 	/* world must be stopped already */
 	TV_GETTIME (all_atv);
 
@@ -3088,6 +3093,10 @@ major_do_collection (const char *reason)
 	TV_GETTIME (all_btv);
 	gc_stats.major_gc_time_usecs += TV_ELAPSED (all_atv, all_btv);
 
+	/* FIXME: also report this to the user, preferably in gc-end. */
+	if (major_collector.get_and_reset_num_major_objects_marked)
+		major_collector.get_and_reset_num_major_objects_marked ();
+
 	return bytes_pinned_from_failed_allocation > 0;
 }
 
@@ -3096,6 +3105,10 @@ static gboolean major_do_collection (const char *reason);
 static void
 major_start_concurrent_collection (const char *reason)
 {
+	long long num_objects_marked = major_collector.get_and_reset_num_major_objects_marked ();
+
+	g_assert (num_objects_marked == 0);
+
 	MONO_GC_CONCURRENT_START_BEGIN (GENERATION_OLD);
 
 	// FIXME: store reason and pass it when finishing
@@ -3104,15 +3117,16 @@ major_start_concurrent_collection (const char *reason)
 	gray_queue_redirect (&gray_queue);
 	sgen_workers_wait_for_jobs ();
 
-	MONO_GC_CONCURRENT_START_END (GENERATION_OLD);
+	num_objects_marked = major_collector.get_and_reset_num_major_objects_marked ();
+	MONO_GC_CONCURRENT_START_END (GENERATION_OLD, num_objects_marked);
 
 	current_collection_generation = -1;
 }
 
 static gboolean
 major_update_or_finish_concurrent_collection (gboolean force_finish)
 {
-	MONO_GC_CONCURRENT_UPDATE_FINISH_BEGIN (GENERATION_OLD);
+	MONO_GC_CONCURRENT_UPDATE_FINISH_BEGIN (GENERATION_OLD, major_collector.get_and_reset_num_major_objects_marked ());
 
 	g_assert (sgen_gray_object_queue_is_empty (&gray_queue));
 	if (!have_non_collection_major_object_remembers)
@@ -3122,7 +3136,7 @@ major_update_or_finish_concurrent_collection (gboolean force_finish)
 	sgen_los_update_cardtable_mod_union ();
 
 	if (!force_finish && !sgen_workers_all_done ()) {
-		MONO_GC_CONCURRENT_UPDATE_END (GENERATION_OLD);
+		MONO_GC_CONCURRENT_UPDATE_END (GENERATION_OLD, major_collector.get_and_reset_num_major_objects_marked ());
 		return FALSE;
 	}
 
@@ -3132,7 +3146,7 @@ major_update_or_finish_concurrent_collection (gboolean force_finish)
 	current_collection_generation = GENERATION_OLD;
 	major_finish_collection ("finishing", -1, TRUE);
 
-	MONO_GC_CONCURRENT_FINISH_END (GENERATION_OLD);
+	MONO_GC_CONCURRENT_FINISH_END (GENERATION_OLD, major_collector.get_and_reset_num_major_objects_marked ());
 
 	current_collection_generation = -1;
 

mono/metadata/sgen-gc.h

@@ -720,6 +720,7 @@ struct _SgenMajorCollector {
 	void (*reset_worker_data) (void *data);
 	gboolean (*is_valid_object) (char *object);
 	gboolean (*describe_pointer) (char *pointer);
+	long long (*get_and_reset_num_major_objects_marked) (void);
 };
 
 extern SgenMajorCollector major_collector;

mono/metadata/sgen-marksweep.c

@@ -219,6 +219,14 @@ static long long stat_major_blocks_freed = 0;
 static long long stat_major_blocks_lazy_swept = 0;
 static long long stat_major_objects_evacuated = 0;
 
+static long long num_major_objects_marked = 0;
+
+#ifdef SGEN_COUNT_NUMBER_OF_MAJOR_OBJECTS_MARKED
+#define INC_NUM_MAJOR_OBJECTS_MARKED()	(++num_major_objects_marked)
+#else
+#define INC_NUM_MAJOR_OBJECTS_MARKED()
+#endif
+
 static void
 sweep_block (MSBlockInfo *block);
 
@@ -712,6 +720,7 @@ alloc_obj (MonoVTable *vtable, int size, gboolean pinned, gboolean has_reference
 		MS_CALC_MARK_BIT (word, bit, obj);
 		MS_SET_MARK_BIT (block, word, bit);
 		binary_protocol_mark (obj, NULL, size);
+		INC_NUM_MAJOR_OBJECTS_MARKED ();
 	}
 #endif
 
@@ -1023,6 +1032,7 @@ major_dump_heap (FILE *heap_dump_file)
 			if ((block)->has_references)			\
 				GRAY_OBJECT_ENQUEUE ((queue), (obj));	\
 			binary_protocol_mark ((obj), (gpointer)LOAD_VTABLE ((obj)), sgen_safe_object_get_size ((MonoObject*)(obj))); \
+			INC_NUM_MAJOR_OBJECTS_MARKED ();		\
 		}							\
 	} while (0)
 #define MS_MARK_OBJECT_AND_ENQUEUE(obj,block,queue) do {		\
@@ -1034,6 +1044,7 @@ major_dump_heap (FILE *heap_dump_file)
 			if ((block)->has_references)			\
 				GRAY_OBJECT_ENQUEUE ((queue), (obj));	\
 			binary_protocol_mark ((obj), (gpointer)LOAD_VTABLE ((obj)), sgen_safe_object_get_size ((MonoObject*)(obj))); \
+			INC_NUM_MAJOR_OBJECTS_MARKED ();		\
 		}							\
 	} while (0)
 #define MS_PAR_MARK_OBJECT_AND_ENQUEUE(obj,block,queue) do {		\
@@ -1046,6 +1057,7 @@ major_dump_heap (FILE *heap_dump_file)
 			if ((block)->has_references)			\
 				GRAY_OBJECT_ENQUEUE ((queue), (obj));	\
 			binary_protocol_mark ((obj), (gpointer)LOAD_VTABLE ((obj)), sgen_safe_object_get_size ((MonoObject*)(obj))); \
+			INC_NUM_MAJOR_OBJECTS_MARKED ();		\
 		}							\
 	} while (0)
 
@@ -1252,6 +1264,7 @@ major_copy_or_mark_object (void **ptr, SgenGrayQueue *queue)
 			sgen_los_pin_object (obj);
 			/* FIXME: only enqueue if object has references */
 			GRAY_OBJECT_ENQUEUE (queue, obj);
+			INC_NUM_MAJOR_OBJECTS_MARKED ();
 		}
 	}
 }
@@ -1391,6 +1404,16 @@ major_copy_or_mark_object (void **ptr, SgenGrayQueue *queue)
 #endif
 #endif
 
+#ifdef SGEN_CONCURRENT_MARK
+static long long
+major_get_and_reset_num_major_objects_marked (void)
+{
+	long long num = num_major_objects_marked;
+	num_major_objects_marked = 0;
+	return num;
+}
+#endif
+
 #include "sgen-major-scan-object.h"
 
 static void
@@ -2278,6 +2301,7 @@ sgen_marksweep_init
 #endif
 #ifdef SGEN_CONCURRENT_MARK
 	collector->is_concurrent = TRUE;
+	collector->get_and_reset_num_major_objects_marked = major_get_and_reset_num_major_objects_marked;
 #else
 	collector->is_concurrent = FALSE;
 #endif