From: Vlad Brezae <brezaevlad@gmail.com>
Date: Wed, 28 Oct 2015 20:29:11 +0000 (+0200)
Subject: [sgen] Finish concurrent collection if the heap grows too much
X-Git-Url: http://wien.tomnetworks.com/gitweb/?a=commitdiff_plain;h=7b05a82b56a69a288baa4e7b98f05b98097ca9d7;p=mono.git

[sgen] Finish concurrent collection if the heap grows too much

In order to achieve this, when asked to do a major collection, we finish the concurrent collection immediately, regardless if we are explicitely requested or not to wait_to_finish.
---

diff --git a/mono/sgen/sgen-conf.h b/mono/sgen/sgen-conf.h
index 11a8998478e..5a0e871e22f 100644
--- a/mono/sgen/sgen-conf.h
+++ b/mono/sgen/sgen-conf.h
@@ -190,6 +190,12 @@ typedef mword SgenDescriptor;
  */
 #define SGEN_DEFAULT_ALLOWANCE_HEAP_SIZE_RATIO 0.33
 
+/*
+ * How much more we allow the heap to grow, relative to the allowance, while doing
+ * a concurrent collection, before forcing its finish.
+ */
+#define SGEN_DEFAULT_CONCURRENT_HEAP_ALLOWANCE_RATIO 0.25
+
 /*
  * Default ratio of memory we want to release in a major collection in relation to the the current heap size.
  *
diff --git a/mono/sgen/sgen-gc.c b/mono/sgen/sgen-gc.c
index 9a8d10806da..6dd730dcbe9 100644
--- a/mono/sgen/sgen-gc.c
+++ b/mono/sgen/sgen-gc.c
@@ -2182,7 +2182,7 @@ sgen_ensure_free_space (size_t size)
 				generation_to_collect = GENERATION_OLD;
 			}
 		} else if (sgen_need_major_collection (size)) {
-			reason = "Minor allowance";
+			reason = concurrent_collection_in_progress ? "Forced finish concurrent collection" : "Minor allowance";
 			generation_to_collect = GENERATION_OLD;
 		} else {
 			generation_to_collect = GENERATION_NURSERY;
@@ -2229,18 +2229,18 @@ sgen_perform_collection (size_t requested_size, int generation_to_collect, const
 
 	if (concurrent_collection_in_progress) {
 		/*
-		 * We update the concurrent collection.  If it finished, we're done.  If
-		 * not, and we've been asked to do a nursery collection, we do that.
+		 * If the concurrent worker is finished or we are asked to do a major collection
+		 * then we finish the concurrent collection.
 		 */
-		gboolean finish = major_should_finish_concurrent_collection () || (wait_to_finish && generation_to_collect == GENERATION_OLD);
+		gboolean finish = major_should_finish_concurrent_collection () || generation_to_collect == GENERATION_OLD;
 
 		if (finish) {
 			major_finish_concurrent_collection (wait_to_finish);
 			oldest_generation_collected = GENERATION_OLD;
 		} else {
+			SGEN_ASSERT (0, generation_to_collect == GENERATION_NURSERY, "Why aren't we finishing the concurrent collection?");
 			major_update_concurrent_collection ();
-			if (generation_to_collect == GENERATION_NURSERY)
-				collect_nursery (NULL, FALSE);
+			collect_nursery (NULL, FALSE);
 		}
 
 		goto done;
diff --git a/mono/sgen/sgen-memory-governor.c b/mono/sgen/sgen-memory-governor.c
index 824d2f7183c..ce34f7f4a67 100644
--- a/mono/sgen/sgen-memory-governor.c
+++ b/mono/sgen/sgen-memory-governor.c
@@ -112,13 +112,32 @@ sgen_memgov_calculate_minor_collection_allowance (void)
 	}
 }
 
+static inline size_t
+get_heap_size (void)
+{
+	return major_collector.get_num_major_sections () * major_collector.section_size + los_memory_usage;
+}
+
 gboolean
 sgen_need_major_collection (mword space_needed)
 {
 	size_t heap_size;
 
-	if (sgen_concurrent_collection_in_progress ())
+	if (sgen_concurrent_collection_in_progress ()) {
+		heap_size = get_heap_size ();
+
+		if (heap_size <= major_collection_trigger_size)
+			return FALSE; 
+
+		/* We allow the heap to grow an additional third of the allowance during a concurrent collection */
+		if ((heap_size - major_collection_trigger_size) >
+				(major_collection_trigger_size
+				* (SGEN_DEFAULT_ALLOWANCE_HEAP_SIZE_RATIO / (SGEN_DEFAULT_ALLOWANCE_HEAP_SIZE_RATIO + 1))
+				* SGEN_DEFAULT_CONCURRENT_HEAP_ALLOWANCE_RATIO)) {
+			return TRUE;
+		}
 		return FALSE;
+	}
 
 	/* FIXME: This is a cop-out.  We should have some way of figuring this out. */
 	if (!major_collector.have_swept ())
@@ -129,7 +148,7 @@ sgen_need_major_collection (mword space_needed)
 
 	sgen_memgov_calculate_minor_collection_allowance ();
 
-	heap_size = major_collector.get_num_major_sections () * major_collector.section_size + los_memory_usage;
+	heap_size = get_heap_size ();
 
 	return heap_size > major_collection_trigger_size;
 }
@@ -150,7 +169,7 @@ sgen_memgov_major_collection_start (void)
 	need_calculate_minor_collection_allowance = TRUE;
 
 	if (debug_print_allowance) {
-		SGEN_LOG (0, "Starting collection with heap size %ld bytes", (long)(major_collector.get_num_major_sections () * major_collector.section_size + los_memory_usage));
+		SGEN_LOG (0, "Starting collection with heap size %ld bytes", (long)get_heap_size ());
 	}
 }