diff --git a/runtime/vm/compiler/jit/compiler.cc b/runtime/vm/compiler/jit/compiler.cc
index 6e19591..371fafa 100644
--- a/runtime/vm/compiler/jit/compiler.cc
+++ b/runtime/vm/compiler/jit/compiler.cc
@@ -1828,7 +1828,7 @@
   // TODO(srdjan): Checking different strategy for collecting garbage
   // accumulated by background compiler.
   if (isolate_->heap()->NeedsGarbageCollection()) {
-    isolate_->heap()->CollectAllGarbage();
+    isolate_->heap()->CollectMostGarbage();
   }
   {
     MonitorLocker ml(queue_monitor_);
diff --git a/runtime/vm/heap/heap.cc b/runtime/vm/heap/heap.cc
index 9a281b0..de9911f 100644
--- a/runtime/vm/heap/heap.cc
+++ b/runtime/vm/heap/heap.cc
@@ -95,8 +95,9 @@
     if (addr != 0) {
       return addr;
     }
-    // All GC tasks finished without allocating successfully. Run a full GC.
-    CollectAllGarbage();
+    // All GC tasks finished without allocating successfully. Collect both
+    // generations.
+    CollectMostGarbage();
     addr = old_space_.TryAllocate(size, type);
     if (addr != 0) {
       return addr;
@@ -144,7 +145,7 @@
     ASSERT(space == kOld);
     old_space_.AllocateExternal(cid, size);
     if (old_space_.NeedsGarbageCollection()) {
-      CollectAllGarbage(kExternal);
+      CollectMostGarbage(kExternal);
     }
   }
 }
@@ -460,6 +461,12 @@
   }
 }
 
+void Heap::CollectMostGarbage(GCReason reason) {
+  Thread* thread = Thread::Current();
+  CollectNewSpaceGarbage(thread, reason);
+  CollectOldSpaceGarbage(thread, kMarkSweep, reason);
+}
+
 void Heap::CollectAllGarbage(GCReason reason) {
   Thread* thread = Thread::Current();
 
diff --git a/runtime/vm/heap/heap.h b/runtime/vm/heap/heap.h
index d4c2cf1..7f2689d 100644
--- a/runtime/vm/heap/heap.h
+++ b/runtime/vm/heap/heap.h
@@ -114,13 +114,24 @@
   void NotifyIdle(int64_t deadline);
   void NotifyLowMemory();
 
+  // Collect a single generation.
   void CollectGarbage(Space space);
   void CollectGarbage(GCType type, GCReason reason);
+
+  // Collect both generations by performing a scavenge followed by a
+  // mark-sweep. This function may not collect all unreachable objects. Because
+  // mark-sweep treats new space as roots, a cycle between unreachable old and
+  // new objects will not be collected until the new objects are promoted.
+  // Verification based on heap iteration should instead use CollectAllGarbage.
+  void CollectMostGarbage(GCReason reason = kFull);
+
+  // Collect both generations by performing an evacuation followed by a
+  // mark-sweep. This function will collect all unreachable objects.
   void CollectAllGarbage(GCReason reason = kFull);
+
   bool NeedsGarbageCollection() const {
     return old_space_.NeedsGarbageCollection();
   }
-
   void WaitForSweeperTasks(Thread* thread);
 
   // Enables growth control on the page space heaps.  This should be
diff --git a/runtime/vm/stub_code.cc b/runtime/vm/stub_code.cc
index 82e4767..8b1a357 100644
--- a/runtime/vm/stub_code.cc
+++ b/runtime/vm/stub_code.cc
@@ -178,7 +178,7 @@
       }
       Isolate* isolate = thread->isolate();
       if (isolate->heap()->NeedsGarbageCollection()) {
-        isolate->heap()->CollectAllGarbage();
+        isolate->heap()->CollectMostGarbage();
       }
     }
 #ifndef PRODUCT