Fail new space promotions only when old space is truly exhausted.

runtime/vm/scavenger.cc

Index: runtime/vm/scavenger.cc
diff --git a/runtime/vm/scavenger.cc b/runtime/vm/scavenger.cc
index e1b4326d03e6f63e5d76c6d7a4c2771634363322..de4ff2cc5a13e543e0dfb8d2c46f583b1bf3cb22 100644
--- a/runtime/vm/scavenger.cc
+++ b/runtime/vm/scavenger.cc
@@ -73,6 +73,8 @@ class ScavengerVisitor : public ObjectPointerVisitor {
         heap_(scavenger->heap_),
         vm_heap_(Dart::vm_isolate()->heap()),
         delayed_weak_stack_(),
+        growth_policy_(PageSpace::kControlGrowth),
+        bytes_promoted_(0),
         visiting_old_pointers_(false),
         in_scavenge_pointer_(false) {}
 
@@ -107,6 +109,8 @@ class ScavengerVisitor : public ObjectPointerVisitor {
     }
   }
 
+  intptr_t bytes_promoted() { return bytes_promoted_; }
+
  private:
   void UpdateStoreBuffer(RawObject** p, RawObject* obj) {
     uword ptr = reinterpret_cast<uword>(p);
@@ -175,14 +179,28 @@ class ScavengerVisitor : public ObjectPointerVisitor {
         //
         // This object is a survivor of a previous scavenge. Attempt to promote
         // the object.
-        new_addr = heap_->TryAllocate(size, Heap::kOld);
+        new_addr = heap_->old_space()->TryAllocate(size,
+                                                   HeapPage::kData,
+                                                   growth_policy_);
         if (new_addr != 0) {
           // If promotion succeeded then we need to remember it so that it can
           // be traversed later.
+          bytes_promoted_ += size;

[Ivan Posva, 2012/11/14 21:07:18]

Comment above has been separated from the code it refers to.

[cshapiro, 2012/11/14 22:47:36]

I do not follow.  Do you want me to transpose lines 188 and 189?  That is
trivial...

           scavenger_->PushToPromotedStack(new_addr);
+        } else if (!scavenger_->had_promotion_failure_) {
+          // Retry.

[Ivan Posva, 2012/11/14 21:07:18]

Please expand on the "Retry." comment by briefly explaining the state machine.

+          scavenger_->had_promotion_failure_ = true;
+          growth_policy_ = PageSpace::kForceGrowth;
+          new_addr = heap_->old_space()->TryAllocate(size,
+                                                     HeapPage::kData,
+                                                     growth_policy_);
+          if (new_addr != 0) {
+            bytes_promoted_ += size;
+            scavenger_->PushToPromotedStack(new_addr);
+          }

[Ivan Posva, 2012/11/14 21:07:18]

What if new_addr is 0?

[cshapiro, 2012/11/14 22:47:36]

Same thing that always happens.  We trip the assert below in debug mode and
SIGSEGV in release mode because of the invalid memmove destination argument.

         } else {
+          ASSERT(growth_policy_ == PageSpace::kForceGrowth);
           // Promotion did not succeed. Copy into the to space instead.
-          scavenger_->had_promotion_failure_ = true;
           new_addr = scavenger_->TryAllocate(size);
         }
       }
@@ -211,6 +229,8 @@ class ScavengerVisitor : public ObjectPointerVisitor {
   typedef std::multimap<RawObject*, RawWeakProperty*> DelaySet;
   DelaySet delay_set_;
   GrowableArray<RawObject*> delayed_weak_stack_;
+  PageSpace::GrowthPolicy growth_policy_;
+  intptr_t bytes_promoted_;
 
   bool visiting_old_pointers_;
   bool in_scavenge_pointer_;
@@ -615,6 +635,9 @@ void Scavenger::Scavenge(bool invoke_api_callbacks, const char* gc_reason) {
   }
   Timer timer(FLAG_verbose_gc, "Scavenge");
   timer.Start();
+
+  intptr_t in_use_before = in_use();
+
   // Setup the visitor and run a scavenge.
   ScavengerVisitor visitor(isolate, this);
   Prologue(isolate, invoke_api_callbacks);
@@ -627,10 +650,17 @@ void Scavenger::Scavenge(bool invoke_api_callbacks, const char* gc_reason) {
   ProcessPeerReferents();
   Epilogue(isolate, invoke_api_callbacks);
   timer.Stop();
+
   if (FLAG_verbose_gc) {
-    OS::PrintErr("Scavenge[%d]: %"Pd64"us\n",
+    const intptr_t KB2 = KB / 2;
+    OS::PrintErr("Scavenge[%d]: %"Pd64"us (%"Pd"K -> %"Pd"K, %"Pd"K)\n"
+                 "Promoted %"Pd"K\n",
                  count_,
-                 timer.TotalElapsedTime());
+                 timer.TotalElapsedTime(),
+                 (in_use_before + KB2) / KB,
+                 (in_use() + KB2) / KB,
+                 (capacity() + KB2) / KB,
+                 (visitor.bytes_promoted() + KB2) / KB);
   }
 
   if (FLAG_verify_after_gc) {