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

runtime/vm/scavenger.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/scavenger.h"
 
 #include <algorithm>
 #include <map>
 #include <utility>
 
@@ skipping 55 matching lines @@
 
 
 class ScavengerVisitor : public ObjectPointerVisitor {
  public:
   explicit ScavengerVisitor(Isolate* isolate, Scavenger* scavenger)
       : ObjectPointerVisitor(isolate),
         scavenger_(scavenger),
         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) {}
 
   void VisitPointers(RawObject** first, RawObject** last) {
     for (RawObject** current = first; current <= last; current++) {
       ScavengePointer(current);
     }
   }
 
   GrowableArray<RawObject*>* DelayedWeakStack() {
@@ skipping 14 matching lines @@
     delay_set_.insert(std::make_pair(raw_key, raw_weak));
   }
 
   void Finalize() {
     DelaySet::iterator it = delay_set_.begin();
     for (; it != delay_set_.end(); ++it) {
       WeakProperty::Clear(it->second);
     }
   }
 
+  intptr_t bytes_promoted() { return bytes_promoted_; }
+
  private:
   void UpdateStoreBuffer(RawObject** p, RawObject* obj) {
     uword ptr = reinterpret_cast<uword>(p);
     ASSERT(obj->IsHeapObject());
     ASSERT(!scavenger_->Contains(ptr));
     ASSERT(!heap_->CodeContains(ptr));
     ASSERT(heap_->Contains(ptr));
     // If the newly written object is not a new object, drop it immediately.
     if (!obj->IsNewObject()) return;
     isolate()->store_buffer()->AddPointer(ptr);
@@ skipping 48 matching lines @@
         // Not a survivor of a previous scavenge. Just copy the object into the
         // to space.
         new_addr = scavenger_->TryAllocate(size);
       } else {
         // TODO(iposva): Experiment with less aggressive promotion. For example
         // a coin toss determines if an object is promoted or whether it should
         // survive in this generation.
         //
         // 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);
         }
       }
       // During a scavenge we always succeed to at least copy all of the
       // current objects to the to space.
       ASSERT(new_addr != 0);
       // Copy the object to the new location.
       memmove(reinterpret_cast<void*>(new_addr),
               reinterpret_cast<void*>(raw_addr),
               size);
       // Remember forwarding address.
       ForwardTo(raw_addr, new_addr);
     }
     // Update the reference.
     RawObject* new_obj = RawObject::FromAddr(new_addr);
     *p = new_obj;
     // Update the store buffer as needed.
     if (visiting_old_pointers_) {
       UpdateStoreBuffer(p, new_obj);
     }
   }
 
   Scavenger* scavenger_;
   Heap* heap_;
   Heap* vm_heap_;
   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_;
 
   DISALLOW_COPY_AND_ASSIGN(ScavengerVisitor);
 };
 
 
 class ScavengerWeakVisitor : public HandleVisitor {
  public:
@@ skipping 384 matching lines @@
     OS::PrintErr("Verifying before Scavenge...");
     heap_->Verify();
     OS::PrintErr(" done.\n");
   }
 
   if (FLAG_verbose_gc) {
     OS::PrintErr("Start scavenge for %s collection\n", 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);
   IterateRoots(isolate, &visitor, !invoke_api_callbacks);
   ProcessToSpace(&visitor);
   IterateWeakReferences(isolate, &visitor);
   ScavengerWeakVisitor weak_visitor(this);
   IterateWeakRoots(isolate, &weak_visitor, invoke_api_callbacks);
   visitor.Finalize();
   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) {
     OS::PrintErr("Verifying after Scavenge...");
     heap_->Verify();
     OS::PrintErr(" done.\n");
   }
 
   count_++;
   // Done scavenging. Reset the marker.
@@ skipping 21 matching lines @@
   PeerTable::iterator it = peer_table_.find(raw_obj);
   return (it == peer_table_.end()) ? NULL : it->second;
 }
 
 
 int64_t Scavenger::PeerCount() const {
   return static_cast<int64_t>(peer_table_.size());
 }
 
 }  // namespace dart