Tweak compaction candidate selection to avoid keeping page with low occupancy around.

src/heap-inl.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 420 matching lines @@
     ASSERT(HEAP->InFromSpace(*p));
     *p = dest;
     return;
   }
 
   // Call the slow part of scavenge object.
   return ScavengeObjectSlow(p, object);
 }
 
 
-bool Heap::CollectGarbage(AllocationSpace space) {
-  return CollectGarbage(space, SelectGarbageCollector(space));
+bool Heap::CollectGarbage(AllocationSpace space, const char* gc_reason) {
+  const char* collector_reason = NULL;
+  GarbageCollector collector = SelectGarbageCollector(space, &collector_reason);
+  return CollectGarbage(space, collector, gc_reason, collector_reason);
 }
 
 
 MaybeObject* Heap::PrepareForCompare(String* str) {
   // Always flatten small strings and force flattening of long strings
   // after we have accumulated a certain amount we failed to flatten.
   static const int kMaxAlwaysFlattenLength = 32;
   static const int kFlattenLongThreshold = 16*KB;
 
   const int length = str->length();
@@ skipping 14 matching lines @@
   int amount = amount_of_external_allocated_memory_ + change_in_bytes;
   if (change_in_bytes >= 0) {
     // Avoid overflow.
     if (amount > amount_of_external_allocated_memory_) {
       amount_of_external_allocated_memory_ = amount;
     }
     int amount_since_last_global_gc =
         amount_of_external_allocated_memory_ -
         amount_of_external_allocated_memory_at_last_global_gc_;
     if (amount_since_last_global_gc > external_allocation_limit_) {
-      CollectAllGarbage(kNoGCFlags);
+      CollectAllGarbage(kNoGCFlags, "external memory allocation limit reached");
     }
   } else {
     // Avoid underflow.
     if (amount >= 0) {
       amount_of_external_allocated_memory_ = amount;
     }
   }
   ASSERT(amount_of_external_allocated_memory_ >= 0);
   return amount_of_external_allocated_memory_;
 }
@@ skipping 28 matching lines @@
   do {                                                                    \
     GC_GREEDY_CHECK();                                                    \
     MaybeObject* __maybe_object__ = FUNCTION_CALL;                        \
     Object* __object__ = NULL;                                            \
     if (__maybe_object__->ToObject(&__object__)) RETURN_VALUE;            \
     if (__maybe_object__->IsOutOfMemory()) {                              \
       v8::internal::V8::FatalProcessOutOfMemory("CALL_AND_RETRY_0", true);\
     }                                                                     \
     if (!__maybe_object__->IsRetryAfterGC()) RETURN_EMPTY;                \
     ISOLATE->heap()->CollectGarbage(Failure::cast(__maybe_object__)->     \
-                                    allocation_space());                  \
+                                    allocation_space(),                   \
+                                    "allocation failure");                \
     __maybe_object__ = FUNCTION_CALL;                                     \
     if (__maybe_object__->ToObject(&__object__)) RETURN_VALUE;            \
     if (__maybe_object__->IsOutOfMemory()) {                              \
       v8::internal::V8::FatalProcessOutOfMemory("CALL_AND_RETRY_1", true);\
     }                                                                     \
     if (!__maybe_object__->IsRetryAfterGC()) RETURN_EMPTY;                \
     ISOLATE->counters()->gc_last_resort_from_handles()->Increment();      \
-    ISOLATE->heap()->CollectAllAvailableGarbage();                        \
+    ISOLATE->heap()->CollectAllAvailableGarbage("last resort gc");        \
     {                                                                     \
       AlwaysAllocateScope __scope__;                                      \
       __maybe_object__ = FUNCTION_CALL;                                   \
     }                                                                     \
     if (__maybe_object__->ToObject(&__object__)) RETURN_VALUE;            \
     if (__maybe_object__->IsOutOfMemory() ||                              \
         __maybe_object__->IsRetryAfterGC()) {                             \
       /* TODO(1181417): Fix this. */                                      \
       v8::internal::V8::FatalProcessOutOfMemory("CALL_AND_RETRY_2", true);\
     }                                                                     \
@@ skipping 239 matching lines @@
 AssertNoAllocation::~AssertNoAllocation() { }
 DisableAssertNoAllocation::DisableAssertNoAllocation() { }
 DisableAssertNoAllocation::~DisableAssertNoAllocation() { }
 
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_INL_H_