Remove slots that point to unboxed doubles from the StoreBuffer/SlotsBuffer.

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/code-stubs.h"
 #include "src/compilation-cache.h"
@@ skipping 694 matching lines @@
 
   intptr_t estimated_release = 0;
 
   Candidate candidates[kMaxMaxEvacuationCandidates];
 
   max_evacuation_candidates =
       Min(kMaxMaxEvacuationCandidates, max_evacuation_candidates);
 
   int count = 0;
   int fragmentation = 0;
+  int page_number = 0;
   Candidate* least = NULL;
 
   PageIterator it(space);
   while (it.has_next()) {
     Page* p = it.next();
     if (p->NeverEvacuate()) continue;
 
     // Invariant: Evacuation candidates are just created when marking is
     // started. At the end of a GC all evacuation candidates are cleared and
     // their slot buffers are released.
     CHECK(!p->IsEvacuationCandidate());
     CHECK(p->slots_buffer() == NULL);
 
     if (FLAG_stress_compaction) {
-      unsigned int counter = space->heap()->ms_count();
-      uintptr_t page_number = reinterpret_cast<uintptr_t>(p) >> kPageSizeBits;
-      if ((counter & 1) == (page_number & 1)) fragmentation = 1;
+      if (FLAG_manual_evacuation_candidates_selection) {
+        if (p->IsFlagSet(MemoryChunk::FORCE_EVACUATION_CANDIDATE_FOR_TESTING)) {
+          p->ClearFlag(MemoryChunk::FORCE_EVACUATION_CANDIDATE_FOR_TESTING);
+          fragmentation = 1;
+        }
+      } else {
+        unsigned int counter = space->heap()->ms_count();
+        if ((counter & 1) == (page_number & 1)) fragmentation = 1;
+        page_number++;
+      }
     } else if (mode == REDUCE_MEMORY_FOOTPRINT) {
       // Don't try to release too many pages.
       if (estimated_release >= over_reserved) {
         continue;
       }
 
       intptr_t free_bytes = 0;
 
       if (!p->WasSwept()) {
         free_bytes = (p->area_size() - p->LiveBytes());
@@ skipping 3532 matching lines @@
     buffer = allocator->AllocateBuffer(buffer);
     *buffer_address = buffer;
   }
   DCHECK(buffer->HasSpaceForTypedSlot());
   buffer->Add(reinterpret_cast<ObjectSlot>(type));
   buffer->Add(reinterpret_cast<ObjectSlot>(addr));
   return true;
 }
 
 
+void SlotsBuffer::RemoveSlot(SlotsBuffer* buffer, ObjectSlot slot_to_remove) {

[Hannes Payer (out of office), 2015/03/03 09:48:53]

I think it would be more efficient to just clear the slot instead of moving
everything to the left.

[Igor Sheludko, 2015/03/04 14:54:19]

Done.

+  DCHECK(!IsTypedSlot(slot_to_remove));
+  while (buffer != NULL) {
+    intptr_t written = 0;
+    intptr_t length = buffer->idx_;
+
+    ObjectSlot* slots = buffer->slots_;
+    for (int slot_idx = 0; slot_idx < length; ++slot_idx) {
+      ObjectSlot slot = slots[slot_idx];
+      if (!IsTypedSlot(slot)) {
+        if (slot != slot_to_remove) {
+          if (written != slot_idx) slots[written] = slot;
+          ++written;
+        }
+      } else {
+        ++slot_idx;
+        DCHECK(slot_idx < length);
+        ObjectSlot typed_slot = slots[slot_idx];
+        if (typed_slot != slot_to_remove) {
+          if (written != slot_idx - 1) {
+            slots[written++] = slot;
+            slots[written++] = typed_slot;
+          } else {
+            written += 2;
+          }
+        }
+      }
+    }
+    buffer->idx_ = written;
+    buffer = buffer->next_;
+  }
+}
+
+
 static inline SlotsBuffer::SlotType SlotTypeForRMode(RelocInfo::Mode rmode) {
   if (RelocInfo::IsCodeTarget(rmode)) {
     return SlotsBuffer::CODE_TARGET_SLOT;
   } else if (RelocInfo::IsEmbeddedObject(rmode)) {
     return SlotsBuffer::EMBEDDED_OBJECT_SLOT;
   } else if (RelocInfo::IsDebugBreakSlot(rmode)) {
     return SlotsBuffer::DEBUG_TARGET_SLOT;
   } else if (RelocInfo::IsJSReturn(rmode)) {
     return SlotsBuffer::JS_RETURN_SLOT;
   }
@@ skipping 121 matching lines @@
   SlotsBuffer* buffer = *buffer_address;
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 }
 }  // namespace v8::internal