[heap] Divide available memory upon compaction tasks

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/heap/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/base/sys-info.h"
 #include "src/code-stubs.h"
@@ skipping 590 matching lines @@
     // Any PagedSpace might invoke RefillFreeLists, so we need to make sure
     // to only refill them for the old space.
     return;
   }
 
   intptr_t added = space->free_list()->Concatenate(free_list);
   space->accounting_stats_.IncreaseCapacity(added);
 }
 
 
+void MarkCompactCollector::RefillFreeList(CompactionSpace* space) {

[ulan, 2015/10/09 11:48:48]

Will this function be used in other CL?

[Michael Lippautz, 2015/10/09 12:20:12]

The function should already be used as PagedSpace::SlowAllocateRaw() calls into
RefillFreeList() with {this} being a CompactionSpace.

+  FreeList* free_list = nullptr;
+  if (space->identity() == OLD_SPACE) {
+    free_list = free_list_old_space_.get();
+  } else if (space->identity() == CODE_SPACE) {
+    free_list = free_list_code_space_.get();
+  } else {
+    UNREACHABLE();
+  }
+
+  intptr_t kWantedMemory = 500 * KB;

[ulan, 2015/10/09 11:48:48]

This constant is duplicated below. Let's unify them.

Could you write a comment explaining why 500*KB?

[Michael Lippautz, 2015/10/09 12:20:13]

Unified as MarkCompactCollector::kCompactionMemoryWanted
Nope :) It's an upper bound to somehow limit free list node traversal.  A better
constant would probably consider the number of compaction tasks and be smaller
(?) 

+  intptr_t refilled = 0;
+  while (refilled < kWantedMemory) {
+    FreeSpace* node = free_list->TryRemoveMemory(kWantedMemory - refilled);
+    if (node == nullptr) return;
+    refilled += node->size();
+    space->AddMemory(node->address(), node->size());
+  }
+}
+
+
 void Marking::TransferMark(Heap* heap, Address old_start, Address new_start) {
   // This is only used when resizing an object.
   DCHECK(MemoryChunk::FromAddress(old_start) ==
          MemoryChunk::FromAddress(new_start));
 
   if (!heap->incremental_marking()->IsMarking()) return;
 
   // If the mark doesn't move, we don't check the color of the object.
   // It doesn't matter whether the object is black, since it hasn't changed
   // size, so the adjustment to the live data count will be zero anyway.
@@ skipping 2769 matching lines @@
 
   const int num_tasks = NumberOfParallelCompactionTasks();
 
   // Set up compaction spaces.
   CompactionSpaceCollection** compaction_spaces_for_tasks =
       new CompactionSpaceCollection*[num_tasks];
   for (int i = 0; i < num_tasks; i++) {
     compaction_spaces_for_tasks[i] = new CompactionSpaceCollection(heap());
   }
 
-  compaction_spaces_for_tasks[0]->Get(OLD_SPACE)->MoveOverFreeMemory(
-      heap()->old_space());
-  compaction_spaces_for_tasks[0]
-      ->Get(CODE_SPACE)
-      ->MoveOverFreeMemory(heap()->code_space());
+  const intptr_t kWantedMemory = 500 * KB;

[Michael Lippautz, 2015/10/09 11:08:59]

We could branch in a fast case here  for 1 compaction tasks: Just move over the
free list (i.e. PageSpace::MoveOverMemory()).

+  heap()->old_space()->DivideUponCompactionSpaces(compaction_spaces_for_tasks,
+                                                  num_tasks, kWantedMemory);
+  heap()->code_space()->DivideUponCompactionSpaces(compaction_spaces_for_tasks,
+                                                   num_tasks, kWantedMemory);
 
   compaction_in_progress_ = true;
   // Kick off parallel tasks.
   for (int i = 1; i < num_tasks; i++) {
     concurrent_compaction_tasks_active_++;
     V8::GetCurrentPlatform()->CallOnBackgroundThread(
         new CompactionTask(heap(), compaction_spaces_for_tasks[i]),
         v8::Platform::kShortRunningTask);
   }
 
   // Contribute in main thread. Counter and signal are in principal not needed.
-  concurrent_compaction_tasks_active_++;
   EvacuatePages(compaction_spaces_for_tasks[0], &migration_slots_buffer_);
-  pending_compaction_tasks_semaphore_.Signal();
 
   WaitUntilCompactionCompleted();
 
   // Merge back memory (compacted and unused) from compaction spaces.
   for (int i = 0; i < num_tasks; i++) {
     heap()->old_space()->MergeCompactionSpace(
         compaction_spaces_for_tasks[i]->Get(OLD_SPACE));
     heap()->code_space()->MergeCompactionSpace(
         compaction_spaces_for_tasks[i]->Get(CODE_SPACE));
     delete compaction_spaces_for_tasks[i];
@@ skipping 1172 matching lines @@
     MarkBit mark_bit = Marking::MarkBitFrom(host);
     if (Marking::IsBlack(mark_bit)) {
       RelocInfo rinfo(pc, RelocInfo::CODE_TARGET, 0, host);
       RecordRelocSlot(&rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8