[heap] Divide available memory upon compaction tasks

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index e26653495ecf2ae7ff6bb9211798212dec8cbc1b..2770546955453cc36cad8f2c3ccec81d971083be 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -608,6 +608,27 @@ void MarkCompactCollector::RefillFreeList(PagedSpace* space) {
 }
 
 
+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) ==
@@ -3397,11 +3418,11 @@ void MarkCompactCollector::EvacuatePagesInParallel() {
     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.
@@ -3413,9 +3434,7 @@ void MarkCompactCollector::EvacuatePagesInParallel() {
   }
 
   // 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();