[heap] Bound number of tasks by embedder limit instead of artificially capping

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 317 matching lines @@
   }
 };
 
 }  // namespace
 #endif  // VERIFY_HEAP
 
 // =============================================================================
 // MarkCompactCollectorBase, MinorMarkCompactCollector, MarkCompactCollector
 // =============================================================================
 
-int MarkCompactCollectorBase::NumberOfParallelCompactionTasks(
-    int pages, intptr_t live_bytes) {
+int MarkCompactCollectorBase::NumberOfParallelCompactionTasks(int pages) {
   if (!FLAG_parallel_compaction) return 1;
-  // Compute the number of needed tasks based on a target compaction time, the
-  // profiled compaction speed and marked live memory.
-  //
-  // The number of parallel compaction tasks is limited by:
-  // - #evacuation pages
-  // - #cores
-  const double kTargetCompactionTimeInMs = .5;
-
-  double compaction_speed =
-      heap()->tracer()->CompactionSpeedInBytesPerMillisecond();

[Michael Lippautz, 2017/05/10 14:38:40]

I will get rid of this one if we decide to keep it that simple.

-
   const int available_cores = Max(
       1, static_cast<int>(
              V8::GetCurrentPlatform()->NumberOfAvailableBackgroundThreads()));
-  int tasks;
-  if (compaction_speed > 0) {
-    tasks = 1 + static_cast<int>(live_bytes / compaction_speed /
-                                 kTargetCompactionTimeInMs);
-  } else {
-    tasks = pages;
-  }
-  const int tasks_capped_pages = Min(pages, tasks);
-  return Min(available_cores, tasks_capped_pages);
+  return Min(available_cores, pages);
+}
+
+int MarkCompactCollectorBase::NumberOfPointerUpdateTasks(int pages) {
+  if (!FLAG_parallel_pointer_update) return 1;
+  const int available_cores = Max(
+      1, static_cast<int>(
+             V8::GetCurrentPlatform()->NumberOfAvailableBackgroundThreads()));
+  return Min(available_cores, pages);
 }
 
 MarkCompactCollector::MarkCompactCollector(Heap* heap)
     : MarkCompactCollectorBase(heap),
       page_parallel_job_semaphore_(0),
 #ifdef DEBUG
       state_(IDLE),
 #endif
       was_marked_incrementally_(false),
       evacuation_(false),
@@ skipping 3363 matching lines @@
     compaction_speed = heap()->tracer()->CompactionSpeedInBytesPerMillisecond();
   }
 
   const bool profiling =
       heap()->isolate()->is_profiling() ||
       heap()->isolate()->logger()->is_logging_code_events() ||
       heap()->isolate()->heap_profiler()->is_tracking_object_moves();
   ProfilingMigrationObserver profiling_observer(heap());
 
   const int wanted_num_tasks =
-      NumberOfParallelCompactionTasks(job->NumberOfPages(), live_bytes);
+      NumberOfParallelCompactionTasks(job->NumberOfPages());
   Evacuator** evacuators = new Evacuator*[wanted_num_tasks];
   for (int i = 0; i < wanted_num_tasks; i++) {
     evacuators[i] = new Evacuator(collector, record_visitor);
     if (profiling) evacuators[i]->AddObserver(&profiling_observer);
     if (migration_observer != nullptr)
       evacuators[i]->AddObserver(migration_observer);
   }
   job->Run(wanted_num_tasks, [evacuators](int i) { return evacuators[i]; });
   const Address top = heap()->new_space()->top();
   for (int i = 0; i < wanted_num_tasks; i++) {
@@ skipping 497 matching lines @@
       if (ObjectMarking::IsBlack(heap_object,
                                  collector->marking_state(heap_object)))
         return KEEP_SLOT;
     } else {
       DCHECK(!heap->InNewSpace(slot_reference));
     }
     return REMOVE_SLOT;
   }
 };
 
-int NumberOfPointerUpdateTasks(int pages) {
-  if (!FLAG_parallel_pointer_update) return 1;
-  const int available_cores = Max(
-      1, static_cast<int>(
-             V8::GetCurrentPlatform()->NumberOfAvailableBackgroundThreads()));
-  const int kPagesPerTask = 4;
-  return Min(available_cores, (pages + kPagesPerTask - 1) / kPagesPerTask);
-}
-
 template <RememberedSetType type>
 void UpdatePointersInParallel(Heap* heap, base::Semaphore* semaphore,
                               const MarkCompactCollectorBase* collector) {
   PageParallelJob<PointerUpdateJobTraits<type> > job(
       heap, heap->isolate()->cancelable_task_manager(), semaphore);
   RememberedSet<type>::IterateMemoryChunks(
       heap, [&job](MemoryChunk* chunk) { job.AddPage(chunk, 0); });
   int num_pages = job.NumberOfPages();
   int num_tasks = NumberOfPointerUpdateTasks(num_pages);
   job.Run(num_tasks, [collector](int i) { return collector; });
@@ skipping 354 matching lines @@
       // The target is always in old space, we don't have to record the slot in
       // the old-to-new remembered set.
       DCHECK(!heap()->InNewSpace(target));
       RecordRelocSlot(host, &rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8