Make sweeper threads respect the max_available_threads constraint.

src/heap/heap.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/accessors.h"
 #include "src/api.h"
 #include "src/base/bits.h"
 #include "src/base/once.h"
@@ skipping 124 matching lines @@
       gc_count_at_last_idle_gc_(0),
       full_codegen_bytes_generated_(0),
       crankshaft_codegen_bytes_generated_(0),
       gcs_since_last_deopt_(0),
       allocation_sites_scratchpad_length_(0),
       promotion_queue_(this),
       configured_(false),
       external_string_table_(this),
       chunks_queued_for_free_(NULL),
       gc_callbacks_depth_(0),
-      deserialization_complete_(false) {
+      deserialization_complete_(false),
+      concurrent_sweeping_enabled_(false) {
 // Allow build-time customization of the max semispace size. Building
 // V8 with snapshots and a non-default max semispace size is much
 // easier if you can define it as part of the build environment.
 #if defined(V8_MAX_SEMISPACE_SIZE)
   max_semi_space_size_ = reserved_semispace_size_ = V8_MAX_SEMISPACE_SIZE;
 #endif
 
   // Ensure old_generation_size_ is a multiple of kPageSize.
   DCHECK(MB >= Page::kPageSize);
 
@@ skipping 5298 matching lines @@
   // call Heap::TearDown() to release allocated memory.
   //
   // If the heap is not yet configured (e.g. through the API), configure it.
   // Configuration is based on the flags new-space-size (really the semispace
   // size) and old-space-size if set or the initial values of semispace_size_
   // and old_generation_size_ otherwise.
   if (!configured_) {
     if (!ConfigureHeapDefault()) return false;
   }
 
+  concurrent_sweeping_enabled_ =
+      FLAG_concurrent_sweeping && isolate_->max_available_threads() > 1;
+
   base::CallOnce(&initialize_gc_once, &InitializeGCOnce);
 
   MarkMapPointersAsEncoded(false);
 
   // Set up memory allocator.
   if (!isolate_->memory_allocator()->SetUp(MaxReserved(), MaxExecutableSize()))
     return false;
 
   // Set up new space.
   if (!new_space_.SetUp(reserved_semispace_size_, max_semi_space_size_)) {
@@ skipping 1071 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   CODE_AGE_LIST_COMPLETE(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   MemCopy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   MemCopy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 }
 }  // namespace v8::internal