Add a proper way to pass the number of processors to V8

src/api.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 548 matching lines @@
 }
 
 
 ResourceConstraints::ResourceConstraints()
   : max_young_space_size_(0),
     max_old_space_size_(0),
     max_executable_size_(0),
     stack_limit_(NULL),
     max_available_threads_(0) { }
 
-
-void ResourceConstraints::ConfigureDefaults(uint64_t physical_memory) {
+void ResourceConstraints::ConfigureDefaults(uint64_t physical_memory,
+                                            uint32_t number_of_processors) {
   const int lump_of_memory = (i::kPointerSize / 4) * i::MB;
 #if V8_OS_ANDROID
   // Android has higher physical memory requirements before raising the maximum
   // heap size limits since it has no swap space.
   const uint64_t low_limit = 512ul * i::MB;
   const uint64_t medium_limit = 1ul * i::GB;
   const uint64_t high_limit = 2ul * i::GB;
 #else
   const uint64_t low_limit = 512ul * i::MB;
   const uint64_t medium_limit = 768ul * i::MB;
@@ skipping 13 matching lines @@
   } else if (physical_memory <= high_limit) {
     set_max_young_space_size(16 * lump_of_memory);
     set_max_old_space_size(512 * lump_of_memory);
     set_max_executable_size(256 * lump_of_memory);
   } else {
     set_max_young_space_size(16 * lump_of_memory);
     set_max_old_space_size(700 * lump_of_memory);
     set_max_executable_size(256 * lump_of_memory);
   }
 
-  set_max_available_threads(0);
+  set_max_available_threads(i::Max(i::Min(number_of_processors, 4u), 1u));
 }
 
 
+void ResourceConstraints::ConfigureDefaults(uint64_t physical_memory) {
+  ConfigureDefaults(physical_memory, i::CPU::NumberOfProcessorsOnline());
+}
+
+
 bool SetResourceConstraints(ResourceConstraints* constraints) {
   i::Isolate* isolate = EnterIsolateIfNeeded();
   return SetResourceConstraints(reinterpret_cast<Isolate*>(isolate),
                                 constraints);
 }
 
 
 bool SetResourceConstraints(Isolate* v8_isolate,
                             ResourceConstraints* constraints) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(v8_isolate);
@@ skipping 7044 matching lines @@
   Isolate* isolate = reinterpret_cast<Isolate*>(info.GetIsolate());
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 } }  // namespace v8::internal