--- old/src/share/vm/runtime/os.cpp	2016-07-21 12:32:31.055669700 +0200
+++ new/src/share/vm/runtime/os.cpp	2016-07-21 12:32:30.963666931 +0200
@@ -71,6 +71,7 @@
 uintptr_t         os::_serialize_page_mask = 0;
 long              os::_rand_seed          = 1;
 int               os::_processor_count    = 0;
+int               os::_initial_active_processor_count = 0;
 size_t            os::_page_sizes[os::page_sizes_max];
 
 #ifndef PRODUCT
@@ -1759,6 +1760,13 @@
 }
 #endif
 
+void os::set_processor_count(int count) {
+  assert(_processor_count == 0, "Trying to set processor count twice, from %d to %d", _processor_count, count);
+  _processor_count = count;
+  _initial_active_processor_count = active_processor_count();
+  log_trace(os)("Initial active processor count is %d", _initial_active_processor_count);
+}
+
 /////////////// Unit tests ///////////////
 
 #ifndef PRODUCT