Copy-on-write class table for concurrent reading.

runtime/vm/pages.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/pages.h"
 
 #include "platform/assert.h"
 #include "vm/compiler_stats.h"
 #include "vm/gc_marker.h"
 #include "vm/gc_sweeper.h"
@@ skipping 715 matching lines @@
 
   // Wait for pending tasks to complete and then account for the driver task.
   {
     MonitorLocker locker(tasks_lock());
     while (tasks() > 0) {
       locker.Wait();
     }
     set_tasks(1);
   }
 
+  // Perform various cleanup that relies on no tasks interfering.
+  isolate->class_table()->FreeOldTables();
+
   NoHandleScope no_handles(isolate);
 
   if (FLAG_print_free_list_before_gc) {
     OS::Print("Data Freelist (before GC):\n");
     freelist_[HeapPage::kData].Print();
     OS::Print("Executable Freelist (before GC):\n");
     freelist_[HeapPage::kExecutable].Print();
   }
 
   if (FLAG_verify_before_gc) {
@@ skipping 356 matching lines @@
     return 0;
   } else {
     ASSERT(total_time >= gc_time);
     int result = static_cast<int>((static_cast<double>(gc_time) /
                                    static_cast<double>(total_time)) * 100);
     return result;
   }
 }
 
 }  // namespace dart