src/share/vm/memory/sharedHeap.cpp

rev 4551 : 8015237: Parallelize string table scanning during strong root processing
Summary: Parallelize the scanning of the intern string table by having each GC worker claim a given number of buckets. Changes were also reviewed by Per Liden <per.liden@oracle.com>.
Reviewed-by: tschatzl, stefank, twisti

@@ -1,7 +1,7 @@
 /*
- * Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.

@@ -44,11 +44,10 @@
   SH_PS_ObjectSynchronizer_oops_do,
   SH_PS_FlatProfiler_oops_do,
   SH_PS_Management_oops_do,
   SH_PS_SystemDictionary_oops_do,
   SH_PS_jvmti_oops_do,
-  SH_PS_StringTable_oops_do,
   SH_PS_CodeCache_oops_do,
   // Leave this one last.
   SH_PS_NumElements
 };
 

@@ -133,10 +132,12 @@
 SharedHeap::StrongRootsScope::StrongRootsScope(SharedHeap* outer, bool activate)
   : MarkScope(activate)
 {
   if (_active) {
     outer->change_strong_roots_parity();
+    // Zero the claimed high water mark in the StringTable
+    StringTable::clear_parallel_claimed_index();
   }
 }
 
 SharedHeap::StrongRootsScope::~StrongRootsScope() {
   // nothing particular

@@ -161,16 +162,18 @@
     perm_gen()->ref_processor()->weak_oops_do(roots);
   }
   // Global (strong) JNI handles
   if (!_process_strong_tasks->is_task_claimed(SH_PS_JNIHandles_oops_do))
     JNIHandles::oops_do(roots);
+
   // All threads execute this; the individual threads are task groups.
-  if (ParallelGCThreads > 0) {
+  if (CollectedHeap::use_parallel_gc_threads()) {
     Threads::possibly_parallel_oops_do(roots, code_roots);
   } else {
     Threads::oops_do(roots, code_roots);
   }
+
   if (!_process_strong_tasks-> is_task_claimed(SH_PS_ObjectSynchronizer_oops_do))
     ObjectSynchronizer::oops_do(roots);
   if (!_process_strong_tasks->is_task_claimed(SH_PS_FlatProfiler_oops_do))
     FlatProfiler::oops_do(roots);
   if (!_process_strong_tasks->is_task_claimed(SH_PS_Management_oops_do))

@@ -184,16 +187,24 @@
     } else if (so & SO_SystemClasses) {
       SystemDictionary::always_strong_oops_do(roots);
     }
   }
 
-  if (!_process_strong_tasks->is_task_claimed(SH_PS_StringTable_oops_do)) {
+  // All threads execute the following. A specific chunk of buckets
+  // from the StringTable are the individual tasks.
     if (so & SO_Strings || (!collecting_perm_gen && !JavaObjectsInPerm)) {
+    if (CollectedHeap::use_parallel_gc_threads()) {
+      StringTable::possibly_parallel_oops_do(roots);
+    } else {
       StringTable::oops_do(roots);
     }
+  }
     if (JavaObjectsInPerm) {
       // Verify the string table contents are in the perm gen
+    if (CollectedHeap::use_parallel_gc_threads()) {
+      NOT_PRODUCT(StringTable::possibly_parallel_oops_do(&assert_is_perm_closure));
+    } else {
       NOT_PRODUCT(StringTable::oops_do(&assert_is_perm_closure));
     }
   }
 
   if (!_process_strong_tasks->is_task_claimed(SH_PS_CodeCache_oops_do)) {