diff hotspot/src/share/vm/gc/g1/g1ConcurrentMarkObjArrayProcessor.hpp @ 42597:a9611bab7578

8057003: Large reference arrays cause extremely long synchronization times Summary: Slice large object arrays into parts so that the synchronization of marking threads with an STW pause request does not take long. Reviewed-by: ehelin, pliden
author tschatzl
date Thu, 24 Nov 2016 11:27:57 +0100
parents
children 6061df52d610
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--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc/g1/g1ConcurrentMarkObjArrayProcessor.hpp	Thu Nov 24 11:27:57 2016 +0100
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+/*
+ * Copyright (c) 2016, 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.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_GC_G1_G1CONCURRENTMARKOBJARRAYPROCESSOR_HPP
+#define SHARE_VM_GC_G1_G1CONCURRENTMARKOBJARRAYPROCESSOR_HPP
+
+#include "oops/oopsHierarchy.hpp"
+#include "memory/allocation.hpp"
+
+class G1CMTask;
+
+// Helper class to mark through large objArrays during marking in an efficient way.
+// Instead of pushing large object arrays, we push continuations onto the
+// mark stack. These continuations are identified by having their LSB set.
+// This allows incremental processing of large objects.
+class G1CMObjArrayProcessor VALUE_OBJ_CLASS_SPEC {
+private:
+  // The bit mask for the continuation indicator of elements on the mark stack.
+  static const size_t ArraySliceBit = 1;
+
+  // Reference to the task for doing the actual work.
+  G1CMTask* _task;
+
+  // Encodes the given address as a continuation "oop".
+  oop encode_array_slice(HeapWord* addr);
+  // Remove the continuation marker from the given oop from the mark stack.
+  HeapWord* decode_array_slice(oop value);
+
+  // Push the continuation at the given address onto the mark stack.
+  void push_array_slice(HeapWord* addr);
+
+  // Process (apply the closure) on the given continuation of the given objArray.
+  size_t process_array_slice(objArrayOop const obj, HeapWord* start_from, size_t remaining);
+public:
+  static bool is_array_slice(void* obj) { return ((uintptr_t)obj & ArraySliceBit) != 0; }
+
+  static bool should_be_sliced(oop obj);
+
+  G1CMObjArrayProcessor(G1CMTask* task) : _task(task) {
+  }
+
+  // Process the given continuation "oop". Returns the number of words scanned.
+  size_t process_slice(oop obj);
+  // Start processing the given objArrayOop by scanning the header and pushing its
+  // continuation.
+  size_t process_obj(oop obj);
+};
+
+#endif /* SHARE_VM_GC_G1_G1CONCURRENTMARKOBJARRAYPROCESSOR_HPP */