6711316: Open source the Garbage-First garbage collector

First mercurial integration of the code for the Garbage-First garbage collector.

Reviewed-by: apetrusenko, iveresov, jmasa, sgoldman, tonyp, ysr

hotspot/src/share/vm/gc_implementation/shared/gcOverheadReporter.hpp

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+/*
+ * Copyright 2001-2007 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+// Keeps track of the GC overhead (both concurrent and STW). It stores
+// it in a large array and then prints it to tty at the end of the
+// execution.
+
+// See coTracker.hpp for the explanation on what groups are.
+
+// Let's set a maximum number of concurrent overhead groups, to
+// statically allocate any arrays we need and not to have to
+// malloc/free them. This is just a bit more convenient.
+enum {
+  MaxGCOverheadGroupNum = 4
+};
+
+typedef struct {
+  double _start_sec;
+  double _end_sec;
+
+  double _conc_overhead[MaxGCOverheadGroupNum];
+  double _stw_overhead;
+} GCOverheadReporterEntry;
+
+class GCOverheadReporter {
+  friend class COReportingThread;
+
+private:
+  enum PrivateConstants {
+    DefaultReporterLength = 128 * 1024
+  };
+
+  // Reference to the single instance of this class.
+  static GCOverheadReporter* _reporter;
+
+  // These three references point to the array that contains the GC
+  // overhead entries (_base is the base of the array, _top is the
+  // address passed the last entry of the array, _curr is the next
+  // entry to be used).
+  GCOverheadReporterEntry* _base;
+  GCOverheadReporterEntry* _top;
+  GCOverheadReporterEntry* _curr;
+
+  // The number of concurrent overhead groups.
+  size_t _group_num;
+
+  // The wall-clock time of the end of the last recorded period of GC
+  // overhead.
+  double _prev_end_sec;
+
+  // Names for the concurrent overhead groups.
+  const char* _group_names[MaxGCOverheadGroupNum];
+
+  // Add a new entry to the large array. conc_overhead being NULL is
+  // equivalent to an array full of 0.0s. conc_overhead should have a
+  // length of at least _group_num.
+  void add(double start_sec, double end_sec,
+           double* conc_overhead,
+           double stw_overhead);
+
+  // Add an entry that represents concurrent GC overhead.
+  // conc_overhead must be at least of length _group_num.
+  // conc_overhead being NULL is equivalent to an array full of 0.0s.
+  void add_conc_overhead(double start_sec, double end_sec,
+                         double* conc_overhead) {
+    add(start_sec, end_sec, conc_overhead, 0.0);
+  }
+
+  // Add an entry that represents STW GC overhead.
+  void add_stw_overhead(double start_sec, double end_sec,
+                        double stw_overhead) {
+    add(start_sec, end_sec, NULL, stw_overhead);
+  }
+
+  // It records the start of a STW pause (i.e. it records the
+  // concurrent overhead up to that point)
+  void record_stw_start(double start_sec);
+
+  // It records the end of a STW pause (i.e. it records the overhead
+  // associated with the pause and adjusts all the trackers to reflect
+  // the pause)
+  void record_stw_end(double end_sec);
+
+  // It queries all the trackers of their concurrent overhead and
+  // records it.
+  void collect_and_record_conc_overhead(double end_sec);
+
+  // It prints the contents of the GC overhead array
+  void print() const;
+
+
+  // Constructor. The same preconditions for group_num and group_names
+  // from initGCOverheadReporter apply here too.
+  GCOverheadReporter(size_t group_num,
+                     const char* group_names[],
+                     size_t length = DefaultReporterLength);
+
+public:
+
+  // statics
+
+  // It initialises the GCOverheadReporter and launches the concurrent
+  // overhead reporting thread. Both actions happen only if the
+  // GCOverheadReporting parameter is set. The length of the
+  // group_names array should be >= group_num and group_num should be
+  // <= MaxGCOverheadGroupNum. Entries group_namnes[0..group_num-1]
+  // should not be NULL.
+  static void initGCOverheadReporter(size_t group_num,
+                                     const char* group_names[]);
+
+  // The following three are provided for convenience and they are
+  // wrappers around record_stw_start(start_sec), record_stw_end(end_sec),
+  // and print(). Each of these checks whether GC overhead reporting
+  // is on (i.e. _reporter != NULL) and, if it is, calls the
+  // corresponding method. Saves from repeating this pattern again and
+  // again from the places where they need to be called.
+  static void recordSTWStart(double start_sec);
+  static void recordSTWEnd(double end_sec);
+  static void printGCOverhead();
+};