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hotspot/src/share/vm/runtime/perfMemory.hpp

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+/*
+ * Copyright 2001-2006 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.
+ *
+ */
+
+/*
+ * PerfData Version Constants
+ *   - Major Version - change whenever the structure of PerfDataEntry changes
+ *   - Minor Version - change whenever the data within the PerfDataEntry
+ *                     structure changes. for example, new unit or variability
+ *                     values are added or new PerfData subtypes are added.
+ */
+#define PERFDATA_MAJOR_VERSION 2
+#define PERFDATA_MINOR_VERSION 0
+
+/* Byte order of the PerfData memory region. The byte order is exposed in
+ * the PerfData memory region as the data in the memory region may have
+ * been generated by a little endian JVM implementation. Tracking the byte
+ * order in the PerfData memory region allows Java applications to adapt
+ * to the native byte order for monitoring purposes. This indicator is
+ * also useful when a snapshot of the PerfData memory region is shipped
+ * to a machine with a native byte order different from that of the
+ * originating machine.
+ */
+#define PERFDATA_BIG_ENDIAN     0
+#define PERFDATA_LITTLE_ENDIAN  1
+
+/*
+ * The PerfDataPrologue structure is known by the PerfDataBuffer Java class
+ * libraries that read the PerfData memory region. The size and the position
+ * of the fields must be changed along with their counterparts in the
+ * PerfDataBuffer Java class. The first four bytes of this structure
+ * should never change, or compatibility problems between the monitoring
+ * applications and Hotspot VMs will result. The reserved fields are
+ * available for future enhancements.
+ */
+typedef struct {
+  jint   magic;              // magic number - 0xcafec0c0
+  jbyte  byte_order;         // byte order of the buffer
+  jbyte  major_version;      // major and minor version numbers
+  jbyte  minor_version;
+  jbyte  accessible;         // ready to access
+  jint   used;               // number of PerfData memory bytes used
+  jint   overflow;           // number of bytes of overflow
+  jlong  mod_time_stamp;     // time stamp of last structural modification
+  jint   entry_offset;       // offset of the first PerfDataEntry
+  jint   num_entries;        // number of allocated PerfData entries
+} PerfDataPrologue;
+
+/* The PerfDataEntry structure defines the fixed portion of an entry
+ * in the PerfData memory region. The PerfDataBuffer Java libraries
+ * are aware of this structure and need to be changed when this
+ * structure changes.
+ */
+typedef struct {
+
+  jint entry_length;      // entry length in bytes
+  jint name_offset;       // offset of the data item name
+  jint vector_length;     // length of the vector. If 0, then scalar
+  jbyte data_type;        // type of the data item -
+                          // 'B','Z','J','I','S','C','D','F','V','L','['
+  jbyte flags;            // flags indicating misc attributes
+  jbyte data_units;       // unit of measure for the data type
+  jbyte data_variability; // variability classification of data type
+  jint  data_offset;      // offset of the data item
+
+/*
+  body of PerfData memory entry is variable length
+
+  jbyte[name_length] data_name;        // name of the data item
+  jbyte[pad_length] data_pad;          // alignment of data item
+  j<data_type>[data_length] data_item; // array of appropriate types.
+                                       // data_length is > 1 only when the
+                                       // data_type is T_ARRAY.
+*/
+} PerfDataEntry;
+
+// Prefix of performance data file.
+static const char PERFDATA_NAME[] = "hsperfdata";
+
+// UINT_CHARS contains the number of characters holding a process id
+// (i.e. pid). pid is defined as unsigned "int" so the maximum possible pid value
+// would be 2^32 - 1 (4294967295) which can be represented as a 10 characters
+// string.
+static const size_t UINT_CHARS = 10;
+
+// Add 1 for the '_' character between PERFDATA_NAME and pid. The '\0' terminating
+// character will be included in the sizeof(PERFDATA_NAME) operation.
+static const size_t PERFDATA_FILENAME_LEN = sizeof(PERFDATA_NAME) +
+                                            UINT_CHARS + 1;
+
+/* the PerfMemory class manages creation, destruction,
+ * and allocation of the PerfData region.
+ */
+class PerfMemory : AllStatic {
+    friend class VMStructs;
+  private:
+    static char*  _start;
+    static char*  _end;
+    static char*  _top;
+    static size_t _capacity;
+    static PerfDataPrologue*  _prologue;
+    static jint   _initialized;
+
+    static void create_memory_region(size_t sizep);
+    static void delete_memory_region();
+
+  public:
+    enum PerfMemoryMode {
+      PERF_MODE_RO = 0,
+      PERF_MODE_RW = 1
+    };
+
+    static char* alloc(size_t size);
+    static char* start() { return _start; }
+    static char* end() { return _end; }
+    static size_t used() { return (size_t) (_top - _start); }
+    static size_t capacity() { return _capacity; }
+    static bool is_initialized() { return _initialized != 0; }
+    static bool contains(char* addr) {
+      return ((_start != NULL) && (addr >= _start) && (addr < _end));
+    }
+    static void mark_updated();
+
+    // methods for attaching to and detaching from the PerfData
+    // memory segment of another JVM process on the same system.
+    static void attach(const char* user, int vmid, PerfMemoryMode mode,
+                       char** addrp, size_t* size, TRAPS);
+    static void detach(char* addr, size_t bytes, TRAPS);
+
+    static void initialize();
+    static void destroy();
+    static void set_accessible(bool value) {
+      if (UsePerfData) {
+        _prologue->accessible = value;
+      }
+    }
+
+    // filename of backing store or NULL if none.
+    static char* backing_store_filename();
+
+    // returns the complete file path of hsperfdata.
+    // the caller is expected to free the allocated memory.
+    static char* get_perfdata_file_path();
+};
+
+void perfMemory_init();
+void perfMemory_exit();