JDK14/Java14源码在线阅读

/*
 * Copyright (c) 2001, 2019, 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.
 *
 */

#include "precompiled.hpp"
#include "classfile/systemDictionary.hpp"
#include "classfile/vmSymbols.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/resourceArea.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/arguments.hpp"
#include "runtime/java.hpp"
#include "runtime/javaCalls.hpp"
#include "runtime/os.hpp"
#include "runtime/perfData.inline.hpp"
#include "runtime/statSampler.hpp"
#include "runtime/vm_version.hpp"

// --------------------------------------------------------
// StatSamplerTask

class StatSamplerTask : public PeriodicTask {
  public:
    StatSamplerTask(int interval_time) : PeriodicTask(interval_time) {}
    void task() { StatSampler::collect_sample(); }
};


//----------------------------------------------------------
// Implementation of StatSampler

StatSamplerTask*              StatSampler::_task   = NULL;
PerfDataList*                 StatSampler::_sampled = NULL;

/*
 * the initialize method is called from the engage() method
 * and is responsible for initializing various global variables.
 */
void StatSampler::initialize() {

  if (!UsePerfData) return;

  // create performance data that could not be created prior
  // to vm_init_globals() or otherwise have no logical home.

  create_misc_perfdata();

  // get copy of the sampled list
  _sampled = PerfDataManager::sampled();

}

/*
 * The engage() method is called at initialization time via
 * Thread::create_vm() to initialize the StatSampler and
 * register it with the WatcherThread as a periodic task.
 */
void StatSampler::engage() {

  if (!UsePerfData) return;

  if (!is_active()) {

    initialize();

    // start up the periodic task
    _task = new StatSamplerTask(PerfDataSamplingInterval);
    _task->enroll();
  }
}


/*
 * the disengage() method is responsible for deactivating the periodic
 * task and, if logging was enabled, for logging the final sample. This
 * method is called from before_exit() in java.cpp and is only called
 * after the WatcherThread has been stopped.
 */
void StatSampler::disengage() {

  if (!UsePerfData) return;

  if (!is_active())
    return;

  // remove StatSamplerTask
  _task->disenroll();
  delete _task;
  _task = NULL;

  // force a final sample
  sample_data(_sampled);
}

/*
 * the destroy method is responsible for releasing any resources used by
 * the StatSampler prior to shutdown of the VM. this method is called from
 * before_exit() in java.cpp and is only called after the WatcherThread
 * has stopped.
 */
void StatSampler::destroy() {

  if (!UsePerfData) return;

  if (_sampled != NULL) {
    delete(_sampled);
    _sampled = NULL;
  }
}

/*
 * The sample_data() method is responsible for sampling the
 * the data value for each PerfData instance in the given list.
 */
void StatSampler::sample_data(PerfDataList* list) {

  assert(list != NULL, "null list unexpected");

  for (int index = 0; index < list->length(); index++) {
    PerfData* item = list->at(index);
    item->sample();
  }
}

/*
 * the collect_sample() method is the method invoked by the
 * WatcherThread via the PeriodicTask::task() method. This method
 * is responsible for collecting data samples from sampled
 * PerfData instances every PerfDataSamplingInterval milliseconds.
 * It is also responsible for logging the requested set of
 * PerfData instances every _sample_count milliseconds. While
 * logging data, it will output a column header after every _print_header
 * rows of data have been logged.
 */
void StatSampler::collect_sample() {

  // future - check for new PerfData objects. PerfData objects might
  // get added to the PerfDataManager lists after we have already
  // built our local copies.
  //
  // if (PerfDataManager::count() > previous) {
  //   // get a new copy of the sampled list
  //   if (_sampled != NULL) {
  //     delete(_sampled);
  //     _sampled = NULL;
  //   }
  //   _sampled = PerfDataManager::sampled();
  // }

  assert(_sampled != NULL, "list not initialized");

  sample_data(_sampled);
}

/*
 * method to upcall into Java to return the value of the specified
 * property as a utf8 string, or NULL if does not exist. The caller
 * is responsible for setting a ResourceMark for proper cleanup of
 * the utf8 strings.
 */
const char* StatSampler::get_system_property(const char* name, TRAPS) {

  // setup the arguments to getProperty
  Handle key_str   = java_lang_String::create_from_str(name, CHECK_NULL);

  // return value
  JavaValue result(T_OBJECT);

  // public static String getProperty(String key, String def);
  JavaCalls::call_static(&result,
                         SystemDictionary::System_klass(),
                         vmSymbols::getProperty_name(),
                         vmSymbols::string_string_signature(),
                         key_str,
                         CHECK_NULL);

  oop value_oop = (oop)result.get_jobject();
  if (value_oop == NULL) {
    return NULL;
  }

  // convert Java String to utf8 string
  char* value = java_lang_String::as_utf8_string(value_oop);

  return value;
}

/*
 * The list of System Properties that have corresponding PerfData
 * string instrumentation created by retrieving the named property's
 * value from System.getProperty() and unconditionally creating a
 * PerfStringConstant object initialized to the retrieved value. This
 * is not an exhaustive list of Java properties with corresponding string
 * instrumentation as the create_system_property_instrumentation() method
 * creates other property based instrumentation conditionally.
 */

// stable interface, supported counters
static const char* property_counters_ss[] = {
  "java.vm.specification.version",
  "java.vm.specification.name",
  "java.vm.specification.vendor",
  "java.vm.version",
  "java.vm.name",
  "java.vm.vendor",
  "java.vm.info",
  "jdk.debug",
  "java.library.path",
  "java.class.path",
  "java.version",
  "java.home",
  NULL
};

// unstable interface, supported counters
static const char* property_counters_us[] = {
  NULL
};

// unstable interface, unsupported counters
static const char* property_counters_uu[] = {
  "sun.boot.library.path",
  NULL
};

typedef struct {
  const char** property_list;
  CounterNS name_space;
} PropertyCounters;

static PropertyCounters property_counters[] = {
  { property_counters_ss, JAVA_PROPERTY },
  { property_counters_us, COM_PROPERTY },
  { property_counters_uu, SUN_PROPERTY },
  { NULL, SUN_PROPERTY }
};


/*
 * Method to create PerfData string instruments that contain the values
 * of various system properties. String instruments are created for each
 * property specified in the property lists provided in property_counters[].
 * Property counters have a counter name space prefix prepended to the
 * property name as indicated in property_counters[].
 */
void StatSampler::create_system_property_instrumentation(TRAPS) {

  ResourceMark rm;

  for (int i = 0; property_counters[i].property_list != NULL; i++) {

    for (int j = 0; property_counters[i].property_list[j] != NULL; j++) {

      const char* property_name = property_counters[i].property_list[j];
      assert(property_name != NULL, "property name should not be NULL");

      const char* value = get_system_property(property_name, CHECK);

      // the property must exist
      assert(value != NULL, "property name should be valid");

      if (value != NULL) {
        // create the property counter
        PerfDataManager::create_string_constant(property_counters[i].name_space,
                                                property_name, value, CHECK);
      }
    }
  }
}

/*
 * The create_misc_perfdata() method provides a place to create
 * PerfData instances that would otherwise have no better place
 * to exist.
 */
void StatSampler::create_misc_perfdata() {

  ResourceMark rm;
  EXCEPTION_MARK;

  // numeric constants

  // frequency of the native high resolution timer
  PerfDataManager::create_constant(SUN_OS, "hrt.frequency",
                                   PerfData::U_Hertz, os::elapsed_frequency(),
                                   CHECK);

  // string constants

  // create string instrumentation for various Java properties.
  create_system_property_instrumentation(CHECK);

  // HotSpot flags (from .hotspotrc) and args (from command line)
  //
  PerfDataManager::create_string_constant(JAVA_RT, "vmFlags",
                                          Arguments::jvm_flags(), CHECK);
  PerfDataManager::create_string_constant(JAVA_RT, "vmArgs",
                                          Arguments::jvm_args(), CHECK);

  // java class name/jar file and arguments to main class
  // note: name is cooridnated with launcher and Arguments.cpp
  PerfDataManager::create_string_constant(SUN_RT, "javaCommand",
                                          Arguments::java_command(), CHECK);

  // the Java VM Internal version string

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