JDK14/Java14源码在线阅读

/*
 * Copyright (c) 2003, 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
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 * questions.
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#include "precompiled.hpp"
#include "classfile/systemDictionary.hpp"
#include "classfile/vmSymbols.hpp"
#include "memory/allocation.inline.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/atomic.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/javaCalls.hpp"
#include "services/lowMemoryDetector.hpp"
#include "services/management.hpp"
#include "services/memoryManager.hpp"
#include "services/memoryPool.hpp"
#include "services/memoryService.hpp"
#include "services/gcNotifier.hpp"
#include "utilities/dtrace.hpp"

MemoryManager::MemoryManager(const char* name) : _name(name) {
  _num_pools = 0;
  (void)const_cast<instanceOop&>(_memory_mgr_obj = instanceOop(NULL));
}

int MemoryManager::add_pool(MemoryPool* pool) {
  int index = _num_pools;
  assert(index < MemoryManager::max_num_pools, "_num_pools exceeds the max");
  if (index < MemoryManager::max_num_pools) {
    _pools[index] = pool;
    _num_pools++;
  }
  pool->add_manager(this);
  return index;
}

MemoryManager* MemoryManager::get_code_cache_memory_manager() {
  return new MemoryManager("CodeCacheManager");
}

MemoryManager* MemoryManager::get_metaspace_memory_manager() {
  return new MemoryManager("Metaspace Manager");
}

instanceOop MemoryManager::get_memory_manager_instance(TRAPS) {
  // Must do an acquire so as to force ordering of subsequent
  // loads from anything _memory_mgr_obj points to or implies.
  instanceOop mgr_obj = Atomic::load_acquire(&_memory_mgr_obj);
  if (mgr_obj == NULL) {
    // It's ok for more than one thread to execute the code up to the locked region.
    // Extra manager instances will just be gc'ed.
    Klass* k = Management::sun_management_ManagementFactoryHelper_klass(CHECK_0);

    Handle mgr_name = java_lang_String::create_from_str(name(), CHECK_0);

    JavaValue result(T_OBJECT);
    JavaCallArguments args;
    args.push_oop(mgr_name);    // Argument 1

    Symbol* method_name = NULL;
    Symbol* signature = NULL;
    if (is_gc_memory_manager()) {
      Klass* extKlass = Management::com_sun_management_internal_GarbageCollectorExtImpl_klass(CHECK_0);
      // com.sun.management.GarbageCollectorMXBean is in jdk.management module which may not be present.
      if (extKlass != NULL) {
        k = extKlass;
      }

      method_name = vmSymbols::createGarbageCollector_name();

      signature = vmSymbols::createGarbageCollector_signature();
      args.push_oop(Handle());      // Argument 2 (for future extension)
    } else {
      method_name = vmSymbols::createMemoryManager_name();
      signature = vmSymbols::createMemoryManager_signature();
    }

    InstanceKlass* ik = InstanceKlass::cast(k);

    JavaCalls::call_static(&result,
                           ik,
                           method_name,
                           signature,
                           &args,
                           CHECK_0);

    instanceOop m = (instanceOop) result.get_jobject();
    instanceHandle mgr(THREAD, m);

    {
      // Get lock before setting _memory_mgr_obj
      // since another thread may have created the instance
      MutexLocker ml(Management_lock);

      // Check if another thread has created the management object.  We reload
      // _memory_mgr_obj here because some other thread may have initialized
      // it while we were executing the code before the lock.
      //
      // The lock has done an acquire, so the load can't float above it, but
      // we need to do a load_acquire as above.
      mgr_obj = Atomic::load_acquire(&_memory_mgr_obj);
      if (mgr_obj != NULL) {
         return mgr_obj;
      }

      // Get the address of the object we created via call_special.
      mgr_obj = mgr();

      // Use store barrier to make sure the memory accesses associated
      // with creating the management object are visible before publishing
      // its address.  The unlock will publish the store to _memory_mgr_obj
      // because it does a release first.
      Atomic::release_store(&_memory_mgr_obj, mgr_obj);
    }
  }

  return mgr_obj;
}

void MemoryManager::oops_do(OopClosure* f) {
  f->do_oop((oop*) &_memory_mgr_obj);
}

GCStatInfo::GCStatInfo(int num_pools) {
  // initialize the arrays for memory usage
  _before_gc_usage_array = NEW_C_HEAP_ARRAY(MemoryUsage, num_pools, mtInternal);
  _after_gc_usage_array  = NEW_C_HEAP_ARRAY(MemoryUsage, num_pools, mtInternal);
  _usage_array_size = num_pools;
  clear();
}

GCStatInfo::~GCStatInfo() {
  FREE_C_HEAP_ARRAY(MemoryUsage*, _before_gc_usage_array);
  FREE_C_HEAP_ARRAY(MemoryUsage*, _after_gc_usage_array);
}

void GCStatInfo::set_gc_usage(int pool_index, MemoryUsage usage, bool before_gc) {
  MemoryUsage* gc_usage_array;
  if (before_gc) {
    gc_usage_array = _before_gc_usage_array;
  } else {
    gc_usage_array = _after_gc_usage_array;
  }
  gc_usage_array[pool_index] = usage;
}

void GCStatInfo::clear() {
  _index = 0;
  _start_time = 0L;
  _end_time = 0L;
  for (int i = 0; i < _usage_array_size; i++) ::new (&_before_gc_usage_array[i]) MemoryUsage();
  for (int i = 0; i < _usage_array_size; i++) ::new (&_after_gc_usage_array[i]) MemoryUsage();
}


GCMemoryManager::GCMemoryManager(const char* name, const char* gc_end_message) :
  MemoryManager(name), _gc_end_message(gc_end_message) {
  _num_collections = 0;
  _last_gc_stat = NULL;
  _last_gc_lock = new Mutex(Mutex::leaf, "_last_gc_lock", true,
                            Mutex::_safepoint_check_never);
  _current_gc_stat = NULL;
  _num_gc_threads = 1;
  _notification_enabled = false;
}

GCMemoryManager::~GCMemoryManager() {
  delete _last_gc_stat;
  delete _last_gc_lock;
  delete _current_gc_stat;
}

void GCMemoryManager::add_pool(MemoryPool* pool) {
  add_pool(pool, true);
}

void GCMemoryManager::add_pool(MemoryPool* pool, bool always_affected_by_gc) {
  int index = MemoryManager::add_pool(pool);
  _pool_always_affected_by_gc[index] = always_affected_by_gc;
}

void GCMemoryManager::initialize_gc_stat_info() {
  assert(MemoryService::num_memory_pools() > 0, "should have one or more memory pools");
  _last_gc_stat = new(ResourceObj::C_HEAP, mtGC) GCStatInfo(MemoryService::num_memory_pools());
  _current_gc_stat = new(ResourceObj::C_HEAP, mtGC) GCStatInfo(MemoryService::num_memory_pools());
  // tracking concurrent collections we need two objects: one to update, and one to
  // hold the publicly available "last (completed) gc" information.
}

void GCMemoryManager::gc_begin(bool recordGCBeginTime, bool recordPreGCUsage,
                               bool recordAccumulatedGCTime) {
  assert(_last_gc_stat != NULL && _current_gc_stat != NULL, "Just checking");
  if (recordAccumulatedGCTime) {
    _accumulated_timer.start();
  }
  // _num_collections now increases in gc_end, to count completed collections
  if (recordGCBeginTime) {
    _current_gc_stat->set_index(_num_collections+1);
    _current_gc_stat->set_start_time(Management::timestamp());
  }

  if (recordPreGCUsage) {
    // Keep memory usage of all memory pools
    for (int i = 0; i < MemoryService::num_memory_pools(); i++) {
      MemoryPool* pool = MemoryService::get_memory_pool(i);
      MemoryUsage usage = pool->get_memory_usage();
      _current_gc_stat->set_before_gc_usage(i, usage);
      HOTSPOT_MEM_POOL_GC_BEGIN(
        (char *) name(), strlen(name()),
        (char *) pool->name(), strlen(pool->name()),
        usage.init_size(), usage.used(),
        usage.committed(), usage.max_size());
    }
  }
}

// A collector MUST, even if it does not complete for some reason,
// make a TraceMemoryManagerStats object where countCollection is true,
// to ensure the current gc stat is placed in _last_gc_stat.
void GCMemoryManager::gc_end(bool recordPostGCUsage,
                             bool recordAccumulatedGCTime,
                             bool recordGCEndTime, bool countCollection,
                             GCCause::Cause cause,
                             bool allMemoryPoolsAffected) {
  if (recordAccumulatedGCTime) {
    _accumulated_timer.stop();
  }
  if (recordGCEndTime) {
    _current_gc_stat->set_end_time(Management::timestamp());
  }

  if (recordPostGCUsage) {
    int i;
    // keep the last gc statistics for all memory pools
    for (i = 0; i < MemoryService::num_memory_pools(); i++) {
      MemoryPool* pool = MemoryService::get_memory_pool(i);
      MemoryUsage usage = pool->get_memory_usage();

      HOTSPOT_MEM_POOL_GC_END(
        (char *) name(), strlen(name()),
        (char *) pool->name(), strlen(pool->name()),
        usage.init_size(), usage.used(),
        usage.committed(), usage.max_size());

      _current_gc_stat->set_after_gc_usage(i, usage);
    }

    // Set last collection usage of the memory pools managed by this collector
    for (i = 0; i < num_memory_pools(); i++) {
      MemoryPool* pool = get_memory_pool(i);
      MemoryUsage usage = pool->get_memory_usage();

      if (allMemoryPoolsAffected || pool_always_affected_by_gc(i)) {
        // Compare with GC usage threshold
        pool->set_last_collection_usage(usage);
        LowMemoryDetector::detect_after_gc_memory(pool);
      }
    }
  }

  if (countCollection) {
    _num_collections++;

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