view src/share/vm/gc_implementation/g1/concurrentG1RefineThread.cpp @ 2684:4f41766176cf

7084509: G1: fix inconsistencies and mistakes in the young list target length calculations Summary: Fixed inconsistencies and mistakes in the young list target length calculations so that a) the calculated target length is optimal (before, it was not), b) other parameters like max survivor size and max gc locker eden expansion are always consistent with the calculated target length (before, they were not always), and c) the resulting target length was always bound by desired min and max values (before, it was not). Reviewed-by: brutisso, johnc
author tonyp
date Thu, 08 Sep 2011 05:16:49 -0400
parents f95d63e2154a
children
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/*
 * Copyright (c) 2001, 2010, 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 "gc_implementation/g1/concurrentG1Refine.hpp"
#include "gc_implementation/g1/concurrentG1RefineThread.hpp"
#include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
#include "gc_implementation/g1/g1CollectorPolicy.hpp"
#include "memory/resourceArea.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/mutexLocker.hpp"

ConcurrentG1RefineThread::
ConcurrentG1RefineThread(ConcurrentG1Refine* cg1r, ConcurrentG1RefineThread *next,
                         int worker_id_offset, int worker_id) :
  ConcurrentGCThread(),
  _worker_id_offset(worker_id_offset),
  _worker_id(worker_id),
  _active(false),
  _next(next),
  _monitor(NULL),
  _cg1r(cg1r),
  _vtime_accum(0.0)
{

  // Each thread has its own monitor. The i-th thread is responsible for signalling
  // to thread i+1 if the number of buffers in the queue exceeds a threashold for this
  // thread. Monitors are also used to wake up the threads during termination.
  // The 0th worker in notified by mutator threads and has a special monitor.
  // The last worker is used for young gen rset size sampling.
  if (worker_id > 0) {
    _monitor = new Monitor(Mutex::nonleaf, "Refinement monitor", true);
  } else {
    _monitor = DirtyCardQ_CBL_mon;
  }
  initialize();
  create_and_start();
}

void ConcurrentG1RefineThread::initialize() {
  if (_worker_id < cg1r()->worker_thread_num()) {
    // Current thread activation threshold
    _threshold = MIN2<int>(cg1r()->thread_threshold_step() * (_worker_id + 1) + cg1r()->green_zone(),
                           cg1r()->yellow_zone());
    // A thread deactivates once the number of buffer reached a deactivation threshold
    _deactivation_threshold = MAX2<int>(_threshold - cg1r()->thread_threshold_step(), cg1r()->green_zone());
  } else {
    set_active(true);
  }
}

void ConcurrentG1RefineThread::sample_young_list_rs_lengths() {
  G1CollectedHeap* g1h = G1CollectedHeap::heap();
  G1CollectorPolicy* g1p = g1h->g1_policy();
  if (g1p->adaptive_young_list_length()) {
    int regions_visited = 0;
    g1h->young_list()->rs_length_sampling_init();
    while (g1h->young_list()->rs_length_sampling_more()) {
      g1h->young_list()->rs_length_sampling_next();
      ++regions_visited;

      // we try to yield every time we visit 10 regions
      if (regions_visited == 10) {
        if (_sts.should_yield()) {
          _sts.yield("G1 refine");
          // we just abandon the iteration
          break;
        }
        regions_visited = 0;
      }
    }

    g1p->revise_young_list_target_length_if_necessary();
  }
}

void ConcurrentG1RefineThread::run_young_rs_sampling() {
  DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
  _vtime_start = os::elapsedVTime();
  while(!_should_terminate) {
    _sts.join();
    sample_young_list_rs_lengths();
    _sts.leave();

    if (os::supports_vtime()) {
      _vtime_accum = (os::elapsedVTime() - _vtime_start);
    } else {
      _vtime_accum = 0.0;
    }

    MutexLockerEx x(_monitor, Mutex::_no_safepoint_check_flag);
    if (_should_terminate) {
      break;
    }
    _monitor->wait(Mutex::_no_safepoint_check_flag, G1ConcRefinementServiceIntervalMillis);
  }
}

void ConcurrentG1RefineThread::wait_for_completed_buffers() {
  DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
  MutexLockerEx x(_monitor, Mutex::_no_safepoint_check_flag);
  while (!_should_terminate && !is_active()) {
    _monitor->wait(Mutex::_no_safepoint_check_flag);
  }
}

bool ConcurrentG1RefineThread::is_active() {
  DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
  return _worker_id > 0 ? _active : dcqs.process_completed_buffers();
}

void ConcurrentG1RefineThread::activate() {
  MutexLockerEx x(_monitor, Mutex::_no_safepoint_check_flag);
  if (_worker_id > 0) {
    if (G1TraceConcRefinement) {
      DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
      gclog_or_tty->print_cr("G1-Refine-activated worker %d, on threshold %d, current %d",
                             _worker_id, _threshold, (int)dcqs.completed_buffers_num());
    }
    set_active(true);
  } else {
    DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
    dcqs.set_process_completed(true);
  }
  _monitor->notify();
}

void ConcurrentG1RefineThread::deactivate() {
  MutexLockerEx x(_monitor, Mutex::_no_safepoint_check_flag);
  if (_worker_id > 0) {
    if (G1TraceConcRefinement) {
      DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
      gclog_or_tty->print_cr("G1-Refine-deactivated worker %d, off threshold %d, current %d",
                             _worker_id, _deactivation_threshold, (int)dcqs.completed_buffers_num());
    }
    set_active(false);
  } else {
    DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
    dcqs.set_process_completed(false);
  }
}

void ConcurrentG1RefineThread::run() {
  initialize_in_thread();
  wait_for_universe_init();

  if (_worker_id >= cg1r()->worker_thread_num()) {
    run_young_rs_sampling();
    terminate();
    return;
  }

  _vtime_start = os::elapsedVTime();
  while (!_should_terminate) {
    DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();

    // Wait for work
    wait_for_completed_buffers();

    if (_should_terminate) {
      break;
    }

    _sts.join();

    do {
      int curr_buffer_num = (int)dcqs.completed_buffers_num();
      // If the number of the buffers falls down into the yellow zone,
      // that means that the transition period after the evacuation pause has ended.
      if (dcqs.completed_queue_padding() > 0 && curr_buffer_num <= cg1r()->yellow_zone()) {
        dcqs.set_completed_queue_padding(0);
      }

      if (_worker_id > 0 && curr_buffer_num <= _deactivation_threshold) {
        // If the number of the buffer has fallen below our threshold
        // we should deactivate. The predecessor will reactivate this
        // thread should the number of the buffers cross the threshold again.
        deactivate();
        break;
      }

      // Check if we need to activate the next thread.
      if (_next != NULL && !_next->is_active() && curr_buffer_num > _next->_threshold) {
        _next->activate();
      }
    } while (dcqs.apply_closure_to_completed_buffer(_worker_id + _worker_id_offset, cg1r()->green_zone()));

    // We can exit the loop above while being active if there was a yield request.
    if (is_active()) {
      deactivate();
    }

    _sts.leave();

    if (os::supports_vtime()) {
      _vtime_accum = (os::elapsedVTime() - _vtime_start);
    } else {
      _vtime_accum = 0.0;
    }
  }
  assert(_should_terminate, "just checking");
  terminate();
}


void ConcurrentG1RefineThread::yield() {
  if (G1TraceConcRefinement) {
    gclog_or_tty->print_cr("G1-Refine-yield");
  }
  _sts.yield("G1 refine");
  if (G1TraceConcRefinement) {
    gclog_or_tty->print_cr("G1-Refine-yield-end");
  }
}

void ConcurrentG1RefineThread::stop() {
  // it is ok to take late safepoints here, if needed
  {
    MutexLockerEx mu(Terminator_lock);
    _should_terminate = true;
  }

  {
    MutexLockerEx x(_monitor, Mutex::_no_safepoint_check_flag);
    _monitor->notify();
  }

  {
    MutexLockerEx mu(Terminator_lock);
    while (!_has_terminated) {
      Terminator_lock->wait();
    }
  }
  if (G1TraceConcRefinement) {
    gclog_or_tty->print_cr("G1-Refine-stop");
  }
}

void ConcurrentG1RefineThread::print() const {
  print_on(tty);
}

void ConcurrentG1RefineThread::print_on(outputStream* st) const {
  st->print("\"G1 Concurrent Refinement Thread#%d\" ", _worker_id);
  Thread::print_on(st);
  st->cr();
}