src/hotspot/share/gc/shared/workerManager.hpp

/*
 * Copyright (c) 2016, 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.
 *
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#ifndef SHARE_VM_GC_SHARED_WORKERMANAGER_HPP
#define SHARE_VM_GC_SHARED_WORKERMANAGER_HPP

#include "gc/shared/adaptiveSizePolicy.hpp"

class WorkerManager : public AllStatic {
 public:
  // Create additional workers as needed.
  //   active_workers - number of workers being requested for an upcoming
  // parallel task.
  //   total_workers - total number of workers.  This is the maximum
  // number possible.
  //   created_workers - number of workers already created.  This maybe
  // less than, equal to, or greater than active workers.  If greater than
  // or equal to active_workers, nothing is done.
  //   worker_type - type of thread.
  //   initializing - true if this is called to get the initial number of
  // GC workers.
  // If initializing is true, do a vm exit if the workers cannot be created.
  // The initializing = true case is for JVM start up and failing to
  // create all the worker at start should considered a problem so exit.
  // If initializing = false, there are already some number of worker
  // threads and a failure would not be optimal but should not be fatal.
  template <class WorkerType>
  static uint add_workers (WorkerType* holder,
                           uint active_workers,
                           uint total_workers,
                           uint created_workers,
                           os::ThreadType worker_type,
                           bool initializing) {
    uint start = created_workers;
    uint end = MIN2(active_workers, total_workers);
    for (uint worker_id = start; worker_id < end; worker_id += 1) {
      WorkerThread* new_worker = NULL;
      if (initializing || !InjectGCWorkerCreationFailure) {
        new_worker = holder->install_worker(worker_id);
      }
      if (new_worker == NULL || !os::create_thread(new_worker, worker_type)) {
        log_trace(gc, task)("WorkerManager::add_workers() : "
                            "creation failed due to failed allocation of native %s",
                            new_worker == NULL ?  "memory" : "thread");
        if (new_worker != NULL) {
           delete new_worker;
        }
        if (initializing) {
          vm_exit_out_of_memory(0, OOM_MALLOC_ERROR, "Cannot create worker GC thread. Out of system resources.");
        }
        break;
      }
      created_workers++;
      os::start_thread(new_worker);
    }

    log_trace(gc, task)("WorkerManager::add_workers() : "
                        "created_workers: %u", created_workers);

    return created_workers;
  }

  // Log (at trace level) a change in the number of created workers.
  template <class WorkerType>
  static void log_worker_creation(WorkerType* holder,
                                  uint previous_created_workers,
                                  uint active_workers,
                                  uint created_workers,
                                  bool initializing) {
    if (previous_created_workers < created_workers) {
      const char* initializing_msg =  initializing ? "Adding initial" : "Creating additional";
      log_trace(gc, task)("%s %s(s) previously created workers %u active workers %u total created workers %u",
                          initializing_msg, holder->group_name(), previous_created_workers, active_workers, created_workers);
    }
  }
};
#endif // SHARE_VM_GC_SHARED_WORKERMANAGER_HPP