/*

 * Copyright (c) 2015, 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 "gc/z/zGlobals.hpp"

#include "gc/z/zTask.hpp"

#include "gc/z/zThread.hpp"

#include "gc/z/zWorkers.inline.hpp"

#include "runtime/os.hpp"

#include "runtime/mutexLocker.hpp"

#include "runtime/safepoint.hpp"

static uint calculate_nworkers_based_on_ncpus(double cpu_share_in_percent) {

  return ceil(os::initial_active_processor_count() * cpu_share_in_percent / 100.0);

}

static uint calculate_nworkers_based_on_heap_size(double reserve_share_in_percent) {

  const int nworkers = ((MaxHeapSize * (reserve_share_in_percent / 100.0)) - ZPageSizeMedium) / ZPageSizeSmall;

  return MAX2(nworkers, 1);

}

static uint calculate_nworkers(double cpu_share_in_percent) {

  // Cap number of workers so that we never use more than 10% of the max heap

  // for the reserve. This is useful when using small heaps on large machines.

  return MIN2(calculate_nworkers_based_on_ncpus(cpu_share_in_percent),

              calculate_nworkers_based_on_heap_size(10.0));

}

uint ZWorkers::calculate_nparallel() {

  // Use 60% of the CPUs, rounded up. We would like to use as many threads as

  // possible to increase parallelism. However, using a thread count that is

  // close to the number of processors tends to lead to over-provisioning and

  // scheduling latency issues. Using 60% of the active processors appears to

  // be a fairly good balance.

  return calculate_nworkers(60.0);

}

uint ZWorkers::calculate_nconcurrent() {

  // Use 12.5% of the CPUs, rounded up. The number of concurrent threads we

  // would like to use heavily depends on the type of workload we are running.

  // Using too many threads will have a negative impact on the application

  // throughput, while using too few threads will prolong the GC-cycle and

  // we then risk being out-run by the application. Using 12.5% of the active

  // processors appears to be a fairly good balance.

  return calculate_nworkers(12.5);

}

class ZWorkersInitializeTask : public ZTask {

private:

  const uint _nworkers;

  uint       _started;

  Monitor    _monitor;

public:

  ZWorkersInitializeTask(uint nworkers) :

      ZTask("ZWorkersInitializeTask"),

      _nworkers(nworkers),

      _started(0),

      _monitor(Monitor::leaf,

               "ZWorkersInitialize",

               false /* allow_vm_block */,

               Monitor::_safepoint_check_never) {}

  virtual void work() {

    // Register as worker

    ZThread::set_worker();

    // Wait for all threads to start

    MonitorLocker ml(&_monitor, Monitor::_no_safepoint_check_flag);

    if (++_started == _nworkers) {

      // All threads started

      ml.notify_all();

    } else {

      while (_started != _nworkers) {

        ml.wait();

      }

    }

  }

};

ZWorkers::ZWorkers() :

    _boost(false),

    _workers("ZWorker",

             nworkers(),

             true /* are_GC_task_threads */,

             true /* are_ConcurrentGC_threads */) {

  log_info(gc, init)("Workers: %u parallel, %u concurrent", nparallel(), nconcurrent());

  // Initialize worker threads

  _workers.initialize_workers();

  _workers.update_active_workers(nworkers());

  if (_workers.active_workers() != nworkers()) {

    vm_exit_during_initialization("Failed to create ZWorkers");

  }

  // Execute task to register threads as workers. This also helps

  // reduce latency in early GC pauses, which otherwise would have

  // to take on any warmup costs.

  ZWorkersInitializeTask task(nworkers());

  run(&task, nworkers());

}

void ZWorkers::set_boost(bool boost) {

  if (boost) {

    log_debug(gc)("Boosting workers");

  }

  _boost = boost;

}

void ZWorkers::run(ZTask* task, uint nworkers) {

  log_debug(gc, task)("Executing Task: %s, Active Workers: %u", task->name(), nworkers);

  _workers.update_active_workers(nworkers);

  _workers.run_task(task->gang_task());

}

void ZWorkers::run_parallel(ZTask* task) {

  assert(SafepointSynchronize::is_at_safepoint(), "Should be at a safepoint");

  run(task, nparallel());

}

void ZWorkers::run_concurrent(ZTask* task) {

  run(task, nconcurrent());

}

void ZWorkers::threads_do(ThreadClosure* tc) const {

  _workers.threads_do(tc);

}

void ZWorkers::print_threads_on(outputStream* st) const {

  _workers.print_worker_threads_on(st);

}