/*

 * Copyright (c) 2016, 2018, 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/zMarkStack.inline.hpp"

#include "logging/log.hpp"

#include "utilities/debug.hpp"

ZMarkStripe::ZMarkStripe() :

    _published(),

    _overflowed() {}

ZMarkStripeSet::ZMarkStripeSet() :

    _nstripes(0),

    _nstripes_mask(0),

    _stripes() {}

void ZMarkStripeSet::set_nstripes(size_t nstripes) {

  assert(is_power_of_2(nstripes), "Must be a power of two");

  assert(is_power_of_2(ZMarkStripesMax), "Must be a power of two");

  assert(nstripes >= 1, "Invalid number of stripes");

  assert(nstripes <= ZMarkStripesMax, "Invalid number of stripes");

  _nstripes = nstripes;

  _nstripes_mask = nstripes - 1;

  log_debug(gc, marking)("Using " SIZE_FORMAT " mark stripes", _nstripes);

}

bool ZMarkStripeSet::is_empty() const {

  for (size_t i = 0; i < _nstripes; i++) {

    if (!_stripes[i].is_empty()) {

      return false;

    }

  }

  return true;

}

ZMarkStripe* ZMarkStripeSet::stripe_for_worker(uint nworkers, uint worker_id) {

  const size_t spillover_limit = (nworkers / _nstripes) * _nstripes;

  size_t index;

  if (worker_id < spillover_limit) {

    // Not a spillover worker, use natural stripe

    index = worker_id & _nstripes_mask;

  } else {

    // Distribute spillover workers evenly across stripes

    const size_t spillover_nworkers = nworkers - spillover_limit;

    const size_t spillover_worker_id = worker_id - spillover_limit;

    const double spillover_chunk = (double)_nstripes / (double)spillover_nworkers;

    index = spillover_worker_id * spillover_chunk;

  }

  assert(index < _nstripes, "Invalid index");

  return &_stripes[index];

}

ZMarkThreadLocalStacks::ZMarkThreadLocalStacks() :

    _magazine(NULL) {

  for (size_t i = 0; i < ZMarkStripesMax; i++) {

    _stacks[i] = NULL;

  }

}

bool ZMarkThreadLocalStacks::is_empty(const ZMarkStripeSet* stripes) const {

  for (size_t i = 0; i < stripes->nstripes(); i++) {

    ZMarkStack* const stack = _stacks[i];

    if (stack != NULL) {

      return false;

    }

  }

  return true;

}

ZMarkStack* ZMarkThreadLocalStacks::allocate_stack(ZMarkStackAllocator* allocator) {

  if (_magazine == NULL) {

    // Allocate new magazine

    _magazine = allocator->alloc_magazine();

    if (_magazine == NULL) {

      return NULL;

    }

  }

  ZMarkStack* stack = NULL;

  if (!_magazine->pop(stack)) {

    // Magazine is empty, convert magazine into a new stack

    _magazine->~ZMarkStackMagazine();

    stack = new ((void*)_magazine) ZMarkStack();

    _magazine = NULL;

  }

  return stack;

}

void ZMarkThreadLocalStacks::free_stack(ZMarkStackAllocator* allocator, ZMarkStack* stack) {

  for (;;) {

    if (_magazine == NULL) {

      // Convert stack into a new magazine

      stack->~ZMarkStack();

      _magazine = new ((void*)stack) ZMarkStackMagazine();

      return;

    }

    if (_magazine->push(stack)) {

      // Success

      return;

    }

    // Free and uninstall full magazine

    allocator->free_magazine(_magazine);

    _magazine = NULL;

  }

}

bool ZMarkThreadLocalStacks::push_slow(ZMarkStackAllocator* allocator,

                                       ZMarkStripe* stripe,

                                       ZMarkStack** stackp,

                                       ZMarkStackEntry entry,

                                       bool publish) {

  ZMarkStack* stack = *stackp;

  for (;;) {

    if (stack == NULL) {

      // Allocate and install new stack

      *stackp = stack = allocate_stack(allocator);

      if (stack == NULL) {

        // Out of mark stack memory

        return false;

      }

    }

    if (stack->push(entry)) {

      // Success

      return true;

    }

    // Publish/Overflow and uninstall stack

    stripe->publish_stack(stack, publish);

    *stackp = stack = NULL;

  }

}

bool ZMarkThreadLocalStacks::pop_slow(ZMarkStackAllocator* allocator,

                                      ZMarkStripe* stripe,

                                      ZMarkStack** stackp,

                                      ZMarkStackEntry& entry) {

  ZMarkStack* stack = *stackp;

  for (;;) {

    if (stack == NULL) {

      // Try steal and install stack

      *stackp = stack = stripe->steal_stack();

      if (stack == NULL) {

        // Nothing to steal

        return false;

      }

    }

    if (stack->pop(entry)) {

      // Success

      return true;

    }

    // Free and uninstall stack

    free_stack(allocator, stack);

    *stackp = stack = NULL;

  }

}

bool ZMarkThreadLocalStacks::flush(ZMarkStackAllocator* allocator, ZMarkStripeSet* stripes) {

  bool flushed = false;

  // Flush all stacks

  for (size_t i = 0; i < stripes->nstripes(); i++) {

    ZMarkStripe* const stripe = stripes->stripe_at(i);

    ZMarkStack** const stackp = &_stacks[i];

    ZMarkStack* const stack = *stackp;

    if (stack == NULL) {

      continue;

    }

    // Free/Publish and uninstall stack

    if (stack->is_empty()) {

      free_stack(allocator, stack);

    } else {

      stripe->publish_stack(stack);

      flushed = true;

    }

    *stackp = NULL;

  }

  return flushed;

}

void ZMarkThreadLocalStacks::free(ZMarkStackAllocator* allocator) {

  // Free and uninstall magazine

  if (_magazine != NULL) {

    allocator->free_magazine(_magazine);

    _magazine = NULL;

  }

}