/*

 * Copyright (c) 2011, 2012, 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/g1AllocRegion.inline.hpp"

#include "gc_implementation/g1/g1CollectedHeap.inline.hpp"

G1CollectedHeap* G1AllocRegion::_g1h = NULL;

HeapRegion* G1AllocRegion::_dummy_region = NULL;

void G1AllocRegion::setup(G1CollectedHeap* g1h, HeapRegion* dummy_region) {

  assert(_dummy_region == NULL, "should be set once");

  assert(dummy_region != NULL, "pre-condition");

  assert(dummy_region->free() == 0, "pre-condition");

  // Make sure that any allocation attempt on this region will fail

  // and will not trigger any asserts.

  assert(allocate(dummy_region, 1, false) == NULL, "should fail");

  assert(par_allocate(dummy_region, 1, false) == NULL, "should fail");

  assert(allocate(dummy_region, 1, true) == NULL, "should fail");

  assert(par_allocate(dummy_region, 1, true) == NULL, "should fail");

  _g1h = g1h;

  _dummy_region = dummy_region;

}

void G1AllocRegion::fill_up_remaining_space(HeapRegion* alloc_region,

                                            bool bot_updates) {

  assert(alloc_region != NULL && alloc_region != _dummy_region,

         "pre-condition");

  // Other threads might still be trying to allocate using a CAS out

  // of the region we are trying to retire, as they can do so without

  // holding the lock. So, we first have to make sure that noone else

  // can allocate out of it by doing a maximal allocation. Even if our

  // CAS attempt fails a few times, we'll succeed sooner or later

  // given that failed CAS attempts mean that the region is getting

  // closed to being full.

  size_t free_word_size = alloc_region->free() / HeapWordSize;

  // This is the minimum free chunk we can turn into a dummy

  // object. If the free space falls below this, then noone can

  // allocate in this region anyway (all allocation requests will be

  // of a size larger than this) so we won't have to perform the dummy

  // allocation.

  size_t min_word_size_to_fill = CollectedHeap::min_fill_size();

  while (free_word_size >= min_word_size_to_fill) {

    HeapWord* dummy = par_allocate(alloc_region, free_word_size, bot_updates);

    if (dummy != NULL) {

      // If the allocation was successful we should fill in the space.

      CollectedHeap::fill_with_object(dummy, free_word_size);

      alloc_region->set_pre_dummy_top(dummy);

      break;

    }

    free_word_size = alloc_region->free() / HeapWordSize;

    // It's also possible that someone else beats us to the

    // allocation and they fill up the region. In that case, we can

    // just get out of the loop.

  }

  assert(alloc_region->free() / HeapWordSize < min_word_size_to_fill,

         "post-condition");

}

void G1AllocRegion::retire(bool fill_up) {

  assert(_alloc_region != NULL, ar_ext_msg(this, "not initialized properly"));

  trace("retiring");

  HeapRegion* alloc_region = _alloc_region;

  if (alloc_region != _dummy_region) {

    // We never have to check whether the active region is empty or not,

    // and potentially free it if it is, given that it's guaranteed that

    // it will never be empty.

    assert(!alloc_region->is_empty(),

           ar_ext_msg(this, "the alloc region should never be empty"));

    if (fill_up) {

      fill_up_remaining_space(alloc_region, _bot_updates);

    }

    assert(alloc_region->used() >= _used_bytes_before,

           ar_ext_msg(this, "invariant"));

    size_t allocated_bytes = alloc_region->used() - _used_bytes_before;

    retire_region(alloc_region, allocated_bytes);

    _used_bytes_before = 0;

    _alloc_region = _dummy_region;

  }

  trace("retired");

}

HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size,

                                                       bool force) {

  assert(_alloc_region == _dummy_region, ar_ext_msg(this, "pre-condition"));

  assert(_used_bytes_before == 0, ar_ext_msg(this, "pre-condition"));

  trace("attempting region allocation");

  HeapRegion* new_alloc_region = allocate_new_region(word_size, force);

  if (new_alloc_region != NULL) {

    new_alloc_region->reset_pre_dummy_top();

    // Need to do this before the allocation

    _used_bytes_before = new_alloc_region->used();

    HeapWord* result = allocate(new_alloc_region, word_size, _bot_updates);

    assert(result != NULL, ar_ext_msg(this, "the allocation should succeeded"));

    OrderAccess::storestore();

    // Note that we first perform the allocation and then we store the

    // region in _alloc_region. This is the reason why an active region

    // can never be empty.

    _alloc_region = new_alloc_region;

    _count += 1;

    trace("region allocation successful");

    return result;

  } else {

    trace("region allocation failed");

    return NULL;

  }

  ShouldNotReachHere();

}

void G1AllocRegion::fill_in_ext_msg(ar_ext_msg* msg, const char* message) {

  msg->append("[%s] %s c: %u b: %s r: "PTR_FORMAT" u: "SIZE_FORMAT,

              _name, message, _count, BOOL_TO_STR(_bot_updates),

              _alloc_region, _used_bytes_before);

}

void G1AllocRegion::init() {

  trace("initializing");

  assert(_alloc_region == NULL && _used_bytes_before == 0,

         ar_ext_msg(this, "pre-condition"));

  assert(_dummy_region != NULL, ar_ext_msg(this, "should have been set"));

  _alloc_region = _dummy_region;

  _count = 0;

  trace("initialized");

}

void G1AllocRegion::set(HeapRegion* alloc_region) {

  trace("setting");

  // We explicitly check that the region is not empty to make sure we

  // maintain the "the alloc region cannot be empty" invariant.

  assert(alloc_region != NULL && !alloc_region->is_empty(),

         ar_ext_msg(this, "pre-condition"));

  assert(_alloc_region == _dummy_region &&

         _used_bytes_before == 0 && _count == 0,

         ar_ext_msg(this, "pre-condition"));

  _used_bytes_before = alloc_region->used();

  _alloc_region = alloc_region;

  _count += 1;

  trace("set");

}

HeapRegion* G1AllocRegion::release() {

  trace("releasing");

  HeapRegion* alloc_region = _alloc_region;

  retire(false /* fill_up */);

  assert(_alloc_region == _dummy_region,

         ar_ext_msg(this, "post-condition of retire()"));

  _alloc_region = NULL;

  trace("released");

  return (alloc_region == _dummy_region) ? NULL : alloc_region;

}

#if G1_ALLOC_REGION_TRACING

void G1AllocRegion::trace(const char* str, size_t word_size, HeapWord* result) {

  // All the calls to trace that set either just the size or the size

  // and the result are considered part of level 2 tracing and are

  // skipped during level 1 tracing.

  if ((word_size == 0 && result == NULL) || (G1_ALLOC_REGION_TRACING > 1)) {

    const size_t buffer_length = 128;

    char hr_buffer[buffer_length];

    char rest_buffer[buffer_length];

    HeapRegion* alloc_region = _alloc_region;

    if (alloc_region == NULL) {

      jio_snprintf(hr_buffer, buffer_length, "NULL");

    } else if (alloc_region == _dummy_region) {

      jio_snprintf(hr_buffer, buffer_length, "DUMMY");

    } else {

      jio_snprintf(hr_buffer, buffer_length,

                   HR_FORMAT, HR_FORMAT_PARAMS(alloc_region));

    }

    if (G1_ALLOC_REGION_TRACING > 1) {

      if (result != NULL) {

        jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT" "PTR_FORMAT,

                     word_size, result);

      } else if (word_size != 0) {

        jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT, word_size);

      } else {

        jio_snprintf(rest_buffer, buffer_length, "");

      }

    } else {

      jio_snprintf(rest_buffer, buffer_length, "");

    }

    tty->print_cr("[%s] %u %s : %s %s",

                  _name, _count, hr_buffer, str, rest_buffer);

  }

}

#endif // G1_ALLOC_REGION_TRACING

G1AllocRegion::G1AllocRegion(const char* name,

                             bool bot_updates)

  : _name(name), _bot_updates(bot_updates),

    _alloc_region(NULL), _count(0), _used_bytes_before(0) { }