/*

 * 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/zLock.inline.hpp"

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

#include "gc/z/zMarkStackAllocator.hpp"

#include "logging/log.hpp"

#include "runtime/atomic.hpp"

#include "runtime/os.hpp"

#include "utilities/debug.hpp"

uintptr_t ZMarkStackSpaceStart;

ZMarkStackSpace::ZMarkStackSpace() :

    _expand_lock(),

    _start(0),

    _top(0),

    _end(0) {

  assert(ZMarkStackSpaceLimit >= ZMarkStackSpaceExpandSize, "ZMarkStackSpaceLimit too small");

  // Reserve address space

  const size_t size = ZMarkStackSpaceLimit;

  const size_t alignment = (size_t)os::vm_allocation_granularity();

  const uintptr_t addr = (uintptr_t)os::reserve_memory(size, NULL, alignment, mtGC);

  if (addr == 0) {

    log_error(gc, marking)("Failed to reserve address space for mark stacks");

    return;

  }

  // Successfully initialized

  _start = _top = _end = addr;

  // Register mark stack space start

  ZMarkStackSpaceStart = _start;

}

bool ZMarkStackSpace::is_initialized() const {

  return _start != 0;

}

uintptr_t ZMarkStackSpace::alloc_space(size_t size) {

  uintptr_t top = Atomic::load(&_top);

  for (;;) {

    const uintptr_t end = Atomic::load(&_end);

    const uintptr_t new_top = top + size;

    if (new_top > end) {

      // Not enough space left

      return 0;

    }

    const uintptr_t prev_top = Atomic::cmpxchg(new_top, &_top, top);

    if (prev_top == top) {

      // Success

      return top;

    }

    // Retry

    top = prev_top;

  }

}

uintptr_t ZMarkStackSpace::expand_and_alloc_space(size_t size) {

  ZLocker<ZLock> locker(&_expand_lock);

  // Retry allocation before expanding

  uintptr_t addr = alloc_space(size);

  if (addr != 0) {

    return addr;

  }

  // Check expansion limit

  const size_t expand_size = ZMarkStackSpaceExpandSize;

  const size_t old_size = _end - _start;

  const size_t new_size = old_size + expand_size;

  if (new_size > ZMarkStackSpaceLimit) {

    // Expansion limit reached. This is a fatal error since we

    // currently can't recover from running out of mark stack space.

    fatal("Mark stack space exhausted. Use -XX:ZMarkStackSpaceLimit=<size> to increase the "

          "maximum number of bytes allocated for mark stacks. Current limit is " SIZE_FORMAT "M.",

          ZMarkStackSpaceLimit / M);

  }

  log_debug(gc, marking)("Expanding mark stack space: " SIZE_FORMAT "M->" SIZE_FORMAT "M",

                         old_size / M, new_size / M);

  // Expand

  os::commit_memory_or_exit((char*)_end, expand_size, false /* executable */, "Mark stack space");

  // Increment top before end to make sure another

  // thread can't steal out newly expanded space.

  addr = Atomic::add(size, &_top) - size;

  Atomic::add(expand_size, &_end);

  return addr;

}

uintptr_t ZMarkStackSpace::alloc(size_t size) {

  const uintptr_t addr = alloc_space(size);

  if (addr != 0) {

    return addr;

  }

  return expand_and_alloc_space(size);

}

ZMarkStackAllocator::ZMarkStackAllocator() :

    _freelist(),

    _space() {

  guarantee(sizeof(ZMarkStack) == ZMarkStackSize, "Size mismatch");

  guarantee(sizeof(ZMarkStackMagazine) <= ZMarkStackSize, "Size mismatch");

  // Prime free list to avoid an immediate space

  // expansion when marking starts.

  if (_space.is_initialized()) {

    prime_freelist();

  }

}

bool ZMarkStackAllocator::is_initialized() const {

  return _space.is_initialized();

}

void ZMarkStackAllocator::prime_freelist() {

  for (size_t size = 0; size < ZMarkStackSpaceExpandSize; size += ZMarkStackMagazineSize) {

    const uintptr_t addr = _space.alloc(ZMarkStackMagazineSize);

    ZMarkStackMagazine* const magazine = create_magazine_from_space(addr, ZMarkStackMagazineSize);

    free_magazine(magazine);

  }

}

ZMarkStackMagazine* ZMarkStackAllocator::create_magazine_from_space(uintptr_t addr, size_t size) {

  assert(is_aligned(size, ZMarkStackSize), "Invalid size");

  // Use first stack as magazine

  ZMarkStackMagazine* const magazine = new ((void*)addr) ZMarkStackMagazine();

  for (size_t i = ZMarkStackSize; i < size; i += ZMarkStackSize) {

    ZMarkStack* const stack = new ((void*)(addr + i)) ZMarkStack();

    const bool success = magazine->push(stack);

    assert(success, "Magazine should never get full");

  }

  return magazine;

}

ZMarkStackMagazine* ZMarkStackAllocator::alloc_magazine() {

  // Try allocating from the free list first

  if (magazine != NULL) {

    return magazine;

  }

  // Allocate new magazine

  const uintptr_t addr = _space.alloc(ZMarkStackMagazineSize);

  if (addr == 0) {

    return NULL;

  }

  return create_magazine_from_space(addr, ZMarkStackMagazineSize);

}

void ZMarkStackAllocator::free_magazine(ZMarkStackMagazine* magazine) {

}