/*

 * 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/zErrno.hpp"

#include "gc/z/zGlobals.hpp"

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

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

#include "logging/log.hpp"

#include "runtime/atomic.hpp"

#include "utilities/debug.hpp"

#include <sys/mman.h>

#include <sys/types.h>

ZMarkStackSpace::ZMarkStackSpace() :

    _expand_lock(),

    _top(0),

    _end(0) {

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

  assert(ZMarkStacksMax <= ZMarkStackSpaceSize, "ZMarkStacksMax too large");

  // Reserve address space

  const void* res = mmap((void*)ZMarkStackSpaceStart, ZMarkStackSpaceSize,

                         PROT_NONE, MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE, -1, 0);

  if (res != (void*)ZMarkStackSpaceStart) {

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

    return;

  }

  // Successfully initialized

  _top = _end = ZMarkStackSpaceStart;

}

bool ZMarkStackSpace::is_initialized() const {

  return _top != 0;

}

bool ZMarkStackSpace::expand() {

  const size_t max = ZMarkStackSpaceStart + ZMarkStacksMax;

  if (_end + ZMarkStackSpaceExpandSize > max) {

    // Expansion limit reached

    return false;

  }

  void* const res = mmap((void*)_end, ZMarkStackSpaceExpandSize,

                         PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_PRIVATE|MAP_FIXED, -1, 0);

  if (res == MAP_FAILED) {

    ZErrno err;

    log_error(gc, marking)("Failed to map memory for marking stacks (%s)", err.to_string());

    return false;

  }

  return true;

}

uintptr_t ZMarkStackSpace::alloc_space(size_t size) {

  uintptr_t top = _top;

  for (;;) {

    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 locker(&_expand_lock);

  // Retry allocation before expanding

  uintptr_t addr = alloc_space(size);

  if (addr != 0) {

    return addr;

  }

  // Expand stack space

  if (!expand()) {

    // We currently can't handle the situation where we

    // are running out of mark stack space.

    fatal("Mark stack overflow (allocated " SIZE_FORMAT "M, size " SIZE_FORMAT "M, max " SIZE_FORMAT "M),"

          " use -XX:ZMarkStacksMax=? to increase this limit",

          (_end - ZMarkStackSpaceStart) / M, size / M, ZMarkStacksMax / M);

    return 0;

  }

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

                         (_end - ZMarkStackSpaceStart) / M,

                         (_end - ZMarkStackSpaceStart + ZMarkStackSpaceExpandSize) / M);

  // Increment top before end to make sure another

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

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

  _end += ZMarkStackSpaceExpandSize;

  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

  ZMarkStackMagazine* const magazine = _freelist.pop_atomic();

  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) {

  _freelist.push_atomic(magazine);

}

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;

  }

}