path: root/src/share/vm/gc_implementation/concurrentMarkSweep/freeList.cpp

/*
 * Copyright 2001-2008 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 */

# include "incls/_precompiled.incl"
# include "incls/_freeList.cpp.incl"

// Free list.  A FreeList is used to access a linked list of chunks
// of space in the heap.  The head and tail are maintained so that
// items can be (as in the current implementation) added at the
// at the tail of the list and removed from the head of the list to
// maintain a FIFO queue.

FreeList::FreeList() :
  _head(NULL), _tail(NULL)
#ifdef ASSERT
  , _protecting_lock(NULL)
#endif
{
  _size         = 0;
  _count        = 0;
  _hint         = 0;
  init_statistics();
}

FreeList::FreeList(FreeChunk* fc) :
  _head(fc), _tail(fc)
#ifdef ASSERT
  , _protecting_lock(NULL)
#endif
{
  _size         = fc->size();
  _count        = 1;
  _hint         = 0;
  init_statistics();
#ifndef PRODUCT
  _allocation_stats.set_returnedBytes(size() * HeapWordSize);
#endif
}

FreeList::FreeList(HeapWord* addr, size_t size) :
  _head((FreeChunk*) addr), _tail((FreeChunk*) addr)
#ifdef ASSERT
  , _protecting_lock(NULL)
#endif
{
  assert(size > sizeof(FreeChunk), "size is too small");
  head()->setSize(size);
  _size         = size;
  _count        = 1;
  init_statistics();
#ifndef PRODUCT
  _allocation_stats.set_returnedBytes(_size * HeapWordSize);
#endif
}

void FreeList::reset(size_t hint) {
  set_count(0);
  set_head(NULL);
  set_tail(NULL);
  set_hint(hint);
}

void FreeList::init_statistics() {
  _allocation_stats.initialize();
}

FreeChunk* FreeList::getChunkAtHead() {
  assert_proper_lock_protection();
  assert(head() == NULL || head()->prev() == NULL, "list invariant");
  assert(tail() == NULL || tail()->next() == NULL, "list invariant");
  FreeChunk* fc = head();
  if (fc != NULL) {
    FreeChunk* nextFC = fc->next();
    if (nextFC != NULL) {
      // The chunk fc being removed has a "next".  Set the "next" to the
      // "prev" of fc.
      nextFC->linkPrev(NULL);
    } else { // removed tail of list
      link_tail(NULL);
    }
    link_head(nextFC);
    decrement_count();
  }
  assert(head() == NULL || head()->prev() == NULL, "list invariant");
  assert(tail() == NULL || tail()->next() == NULL, "list invariant");
  return fc;
}


void FreeList::getFirstNChunksFromList(size_t n, FreeList* fl) {
  assert_proper_lock_protection();
  assert(fl->count() == 0, "Precondition");
  if (count() > 0) {
    int k = 1;
    fl->set_head(head()); n--;
    FreeChunk* tl = head();
    while (tl->next() != NULL && n > 0) {
      tl = tl->next(); n--; k++;
    }
    assert(tl != NULL, "Loop Inv.");

    // First, fix up the list we took from.
    FreeChunk* new_head = tl->next();
    set_head(new_head);
    set_count(count() - k);
    if (new_head == NULL) {
      set_tail(NULL);
    } else {
      new_head->linkPrev(NULL);
    }
    // Now we can fix up the tail.
    tl->linkNext(NULL);
    // And return the result.
    fl->set_tail(tl);
    fl->set_count(k);
  }
}

// Remove this chunk from the list
void FreeList::removeChunk(FreeChunk*fc) {
   assert_proper_lock_protection();
   assert(head() != NULL, "Remove from empty list");
   assert(fc != NULL, "Remove a NULL chunk");
   assert(size() == fc->size(), "Wrong list");
   assert(head() == NULL || head()->prev() == NULL, "list invariant");
   assert(tail() == NULL || tail()->next() == NULL, "list invariant");

   FreeChunk* prevFC = fc->prev();
   FreeChunk* nextFC = fc->next();
   if (nextFC != NULL) {
     // The chunk fc being removed has a "next".  Set the "next" to the
     // "prev" of fc.
     nextFC->linkPrev(prevFC);
   } else { // removed tail of list
     link_tail(prevFC);
   }
   if (prevFC == NULL) { // removed head of list
     link_head(nextFC);
     assert(nextFC == NULL || nextFC->prev() == NULL,
       "Prev of head should be NULL");
   } else {
     prevFC->linkNext(nextFC);
     assert(tail() != prevFC || prevFC->next() == NULL,
       "Next of tail should be NULL");
   }
   decrement_count();
#define TRAP_CODE 1
#if TRAP_CODE
   if (head() == NULL) {
     guarantee(tail() == NULL, "INVARIANT");
     guarantee(count() == 0, "INVARIANT");
   }
#endif
   // clear next and prev fields of fc, debug only
   NOT_PRODUCT(
     fc->linkPrev(NULL);
     fc->linkNext(NULL);
   )
   assert(fc->isFree(), "Should still be a free chunk");
   assert(head() == NULL || head()->prev() == NULL, "list invariant");
   assert(tail() == NULL || tail()->next() == NULL, "list invariant");
   assert(head() == NULL || head()->size() == size(), "wrong item on list");
   assert(tail() == NULL || tail()->size() == size(), "wrong item on list");
}

// Add this chunk at the head of the list.
void FreeList::returnChunkAtHead(FreeChunk* chunk, bool record_return) {
  assert_proper_lock_protection();
  assert(chunk != NULL, "insert a NULL chunk");
  assert(size() == chunk->size(), "Wrong size");
  assert(head() == NULL || head()->prev() == NULL, "list invariant");
  assert(tail() == NULL || tail()->next() == NULL, "list invariant");

  FreeChunk* oldHead = head();
  assert(chunk != oldHead, "double insertion");
  chunk->linkAfter(oldHead);
  link_head(chunk);
  if (oldHead == NULL) { // only chunk in list
    assert(tail() == NULL, "inconsistent FreeList");
    link_tail(chunk);
  }
  increment_count(); // of # of chunks in list
  DEBUG_ONLY(
    if (record_return) {
      increment_returnedBytes_by(size()*HeapWordSize);
    }
  )
  assert(head() == NULL || head()->prev() == NULL, "list invariant");
  assert(tail() == NULL || tail()->next() == NULL, "list invariant");
  assert(head() == NULL || head()->size() == size(), "wrong item on list");
  assert(tail() == NULL || tail()->size() == size(), "wrong item on list");
}

void FreeList::returnChunkAtHead(FreeChunk* chunk) {
  assert_proper_lock_protection();
  returnChunkAtHead(chunk, true);
}

// Add this chunk at the tail of the list.
void FreeList::returnChunkAtTail(FreeChunk* chunk, bool record_return) {
  assert_proper_lock_protection();
  assert(head() == NULL || head()->prev() == NULL, "list invariant");
  assert(tail() == NULL || tail()->next() == NULL, "list invariant");
  assert(chunk != NULL, "insert a NULL chunk");
  assert(size() == chunk->size(), "wrong size");

  FreeChunk* oldTail = tail();
  assert(chunk != oldTail, "double insertion");
  if (oldTail != NULL) {
    oldTail->linkAfter(chunk);
  } else { // only chunk in list
    assert(head() == NULL, "inconsistent FreeList");
    link_head(chunk);
  }
  link_tail(chunk);
  increment_count();  // of # of chunks in list
  DEBUG_ONLY(
    if (record_return) {
      increment_returnedBytes_by(size()*HeapWordSize);
    }
  )
  assert(head() == NULL || head()->prev() == NULL, "list invariant");
  assert(tail() == NULL || tail()->next() == NULL, "list invariant");
  assert(head() == NULL || head()->size() == size(), "wrong item on list");
  assert(tail() == NULL || tail()->size() == size(), "wrong item on list");
}

void FreeList::returnChunkAtTail(FreeChunk* chunk) {
  returnChunkAtTail(chunk, true);
}

void FreeList::prepend(FreeList* fl) {
  assert_proper_lock_protection();
  if (fl->count() > 0) {
    if (count() == 0) {
      set_head(fl->head());
      set_tail(fl->tail());
      set_count(fl->count());
    } else {
      // Both are non-empty.
      FreeChunk* fl_tail = fl->tail();
      FreeChunk* this_head = head();
      assert(fl_tail->next() == NULL, "Well-formedness of fl");
      fl_tail->linkNext(this_head);
      this_head->linkPrev(fl_tail);
      set_head(fl->head());
      set_count(count() + fl->count());
    }
    fl->set_head(NULL);
    fl->set_tail(NULL);
    fl->set_count(0);
  }
}

// verifyChunkInFreeLists() is used to verify that an item is in this free list.
// It is used as a debugging aid.
bool FreeList::verifyChunkInFreeLists(FreeChunk* fc) const {
  // This is an internal consistency check, not part of the check that the
  // chunk is in the free lists.
  guarantee(fc->size() == size(), "Wrong list is being searched");
  FreeChunk* curFC = head();
  while (curFC) {
    // This is an internal consistency check.
    guarantee(size() == curFC->size(), "Chunk is in wrong list.");
    if (fc == curFC) {
      return true;
    }
    curFC = curFC->next();
  }
  return false;
}

#ifndef PRODUCT
void FreeList::assert_proper_lock_protection_work() const {
#ifdef ASSERT
  if (_protecting_lock != NULL &&
      SharedHeap::heap()->n_par_threads() > 0) {
    // Should become an assert.
    guarantee(_protecting_lock->owned_by_self(), "FreeList RACE DETECTED");
  }
#endif
}
#endif

// Print the "label line" for free list stats.
void FreeList::print_labels_on(outputStream* st, const char* c) {
  st->print("%16s\t", c);
  st->print("%14s\t"    "%14s\t"    "%14s\t"    "%14s\t"    "%14s\t"
            "%14s\t"    "%14s\t"    "%14s\t"    "%14s\t"    "%14s\t"    "\n",
            "bfrsurp", "surplus", "desired", "prvSwep", "bfrSwep",
            "count",   "cBirths", "cDeaths", "sBirths", "sDeaths");
}

// Print the AllocationStats for the given free list. If the second argument
// to the call is a non-null string, it is printed in the first column;
// otherwise, if the argument is null (the default), then the size of the
// (free list) block is printed in the first column.
void FreeList::print_on(outputStream* st, const char* c) const {
  if (c != NULL) {
    st->print("%16s", c);
  } else {
    st->print(SIZE_FORMAT_W(16), size());
  }
  st->print("\t"
           SSIZE_FORMAT_W(14) "\t" SSIZE_FORMAT_W(14) "\t" SSIZE_FORMAT_W(14) "\t" SSIZE_FORMAT_W(14) "\t" SSIZE_FORMAT_W(14) "\t"
           SSIZE_FORMAT_W(14) "\t" SSIZE_FORMAT_W(14) "\t" SSIZE_FORMAT_W(14) "\t" SSIZE_FORMAT_W(14) "\t" SSIZE_FORMAT_W(14) "\n",
           bfrSurp(),             surplus(),             desired(),             prevSweep(),           beforeSweep(),
           count(),               coalBirths(),          coalDeaths(),          splitBirths(),         splitDeaths());
}