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 /*

  * Copyright (c) 2001, 2010, 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.

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  */

 #include "precompiled.hpp"

 #include "gc_implementation/concurrentMarkSweep/freeBlockDictionary.hpp"

 #include "gc_implementation/concurrentMarkSweep/freeList.hpp"

 #include "memory/sharedHeap.hpp"

 #include "runtime/globals.hpp"

 #include "runtime/mutex.hpp"

 #include "runtime/vmThread.hpp"

 // 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(bool split_birth) {

   _allocation_stats.initialize(split_birth);

 }

 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();

    assert(((head() == NULL) + (tail() == NULL) + (count() == 0)) % 3 == 0,

           "H/T/C Inconsistency");

    // 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::verify_stats() const {

   // The +1 of the LH comparand is to allow some "looseness" in

   // checking: we usually call this interface when adding a block

   // and we'll subsequently update the stats; we cannot update the

   // stats beforehand because in the case of the large-block BT

   // dictionary for example, this might be the first block and

   // in that case there would be no place that we could record

   // the stats (which are kept in the block itself).

   assert(_allocation_stats.prevSweep() + _allocation_stats.splitBirths() + 1   // Total Stock + 1

           >= _allocation_stats.splitDeaths() + (ssize_t)count(), "Conservation Principle");

 }

 void FreeList::assert_proper_lock_protection_work() const {

   assert(_protecting_lock != NULL, "Don't call this directly");

   assert(ParallelGCThreads > 0, "Don't call this directly");

   Thread* thr = Thread::current();

   if (thr->is_VM_thread() || thr->is_ConcurrentGC_thread()) {

     // assert that we are holding the freelist lock

   } else if (thr->is_GC_task_thread()) {

     assert(_protecting_lock->owned_by_self(), "FreeList RACE DETECTED");

   } else if (thr->is_Java_thread()) {

     assert(!SafepointSynchronize::is_at_safepoint(), "Should not be executing");

   } else {

     ShouldNotReachHere();  // unaccounted thread type?

   }

 }

 #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());

 }