#ifdef USE_PRAGMA_IDENT_SRC
#pragma ident "@(#)parGCAllocBuffer.cpp	1.27 07/05/05 17:05:53 JVM"
#endif
/*
 * Copyright 2001-2006 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/_parGCAllocBuffer.cpp.incl"

ParGCAllocBuffer::ParGCAllocBuffer(size_t desired_plab_sz_) :
  _word_sz(desired_plab_sz_), _bottom(NULL), _top(NULL),
  _end(NULL), _hard_end(NULL),
  _retained(false), _retained_filler(),
  _allocated(0), _wasted(0)
{
  assert (min_size() > AlignmentReserve, "Inconsistency!");
}

const size_t ParGCAllocBuffer::FillerHeaderSize =
             align_object_size(arrayOopDesc::header_size(T_INT));

// If the minimum object size is greater than MinObjAlignment, we can
// end up with a shard at the end of the buffer that's smaller than
// the smallest object.  We can't allow that because the buffer must
// look like it's full of objects when we retire it, so we make
// sure we have enough space for a filler int array object.
const size_t ParGCAllocBuffer::AlignmentReserve =
             oopDesc::header_size() > MinObjAlignment ? FillerHeaderSize : 0;

void ParGCAllocBuffer::retire(bool end_of_gc, bool retain) {
  assert(!retain || end_of_gc, "Can only retain at GC end.");
  if (_retained) {
    // If the buffer had been retained shorten the previous filler object.
    assert(_retained_filler.end() <= _top, "INVARIANT");
    SharedHeap::fill_region_with_object(_retained_filler);
    // Wasted space book-keeping, otherwise (normally) done in invalidate()
    _wasted += _retained_filler.word_size();
    _retained = false;
  }
  assert(!end_of_gc || !_retained, "At this point, end_of_gc ==> !_retained.");
  if (_top < _hard_end) {
    SharedHeap::fill_region_with_object(MemRegion(_top, _hard_end));
    if (!retain) {
      invalidate();
    } else {
      // Is there wasted space we'd like to retain for the next GC?
      if (pointer_delta(_end, _top) > FillerHeaderSize) {
	_retained = true;
	_retained_filler = MemRegion(_top, FillerHeaderSize);
	_top = _top + FillerHeaderSize;
      } else {
        invalidate();
      }
    }
  }
}

void ParGCAllocBuffer::flush_stats(PLABStats* stats) {
  assert(ResizePLAB, "Wasted work");
  stats->add_allocated(_allocated);
  stats->add_wasted(_wasted);
  stats->add_unused(pointer_delta(_end, _top));
}

// Compute desired plab size and latch result for later
// use. This should be called once at the end of parallel
// scavenge; it clears the sensor accumulators.
void PLABStats::adjust_desired_plab_sz() {
  assert(ResizePLAB, "Not set");
  if (_allocated == 0) {
    assert(_unused == 0, "Inconsistency in PLAB stats");
    _allocated = 1;
  }
  double wasted_frac    = (double)_unused/(double)_allocated;
  size_t target_refills = (size_t)((wasted_frac*TargetSurvivorRatio)/
                                   TargetPLABWastePct);
  if (target_refills == 0) {
    target_refills = 1;
  }
  _used = _allocated - _wasted - _unused;
  size_t plab_sz = _used/(target_refills*ParallelGCThreads);
  if (PrintPLAB) gclog_or_tty->print(" (plab_sz = %d ", plab_sz);
  // Take historical weighted average
  _filter.sample(plab_sz);
  // Clip from above and below, and align to object boundary
  plab_sz = MAX2(min_size(), (size_t)_filter.average());
  plab_sz = MIN2(max_size(), plab_sz);
  plab_sz = align_object_size(plab_sz);
  // Latch the result
  if (PrintPLAB) gclog_or_tty->print(" desired_plab_sz = %d) ", plab_sz);
  if (ResizePLAB) {
    _desired_plab_sz = plab_sz;
  }
  // Now clear the accumulators for next round:
  // note this needs to be fixed in the case where we
  // are retaining across scavenges. FIX ME !!! XXX
  _allocated = 0;
  _wasted    = 0;
  _unused    = 0;
}

#ifndef PRODUCT
void ParGCAllocBuffer::print() {
  gclog_or_tty->print("parGCAllocBuffer: _bottom: %p  _top: %p  _end: %p  _hard_end: %p"
             "_retained: %c _retained_filler: [%p,%p)\n",
             _bottom, _top, _end, _hard_end,
             "FT"[_retained], _retained_filler.start(), _retained_filler.end());
}
#endif // !PRODUCT