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/*
* Copyright (c) 2001, 2012, 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.
*
*/
#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
#define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
class HeapRegion;
class HeapRegionClosure;
class FreeRegionList;
// This class keeps track of the region metadata (i.e., HeapRegion
// instances). They are kept in the _regions array in address
// order. A region's index in the array corresponds to its index in
// the heap (i.e., 0 is the region at the bottom of the heap, 1 is
// the one after it, etc.). Two regions that are consecutive in the
// array should also be adjacent in the address space (i.e.,
// region(i).end() == region(i+1).bottom().
//
// We create a HeapRegion when we commit the region's address space
// for the first time. When we uncommit the address space of a
// region we retain the HeapRegion to be able to re-use it in the
// future (in case we recommit it).
//
// We keep track of three lengths:
//
// * _length (returned by length()) is the number of currently
// committed regions.
// * _allocated_length (not exposed outside this class) is the
// number of regions for which we have HeapRegions.
// * _max_length (returned by max_length()) is the maximum number of
// regions the heap can have.
//
// and maintain that: _length <= _allocated_length <= _max_length
class HeapRegionSeq: public CHeapObj {
friend class VMStructs;
// The array that holds the HeapRegions.
HeapRegion** _regions;
// Version of _regions biased to address 0
HeapRegion** _regions_biased;
// The number of regions committed in the heap.
uint _length;
// The address of the first reserved word in the heap.
HeapWord* _heap_bottom;
// The address of the last reserved word in the heap - 1.
HeapWord* _heap_end;
// The log of the region byte size.
uint _region_shift;
// A hint for which index to start searching from for humongous
// allocations.
uint _next_search_index;
// The number of regions for which we have allocated HeapRegions for.
uint _allocated_length;
// The maximum number of regions in the heap.
uint _max_length;
// Find a contiguous set of empty regions of length num, starting
// from the given index.
uint find_contiguous_from(uint from, uint num);
// Map a heap address to a biased region index. Assume that the
// address is valid.
inline uintx addr_to_index_biased(HeapWord* addr) const;
void increment_length(uint* length) {
assert(*length < _max_length, "pre-condition");
*length += 1;
}
void decrement_length(uint* length) {
assert(*length > 0, "pre-condition");
*length -= 1;
}
public:
// Empty contructor, we'll initialize it with the initialize() method.
HeapRegionSeq() { }
void initialize(HeapWord* bottom, HeapWord* end, uint max_length);
// Return the HeapRegion at the given index. Assume that the index
// is valid.
inline HeapRegion* at(uint index) const;
// If addr is within the committed space return its corresponding
// HeapRegion, otherwise return NULL.
inline HeapRegion* addr_to_region(HeapWord* addr) const;
// Return the HeapRegion that corresponds to the given
// address. Assume the address is valid.
inline HeapRegion* addr_to_region_unsafe(HeapWord* addr) const;
// Return the number of regions that have been committed in the heap.
uint length() const { return _length; }
// Return the maximum number of regions in the heap.
uint max_length() const { return _max_length; }
// Expand the sequence to reflect that the heap has grown from
// old_end to new_end. Either create new HeapRegions, or re-use
// existing ones, and return them in the given list. Returns the
// memory region that covers the newly-created regions. If a
// HeapRegion allocation fails, the result memory region might be
// smaller than the desired one.
MemRegion expand_by(HeapWord* old_end, HeapWord* new_end,
FreeRegionList* list);
// Return the number of contiguous regions at the end of the sequence
// that are available for allocation.
uint free_suffix();
// Find a contiguous set of empty regions of length num and return
// the index of the first region or G1_NULL_HRS_INDEX if the
// search was unsuccessful.
uint find_contiguous(uint num);
// Apply blk->doHeapRegion() on all committed regions in address order,
// terminating the iteration early if doHeapRegion() returns true.
void iterate(HeapRegionClosure* blk) const;
// As above, but start the iteration from hr and loop around. If hr
// is NULL, we start from the first region in the heap.
void iterate_from(HeapRegion* hr, HeapRegionClosure* blk) const;
// Tag as uncommitted as many regions that are completely free as
// possible, up to shrink_bytes, from the suffix of the committed
// sequence. Return a MemRegion that corresponds to the address
// range of the uncommitted regions. Assume shrink_bytes is page and
// heap region aligned.
MemRegion shrink_by(size_t shrink_bytes, uint* num_regions_deleted);
// Do some sanity checking.
void verify_optional() PRODUCT_RETURN;
};
#endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
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