--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/g1/g1BlockOffsetTable.hpp Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,235 @@
+/*
+ * Copyright (c) 2001, 2017, 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_G1_G1BLOCKOFFSETTABLE_HPP
+#define SHARE_VM_GC_G1_G1BLOCKOFFSETTABLE_HPP
+
+#include "gc/g1/g1RegionToSpaceMapper.hpp"
+#include "gc/shared/blockOffsetTable.hpp"
+#include "memory/memRegion.hpp"
+#include "memory/virtualspace.hpp"
+#include "utilities/globalDefinitions.hpp"
+
+// Forward declarations
+class G1BlockOffsetTable;
+class G1ContiguousSpace;
+
+// This implementation of "G1BlockOffsetTable" divides the covered region
+// into "N"-word subregions (where "N" = 2^"LogN". An array with an entry
+// for each such subregion indicates how far back one must go to find the
+// start of the chunk that includes the first word of the subregion.
+//
+// Each G1BlockOffsetTablePart is owned by a G1ContiguousSpace.
+
+class G1BlockOffsetTable: public CHeapObj<mtGC> {
+ friend class G1BlockOffsetTablePart;
+ friend class VMStructs;
+
+private:
+ // The reserved region covered by the table.
+ MemRegion _reserved;
+
+ // Array for keeping offsets for retrieving object start fast given an
+ // address.
+ u_char* _offset_array; // byte array keeping backwards offsets
+
+ void check_offset(size_t offset, const char* msg) const {
+ assert(offset <= BOTConstants::N_words,
+ "%s - offset: " SIZE_FORMAT ", N_words: %u",
+ msg, offset, BOTConstants::N_words);
+ }
+
+ // Bounds checking accessors:
+ // For performance these have to devolve to array accesses in product builds.
+ inline u_char offset_array(size_t index) const;
+
+ void set_offset_array_raw(size_t index, u_char offset) {
+ _offset_array[index] = offset;
+ }
+
+ inline void set_offset_array(size_t index, u_char offset);
+
+ inline void set_offset_array(size_t index, HeapWord* high, HeapWord* low);
+
+ inline void set_offset_array(size_t left, size_t right, u_char offset);
+
+ bool is_card_boundary(HeapWord* p) const;
+
+ void check_index(size_t index, const char* msg) const NOT_DEBUG_RETURN;
+
+public:
+
+ // Return the number of slots needed for an offset array
+ // that covers mem_region_words words.
+ static size_t compute_size(size_t mem_region_words) {
+ size_t number_of_slots = (mem_region_words / BOTConstants::N_words);
+ return ReservedSpace::allocation_align_size_up(number_of_slots);
+ }
+
+ // Returns how many bytes of the heap a single byte of the BOT corresponds to.
+ static size_t heap_map_factor() {
+ return BOTConstants::N_bytes;
+ }
+
+ // Initialize the Block Offset Table to cover the memory region passed
+ // in the heap parameter.
+ G1BlockOffsetTable(MemRegion heap, G1RegionToSpaceMapper* storage);
+
+ // Return the appropriate index into "_offset_array" for "p".
+ inline size_t index_for(const void* p) const;
+ inline size_t index_for_raw(const void* p) const;
+
+ // Return the address indicating the start of the region corresponding to
+ // "index" in "_offset_array".
+ inline HeapWord* address_for_index(size_t index) const;
+ // Variant of address_for_index that does not check the index for validity.
+ inline HeapWord* address_for_index_raw(size_t index) const {
+ return _reserved.start() + (index << BOTConstants::LogN_words);
+ }
+};
+
+class G1BlockOffsetTablePart VALUE_OBJ_CLASS_SPEC {
+ friend class G1BlockOffsetTable;
+ friend class VMStructs;
+private:
+ // allocation boundary at which offset array must be updated
+ HeapWord* _next_offset_threshold;
+ size_t _next_offset_index; // index corresponding to that boundary
+
+ // Indicates if an object can span into this G1BlockOffsetTablePart.
+ debug_only(bool _object_can_span;)
+
+ // This is the global BlockOffsetTable.
+ G1BlockOffsetTable* _bot;
+
+ // The space that owns this subregion.
+ G1ContiguousSpace* _space;
+
+ // Sets the entries
+ // corresponding to the cards starting at "start" and ending at "end"
+ // to point back to the card before "start": the interval [start, end)
+ // is right-open.
+ void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end);
+ // Same as above, except that the args here are a card _index_ interval
+ // that is closed: [start_index, end_index]
+ void set_remainder_to_point_to_start_incl(size_t start, size_t end);
+
+ // Zero out the entry for _bottom (offset will be zero). Does not check for availability of the
+ // memory first.
+ void zero_bottom_entry_raw();
+ // Variant of initialize_threshold that does not check for availability of the
+ // memory first.
+ HeapWord* initialize_threshold_raw();
+
+ inline size_t block_size(const HeapWord* p) const;
+
+ // Returns the address of a block whose start is at most "addr".
+ // If "has_max_index" is true, "assumes "max_index" is the last valid one
+ // in the array.
+ inline HeapWord* block_at_or_preceding(const void* addr,
+ bool has_max_index,
+ size_t max_index) const;
+
+ // "q" is a block boundary that is <= "addr"; "n" is the address of the
+ // next block (or the end of the space.) Return the address of the
+ // beginning of the block that contains "addr". Does so without side
+ // effects (see, e.g., spec of block_start.)
+ inline HeapWord* forward_to_block_containing_addr_const(HeapWord* q, HeapWord* n,
+ const void* addr) const;
+
+ // "q" is a block boundary that is <= "addr"; return the address of the
+ // beginning of the block that contains "addr". May have side effects
+ // on "this", by updating imprecise entries.
+ inline HeapWord* forward_to_block_containing_addr(HeapWord* q,
+ const void* addr);
+
+ // "q" is a block boundary that is <= "addr"; "n" is the address of the
+ // next block (or the end of the space.) Return the address of the
+ // beginning of the block that contains "addr". May have side effects
+ // on "this", by updating imprecise entries.
+ HeapWord* forward_to_block_containing_addr_slow(HeapWord* q,
+ HeapWord* n,
+ const void* addr);
+
+ // Requires that "*threshold_" be the first array entry boundary at or
+ // above "blk_start", and that "*index_" be the corresponding array
+ // index. If the block starts at or crosses "*threshold_", records
+ // "blk_start" as the appropriate block start for the array index
+ // starting at "*threshold_", and for any other indices crossed by the
+ // block. Updates "*threshold_" and "*index_" to correspond to the first
+ // index after the block end.
+ void alloc_block_work(HeapWord** threshold_, size_t* index_,
+ HeapWord* blk_start, HeapWord* blk_end);
+
+ void check_all_cards(size_t left_card, size_t right_card) const;
+
+public:
+ // The elements of the array are initialized to zero.
+ G1BlockOffsetTablePart(G1BlockOffsetTable* array, G1ContiguousSpace* gsp);
+
+ void verify() const;
+
+ // Returns the address of the start of the block containing "addr", or
+ // else "null" if it is covered by no block. (May have side effects,
+ // namely updating of shared array entries that "point" too far
+ // backwards. This can occur, for example, when lab allocation is used
+ // in a space covered by the table.)
+ inline HeapWord* block_start(const void* addr);
+ // Same as above, but does not have any of the possible side effects
+ // discussed above.
+ inline HeapWord* block_start_const(const void* addr) const;
+
+ // Initialize the threshold to reflect the first boundary after the
+ // bottom of the covered region.
+ HeapWord* initialize_threshold();
+
+ void reset_bot() {
+ zero_bottom_entry_raw();
+ initialize_threshold_raw();
+ }
+
+ // Return the next threshold, the point at which the table should be
+ // updated.
+ HeapWord* threshold() const { return _next_offset_threshold; }
+
+ // These must be guaranteed to work properly (i.e., do nothing)
+ // when "blk_start" ("blk" for second version) is "NULL". In this
+ // implementation, that's true because NULL is represented as 0, and thus
+ // never exceeds the "_next_offset_threshold".
+ void alloc_block(HeapWord* blk_start, HeapWord* blk_end) {
+ if (blk_end > _next_offset_threshold) {
+ alloc_block_work(&_next_offset_threshold, &_next_offset_index, blk_start, blk_end);
+ }
+ }
+ void alloc_block(HeapWord* blk, size_t size) {
+ alloc_block(blk, blk+size);
+ }
+
+ void set_for_starts_humongous(HeapWord* obj_top, size_t fill_size);
+ void set_object_can_span(bool can_span) NOT_DEBUG_RETURN;
+
+ void print_on(outputStream* out) PRODUCT_RETURN;
+};
+
+#endif // SHARE_VM_GC_G1_G1BLOCKOFFSETTABLE_HPP