1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp Thu Jun 05 15:57:56 2008 -0700
1.3 @@ -0,0 +1,487 @@
1.4 +/*
1.5 + * Copyright 2001-2007 Sun Microsystems, Inc. All Rights Reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation.
1.11 + *
1.12 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.13 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.14 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.15 + * version 2 for more details (a copy is included in the LICENSE file that
1.16 + * accompanied this code).
1.17 + *
1.18 + * You should have received a copy of the GNU General Public License version
1.19 + * 2 along with this work; if not, write to the Free Software Foundation,
1.20 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.21 + *
1.22 + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
1.23 + * CA 95054 USA or visit www.sun.com if you need additional information or
1.24 + * have any questions.
1.25 + *
1.26 + */
1.27 +
1.28 +// The CollectedHeap type requires subtypes to implement a method
1.29 +// "block_start". For some subtypes, notably generational
1.30 +// systems using card-table-based write barriers, the efficiency of this
1.31 +// operation may be important. Implementations of the "BlockOffsetArray"
1.32 +// class may be useful in providing such efficient implementations.
1.33 +//
1.34 +// While generally mirroring the structure of the BOT for GenCollectedHeap,
1.35 +// the following types are tailored more towards G1's uses; these should,
1.36 +// however, be merged back into a common BOT to avoid code duplication
1.37 +// and reduce maintenance overhead.
1.38 +//
1.39 +// G1BlockOffsetTable (abstract)
1.40 +// -- G1BlockOffsetArray (uses G1BlockOffsetSharedArray)
1.41 +// -- G1BlockOffsetArrayContigSpace
1.42 +//
1.43 +// A main impediment to the consolidation of this code might be the
1.44 +// effect of making some of the block_start*() calls non-const as
1.45 +// below. Whether that might adversely affect performance optimizations
1.46 +// that compilers might normally perform in the case of non-G1
1.47 +// collectors needs to be carefully investigated prior to any such
1.48 +// consolidation.
1.49 +
1.50 +// Forward declarations
1.51 +class ContiguousSpace;
1.52 +class G1BlockOffsetSharedArray;
1.53 +
1.54 +class G1BlockOffsetTable VALUE_OBJ_CLASS_SPEC {
1.55 + friend class VMStructs;
1.56 +protected:
1.57 + // These members describe the region covered by the table.
1.58 +
1.59 + // The space this table is covering.
1.60 + HeapWord* _bottom; // == reserved.start
1.61 + HeapWord* _end; // End of currently allocated region.
1.62 +
1.63 +public:
1.64 + // Initialize the table to cover the given space.
1.65 + // The contents of the initial table are undefined.
1.66 + G1BlockOffsetTable(HeapWord* bottom, HeapWord* end) :
1.67 + _bottom(bottom), _end(end)
1.68 + {
1.69 + assert(_bottom <= _end, "arguments out of order");
1.70 + }
1.71 +
1.72 + // Note that the committed size of the covered space may have changed,
1.73 + // so the table size might also wish to change.
1.74 + virtual void resize(size_t new_word_size) = 0;
1.75 +
1.76 + virtual void set_bottom(HeapWord* new_bottom) {
1.77 + assert(new_bottom <= _end, "new_bottom > _end");
1.78 + _bottom = new_bottom;
1.79 + resize(pointer_delta(_end, _bottom));
1.80 + }
1.81 +
1.82 + // Requires "addr" to be contained by a block, and returns the address of
1.83 + // the start of that block. (May have side effects, namely updating of
1.84 + // shared array entries that "point" too far backwards. This can occur,
1.85 + // for example, when LAB allocation is used in a space covered by the
1.86 + // table.)
1.87 + virtual HeapWord* block_start_unsafe(const void* addr) = 0;
1.88 + // Same as above, but does not have any of the possible side effects
1.89 + // discussed above.
1.90 + virtual HeapWord* block_start_unsafe_const(const void* addr) const = 0;
1.91 +
1.92 + // Returns the address of the start of the block containing "addr", or
1.93 + // else "null" if it is covered by no block. (May have side effects,
1.94 + // namely updating of shared array entries that "point" too far
1.95 + // backwards. This can occur, for example, when lab allocation is used
1.96 + // in a space covered by the table.)
1.97 + inline HeapWord* block_start(const void* addr);
1.98 + // Same as above, but does not have any of the possible side effects
1.99 + // discussed above.
1.100 + inline HeapWord* block_start_const(const void* addr) const;
1.101 +};
1.102 +
1.103 +// This implementation of "G1BlockOffsetTable" divides the covered region
1.104 +// into "N"-word subregions (where "N" = 2^"LogN". An array with an entry
1.105 +// for each such subregion indicates how far back one must go to find the
1.106 +// start of the chunk that includes the first word of the subregion.
1.107 +//
1.108 +// Each BlockOffsetArray is owned by a Space. However, the actual array
1.109 +// may be shared by several BlockOffsetArrays; this is useful
1.110 +// when a single resizable area (such as a generation) is divided up into
1.111 +// several spaces in which contiguous allocation takes place,
1.112 +// such as, for example, in G1 or in the train generation.)
1.113 +
1.114 +// Here is the shared array type.
1.115 +
1.116 +class G1BlockOffsetSharedArray: public CHeapObj {
1.117 + friend class G1BlockOffsetArray;
1.118 + friend class G1BlockOffsetArrayContigSpace;
1.119 + friend class VMStructs;
1.120 +
1.121 +private:
1.122 + // The reserved region covered by the shared array.
1.123 + MemRegion _reserved;
1.124 +
1.125 + // End of the current committed region.
1.126 + HeapWord* _end;
1.127 +
1.128 + // Array for keeping offsets for retrieving object start fast given an
1.129 + // address.
1.130 + VirtualSpace _vs;
1.131 + u_char* _offset_array; // byte array keeping backwards offsets
1.132 +
1.133 + // Bounds checking accessors:
1.134 + // For performance these have to devolve to array accesses in product builds.
1.135 + u_char offset_array(size_t index) const {
1.136 + assert(index < _vs.committed_size(), "index out of range");
1.137 + return _offset_array[index];
1.138 + }
1.139 +
1.140 + void set_offset_array(size_t index, u_char offset) {
1.141 + assert(index < _vs.committed_size(), "index out of range");
1.142 + assert(offset <= N_words, "offset too large");
1.143 + _offset_array[index] = offset;
1.144 + }
1.145 +
1.146 + void set_offset_array(size_t index, HeapWord* high, HeapWord* low) {
1.147 + assert(index < _vs.committed_size(), "index out of range");
1.148 + assert(high >= low, "addresses out of order");
1.149 + assert(pointer_delta(high, low) <= N_words, "offset too large");
1.150 + _offset_array[index] = (u_char) pointer_delta(high, low);
1.151 + }
1.152 +
1.153 + void set_offset_array(HeapWord* left, HeapWord* right, u_char offset) {
1.154 + assert(index_for(right - 1) < _vs.committed_size(),
1.155 + "right address out of range");
1.156 + assert(left < right, "Heap addresses out of order");
1.157 + size_t num_cards = pointer_delta(right, left) >> LogN_words;
1.158 + memset(&_offset_array[index_for(left)], offset, num_cards);
1.159 + }
1.160 +
1.161 + void set_offset_array(size_t left, size_t right, u_char offset) {
1.162 + assert(right < _vs.committed_size(), "right address out of range");
1.163 + assert(left <= right, "indexes out of order");
1.164 + size_t num_cards = right - left + 1;
1.165 + memset(&_offset_array[left], offset, num_cards);
1.166 + }
1.167 +
1.168 + void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const {
1.169 + assert(index < _vs.committed_size(), "index out of range");
1.170 + assert(high >= low, "addresses out of order");
1.171 + assert(pointer_delta(high, low) <= N_words, "offset too large");
1.172 + assert(_offset_array[index] == pointer_delta(high, low),
1.173 + "Wrong offset");
1.174 + }
1.175 +
1.176 + bool is_card_boundary(HeapWord* p) const;
1.177 +
1.178 + // Return the number of slots needed for an offset array
1.179 + // that covers mem_region_words words.
1.180 + // We always add an extra slot because if an object
1.181 + // ends on a card boundary we put a 0 in the next
1.182 + // offset array slot, so we want that slot always
1.183 + // to be reserved.
1.184 +
1.185 + size_t compute_size(size_t mem_region_words) {
1.186 + size_t number_of_slots = (mem_region_words / N_words) + 1;
1.187 + return ReservedSpace::page_align_size_up(number_of_slots);
1.188 + }
1.189 +
1.190 +public:
1.191 + enum SomePublicConstants {
1.192 + LogN = 9,
1.193 + LogN_words = LogN - LogHeapWordSize,
1.194 + N_bytes = 1 << LogN,
1.195 + N_words = 1 << LogN_words
1.196 + };
1.197 +
1.198 + // Initialize the table to cover from "base" to (at least)
1.199 + // "base + init_word_size". In the future, the table may be expanded
1.200 + // (see "resize" below) up to the size of "_reserved" (which must be at
1.201 + // least "init_word_size".) The contents of the initial table are
1.202 + // undefined; it is the responsibility of the constituent
1.203 + // G1BlockOffsetTable(s) to initialize cards.
1.204 + G1BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size);
1.205 +
1.206 + // Notes a change in the committed size of the region covered by the
1.207 + // table. The "new_word_size" may not be larger than the size of the
1.208 + // reserved region this table covers.
1.209 + void resize(size_t new_word_size);
1.210 +
1.211 + void set_bottom(HeapWord* new_bottom);
1.212 +
1.213 + // Updates all the BlockOffsetArray's sharing this shared array to
1.214 + // reflect the current "top"'s of their spaces.
1.215 + void update_offset_arrays();
1.216 +
1.217 + // Return the appropriate index into "_offset_array" for "p".
1.218 + inline size_t index_for(const void* p) const;
1.219 +
1.220 + // Return the address indicating the start of the region corresponding to
1.221 + // "index" in "_offset_array".
1.222 + inline HeapWord* address_for_index(size_t index) const;
1.223 +};
1.224 +
1.225 +// And here is the G1BlockOffsetTable subtype that uses the array.
1.226 +
1.227 +class G1BlockOffsetArray: public G1BlockOffsetTable {
1.228 + friend class G1BlockOffsetSharedArray;
1.229 + friend class G1BlockOffsetArrayContigSpace;
1.230 + friend class VMStructs;
1.231 +private:
1.232 + enum SomePrivateConstants {
1.233 + N_words = G1BlockOffsetSharedArray::N_words,
1.234 + LogN = G1BlockOffsetSharedArray::LogN
1.235 + };
1.236 +
1.237 + // The following enums are used by do_block_helper
1.238 + enum Action {
1.239 + Action_single, // BOT records a single block (see single_block())
1.240 + Action_mark, // BOT marks the start of a block (see mark_block())
1.241 + Action_check // Check that BOT records block correctly
1.242 + // (see verify_single_block()).
1.243 + };
1.244 +
1.245 + // This is the array, which can be shared by several BlockOffsetArray's
1.246 + // servicing different
1.247 + G1BlockOffsetSharedArray* _array;
1.248 +
1.249 + // The space that owns this subregion.
1.250 + Space* _sp;
1.251 +
1.252 + // If "_sp" is a contiguous space, the field below is the view of "_sp"
1.253 + // as a contiguous space, else NULL.
1.254 + ContiguousSpace* _csp;
1.255 +
1.256 + // If true, array entries are initialized to 0; otherwise, they are
1.257 + // initialized to point backwards to the beginning of the covered region.
1.258 + bool _init_to_zero;
1.259 +
1.260 + // The portion [_unallocated_block, _sp.end()) of the space that
1.261 + // is a single block known not to contain any objects.
1.262 + // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag.
1.263 + HeapWord* _unallocated_block;
1.264 +
1.265 + // Sets the entries
1.266 + // corresponding to the cards starting at "start" and ending at "end"
1.267 + // to point back to the card before "start": the interval [start, end)
1.268 + // is right-open.
1.269 + void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end);
1.270 + // Same as above, except that the args here are a card _index_ interval
1.271 + // that is closed: [start_index, end_index]
1.272 + void set_remainder_to_point_to_start_incl(size_t start, size_t end);
1.273 +
1.274 + // A helper function for BOT adjustment/verification work
1.275 + void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action);
1.276 +
1.277 +protected:
1.278 +
1.279 + ContiguousSpace* csp() const { return _csp; }
1.280 +
1.281 + // Returns the address of a block whose start is at most "addr".
1.282 + // If "has_max_index" is true, "assumes "max_index" is the last valid one
1.283 + // in the array.
1.284 + inline HeapWord* block_at_or_preceding(const void* addr,
1.285 + bool has_max_index,
1.286 + size_t max_index) const;
1.287 +
1.288 + // "q" is a block boundary that is <= "addr"; "n" is the address of the
1.289 + // next block (or the end of the space.) Return the address of the
1.290 + // beginning of the block that contains "addr". Does so without side
1.291 + // effects (see, e.g., spec of block_start.)
1.292 + inline HeapWord*
1.293 + forward_to_block_containing_addr_const(HeapWord* q, HeapWord* n,
1.294 + const void* addr) const;
1.295 +
1.296 + // "q" is a block boundary that is <= "addr"; return the address of the
1.297 + // beginning of the block that contains "addr". May have side effects
1.298 + // on "this", by updating imprecise entries.
1.299 + inline HeapWord* forward_to_block_containing_addr(HeapWord* q,
1.300 + const void* addr);
1.301 +
1.302 + // "q" is a block boundary that is <= "addr"; "n" is the address of the
1.303 + // next block (or the end of the space.) Return the address of the
1.304 + // beginning of the block that contains "addr". May have side effects
1.305 + // on "this", by updating imprecise entries.
1.306 + HeapWord* forward_to_block_containing_addr_slow(HeapWord* q,
1.307 + HeapWord* n,
1.308 + const void* addr);
1.309 +
1.310 + // Requires that "*threshold_" be the first array entry boundary at or
1.311 + // above "blk_start", and that "*index_" be the corresponding array
1.312 + // index. If the block starts at or crosses "*threshold_", records
1.313 + // "blk_start" as the appropriate block start for the array index
1.314 + // starting at "*threshold_", and for any other indices crossed by the
1.315 + // block. Updates "*threshold_" and "*index_" to correspond to the first
1.316 + // index after the block end.
1.317 + void alloc_block_work2(HeapWord** threshold_, size_t* index_,
1.318 + HeapWord* blk_start, HeapWord* blk_end);
1.319 +
1.320 +public:
1.321 + // The space may not have it's bottom and top set yet, which is why the
1.322 + // region is passed as a parameter. If "init_to_zero" is true, the
1.323 + // elements of the array are initialized to zero. Otherwise, they are
1.324 + // initialized to point backwards to the beginning.
1.325 + G1BlockOffsetArray(G1BlockOffsetSharedArray* array, MemRegion mr,
1.326 + bool init_to_zero);
1.327 +
1.328 + // Note: this ought to be part of the constructor, but that would require
1.329 + // "this" to be passed as a parameter to a member constructor for
1.330 + // the containing concrete subtype of Space.
1.331 + // This would be legal C++, but MS VC++ doesn't allow it.
1.332 + void set_space(Space* sp);
1.333 +
1.334 + // Resets the covered region to the given "mr".
1.335 + void set_region(MemRegion mr);
1.336 +
1.337 + // Resets the covered region to one with the same _bottom as before but
1.338 + // the "new_word_size".
1.339 + void resize(size_t new_word_size);
1.340 +
1.341 + // These must be guaranteed to work properly (i.e., do nothing)
1.342 + // when "blk_start" ("blk" for second version) is "NULL".
1.343 + virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end);
1.344 + virtual void alloc_block(HeapWord* blk, size_t size) {
1.345 + alloc_block(blk, blk + size);
1.346 + }
1.347 +
1.348 + // The following methods are useful and optimized for a
1.349 + // general, non-contiguous space.
1.350 +
1.351 + // The given arguments are required to be the starts of adjacent ("blk1"
1.352 + // before "blk2") well-formed blocks covered by "this". After this call,
1.353 + // they should be considered to form one block.
1.354 + virtual void join_blocks(HeapWord* blk1, HeapWord* blk2);
1.355 +
1.356 + // Given a block [blk_start, blk_start + full_blk_size), and
1.357 + // a left_blk_size < full_blk_size, adjust the BOT to show two
1.358 + // blocks [blk_start, blk_start + left_blk_size) and
1.359 + // [blk_start + left_blk_size, blk_start + full_blk_size).
1.360 + // It is assumed (and verified in the non-product VM) that the
1.361 + // BOT was correct for the original block.
1.362 + void split_block(HeapWord* blk_start, size_t full_blk_size,
1.363 + size_t left_blk_size);
1.364 +
1.365 + // Adjust the BOT to show that it has a single block in the
1.366 + // range [blk_start, blk_start + size). All necessary BOT
1.367 + // cards are adjusted, but _unallocated_block isn't.
1.368 + void single_block(HeapWord* blk_start, HeapWord* blk_end);
1.369 + void single_block(HeapWord* blk, size_t size) {
1.370 + single_block(blk, blk + size);
1.371 + }
1.372 +
1.373 + // Adjust BOT to show that it has a block in the range
1.374 + // [blk_start, blk_start + size). Only the first card
1.375 + // of BOT is touched. It is assumed (and verified in the
1.376 + // non-product VM) that the remaining cards of the block
1.377 + // are correct.
1.378 + void mark_block(HeapWord* blk_start, HeapWord* blk_end);
1.379 + void mark_block(HeapWord* blk, size_t size) {
1.380 + mark_block(blk, blk + size);
1.381 + }
1.382 +
1.383 + // Adjust _unallocated_block to indicate that a particular
1.384 + // block has been newly allocated or freed. It is assumed (and
1.385 + // verified in the non-product VM) that the BOT is correct for
1.386 + // the given block.
1.387 + inline void allocated(HeapWord* blk_start, HeapWord* blk_end) {
1.388 + // Verify that the BOT shows [blk, blk + blk_size) to be one block.
1.389 + verify_single_block(blk_start, blk_end);
1.390 + if (BlockOffsetArrayUseUnallocatedBlock) {
1.391 + _unallocated_block = MAX2(_unallocated_block, blk_end);
1.392 + }
1.393 + }
1.394 +
1.395 + inline void allocated(HeapWord* blk, size_t size) {
1.396 + allocated(blk, blk + size);
1.397 + }
1.398 +
1.399 + inline void freed(HeapWord* blk_start, HeapWord* blk_end);
1.400 +
1.401 + inline void freed(HeapWord* blk, size_t size);
1.402 +
1.403 + virtual HeapWord* block_start_unsafe(const void* addr);
1.404 + virtual HeapWord* block_start_unsafe_const(const void* addr) const;
1.405 +
1.406 + // Requires "addr" to be the start of a card and returns the
1.407 + // start of the block that contains the given address.
1.408 + HeapWord* block_start_careful(const void* addr) const;
1.409 +
1.410 + // If true, initialize array slots with no allocated blocks to zero.
1.411 + // Otherwise, make them point back to the front.
1.412 + bool init_to_zero() { return _init_to_zero; }
1.413 +
1.414 + // Verification & debugging - ensure that the offset table reflects the fact
1.415 + // that the block [blk_start, blk_end) or [blk, blk + size) is a
1.416 + // single block of storage. NOTE: can;t const this because of
1.417 + // call to non-const do_block_internal() below.
1.418 + inline void verify_single_block(HeapWord* blk_start, HeapWord* blk_end) {
1.419 + if (VerifyBlockOffsetArray) {
1.420 + do_block_internal(blk_start, blk_end, Action_check);
1.421 + }
1.422 + }
1.423 +
1.424 + inline void verify_single_block(HeapWord* blk, size_t size) {
1.425 + verify_single_block(blk, blk + size);
1.426 + }
1.427 +
1.428 + // Verify that the given block is before _unallocated_block
1.429 + inline void verify_not_unallocated(HeapWord* blk_start,
1.430 + HeapWord* blk_end) const {
1.431 + if (BlockOffsetArrayUseUnallocatedBlock) {
1.432 + assert(blk_start < blk_end, "Block inconsistency?");
1.433 + assert(blk_end <= _unallocated_block, "_unallocated_block problem");
1.434 + }
1.435 + }
1.436 +
1.437 + inline void verify_not_unallocated(HeapWord* blk, size_t size) const {
1.438 + verify_not_unallocated(blk, blk + size);
1.439 + }
1.440 +
1.441 + void check_all_cards(size_t left_card, size_t right_card) const;
1.442 +};
1.443 +
1.444 +// A subtype of BlockOffsetArray that takes advantage of the fact
1.445 +// that its underlying space is a ContiguousSpace, so that its "active"
1.446 +// region can be more efficiently tracked (than for a non-contiguous space).
1.447 +class G1BlockOffsetArrayContigSpace: public G1BlockOffsetArray {
1.448 + friend class VMStructs;
1.449 +
1.450 + // allocation boundary at which offset array must be updated
1.451 + HeapWord* _next_offset_threshold;
1.452 + size_t _next_offset_index; // index corresponding to that boundary
1.453 +
1.454 + // Work function to be called when allocation start crosses the next
1.455 + // threshold in the contig space.
1.456 + void alloc_block_work1(HeapWord* blk_start, HeapWord* blk_end) {
1.457 + alloc_block_work2(&_next_offset_threshold, &_next_offset_index,
1.458 + blk_start, blk_end);
1.459 + }
1.460 +
1.461 +
1.462 + public:
1.463 + G1BlockOffsetArrayContigSpace(G1BlockOffsetSharedArray* array, MemRegion mr);
1.464 +
1.465 + // Initialize the threshold to reflect the first boundary after the
1.466 + // bottom of the covered region.
1.467 + HeapWord* initialize_threshold();
1.468 +
1.469 + // Zero out the entry for _bottom (offset will be zero).
1.470 + void zero_bottom_entry();
1.471 +
1.472 + // Return the next threshold, the point at which the table should be
1.473 + // updated.
1.474 + HeapWord* threshold() const { return _next_offset_threshold; }
1.475 +
1.476 + // These must be guaranteed to work properly (i.e., do nothing)
1.477 + // when "blk_start" ("blk" for second version) is "NULL". In this
1.478 + // implementation, that's true because NULL is represented as 0, and thus
1.479 + // never exceeds the "_next_offset_threshold".
1.480 + void alloc_block(HeapWord* blk_start, HeapWord* blk_end) {
1.481 + if (blk_end > _next_offset_threshold)
1.482 + alloc_block_work1(blk_start, blk_end);
1.483 + }
1.484 + void alloc_block(HeapWord* blk, size_t size) {
1.485 + alloc_block(blk, blk+size);
1.486 + }
1.487 +
1.488 + HeapWord* block_start_unsafe(const void* addr);
1.489 + HeapWord* block_start_unsafe_const(const void* addr) const;
1.490 +};
