1 /* 2 * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "memory/heap.hpp" 27 #include "oops/oop.inline.hpp" 28 #include "runtime/os.hpp" 29 #include "services/memTracker.hpp" 30 #include "utilities/align.hpp" 31 32 size_t CodeHeap::header_size() { 33 return sizeof(HeapBlock); 34 } 35 36 37 // Implementation of Heap 38 39 CodeHeap::CodeHeap(const char* name, const int code_blob_type) 40 : _code_blob_type(code_blob_type) { 41 _name = name; 42 _number_of_committed_segments = 0; 43 _number_of_reserved_segments = 0; 44 _segment_size = 0; 45 _log2_segment_size = 0; 46 _next_segment = 0; 47 _freelist = NULL; 48 _last_insert_point = NULL; 49 _freelist_segments = 0; 50 _freelist_length = 0; 51 _max_allocated_capacity = 0; 52 _blob_count = 0; 53 _nmethod_count = 0; 54 _adapter_count = 0; 55 _full_count = 0; 56 _fragmentation_count = 0; 57 } 58 59 // Dummy initialization of template array. 60 char CodeHeap::segmap_template[] = {0}; 61 62 // This template array is used to (re)initialize the segmap, 63 // replacing a 1..254 loop. 64 void CodeHeap::init_segmap_template() { 65 assert(free_sentinel == 255, "Segment map logic changed!"); 66 for (int i = 0; i <= free_sentinel; i++) { 67 segmap_template[i] = i; 68 } 69 } 70 71 // The segmap is marked free for that part of the heap 72 // which has not been allocated yet (beyond _next_segment). 73 // The range of segments to be marked is given by [beg..end). 74 // "Allocated" space in this context means there exists a 75 // HeapBlock or a FreeBlock describing this space. 76 // This method takes segment map indices as range boundaries 77 void CodeHeap::mark_segmap_as_free(size_t beg, size_t end) { 78 assert( beg < _number_of_committed_segments, "interval begin out of bounds"); 79 assert(beg < end && end <= _number_of_committed_segments, "interval end out of bounds"); 80 // Don't do unpredictable things in PRODUCT build 81 if (beg < end) { 82 // setup _segmap pointers for faster indexing 83 address p = (address)_segmap.low() + beg; 84 address q = (address)_segmap.low() + end; 85 // initialize interval 86 memset(p, free_sentinel, q-p); 87 } 88 } 89 90 // Don't get confused here. 91 // All existing blocks, no matter if they are used() or free(), 92 // have their segmap marked as used. This allows to find the 93 // block header (HeapBlock or FreeBlock) for any pointer 94 // within the allocated range (upper limit: _next_segment). 95 // This method takes segment map indices as range boundaries. 96 // The range of segments to be marked is given by [beg..end). 97 void CodeHeap::mark_segmap_as_used(size_t beg, size_t end, bool is_FreeBlock_join) { 98 assert( beg < _number_of_committed_segments, "interval begin out of bounds"); 99 assert(beg < end && end <= _number_of_committed_segments, "interval end out of bounds"); 100 // Don't do unpredictable things in PRODUCT build 101 if (beg < end) { 102 // setup _segmap pointers for faster indexing 103 address p = (address)_segmap.low() + beg; 104 address q = (address)_segmap.low() + end; 105 // initialize interval 106 // If we are joining two free blocks, the segmap range for each 107 // block is consistent. To create a consistent segmap range for 108 // the blocks combined, we have three choices: 109 // 1 - Do a full init from beg to end. Not very efficient because 110 // the segmap range for the left block is potentially initialized 111 // over and over again. 112 // 2 - Carry over the last segmap element value of the left block 113 // and initialize the segmap range of the right block starting 114 // with that value. Saves initializing the left block's segmap 115 // over and over again. Very efficient if FreeBlocks mostly 116 // are appended to the right. 117 // 3 - Take full advantage of the segmap being almost correct with 118 // the two blocks combined. Lets assume the left block consists 119 // of m segments. The the segmap looks like 120 // ... (m-2) (m-1) (m) 0 1 2 3 ... 121 // By substituting the '0' by '1', we create a valid, but 122 // suboptimal, segmap range covering the two blocks combined. 123 // We introduced an extra hop for the find_block_for() iteration. 124 // 125 // When this method is called with is_FreeBlock_join == true, the 126 // segmap index beg must select the first segment of the right block. 127 // Otherwise, it has to select the first segment of the left block. 128 // Variant 3 is used for all FreeBlock joins. 129 if (is_FreeBlock_join && (beg > 0)) { 130 #ifndef PRODUCT 131 FreeBlock* pBlock = (FreeBlock*)block_at(beg); 132 assert(beg + pBlock->length() == end, "Internal error: (%d - %d) != %d", (unsigned int)end, (unsigned int)beg, (unsigned int)(pBlock->length())); 133 assert(*p == 0, "Begin index does not select a block start segment, *p = %2.2x", *p); 134 #endif 135 // If possible, extend the previous hop. 136 if (*(p-1) < (free_sentinel-1)) { 137 *p = *(p-1) + 1; 138 } else { 139 *p = 1; 140 } 141 if (_fragmentation_count++ >= fragmentation_limit) { 142 defrag_segmap(true); 143 _fragmentation_count = 0; 144 } 145 } else { 146 size_t n_bulk = free_sentinel-1; // bulk processing uses template indices [1..254]. 147 // Use shortcut for blocks <= 255 segments. 148 // Special case bulk processing: [0..254]. 149 if ((end - beg) <= n_bulk) { 150 memcpy(p, &segmap_template[0], end - beg); 151 } else { 152 *p++ = 0; // block header marker 153 while (p < q) { 154 if ((p+n_bulk) <= q) { 155 memcpy(p, &segmap_template[1], n_bulk); 156 p += n_bulk; 157 } else { 158 memcpy(p, &segmap_template[1], q-p); 159 p = q; 160 } 161 } 162 } 163 } 164 } 165 } 166 167 void CodeHeap::invalidate(size_t beg, size_t end, size_t hdr_size) { 168 #ifndef PRODUCT 169 // Fill the given range with some bad value. 170 // length is expected to be in segment_size units. 171 // This prevents inadvertent execution of code leftover from previous use. 172 char* p = low_boundary() + segments_to_size(beg) + hdr_size; 173 memset(p, badCodeHeapNewVal, segments_to_size(end-beg)-hdr_size); 174 #endif 175 } 176 177 void CodeHeap::clear(size_t beg, size_t end) { 178 mark_segmap_as_free(beg, end); 179 invalidate(beg, end, 0); 180 } 181 182 void CodeHeap::clear() { 183 _next_segment = 0; 184 clear(_next_segment, _number_of_committed_segments); 185 } 186 187 188 static size_t align_to_page_size(size_t size) { 189 const size_t alignment = (size_t)os::vm_page_size(); 190 assert(is_power_of_2(alignment), "no kidding ???"); 191 return (size + alignment - 1) & ~(alignment - 1); 192 } 193 194 195 void CodeHeap::on_code_mapping(char* base, size_t size) { 196 #ifdef LINUX 197 extern void linux_wrap_code(char* base, size_t size); 198 linux_wrap_code(base, size); 199 #endif 200 } 201 202 203 bool CodeHeap::reserve(ReservedSpace rs, size_t committed_size, size_t segment_size) { 204 assert(rs.size() >= committed_size, "reserved < committed"); 205 assert(segment_size >= sizeof(FreeBlock), "segment size is too small"); 206 assert(is_power_of_2(segment_size), "segment_size must be a power of 2"); 207 assert_locked_or_safepoint(CodeCache_lock); 208 209 _segment_size = segment_size; 210 _log2_segment_size = exact_log2(segment_size); 211 212 // Reserve and initialize space for _memory. 213 size_t page_size = os::vm_page_size(); 214 if (os::can_execute_large_page_memory()) { 215 const size_t min_pages = 8; 216 page_size = MIN2(os::page_size_for_region_aligned(committed_size, min_pages), 217 os::page_size_for_region_aligned(rs.size(), min_pages)); 218 } 219 220 const size_t granularity = os::vm_allocation_granularity(); 221 const size_t c_size = align_up(committed_size, page_size); 222 223 os::trace_page_sizes(_name, committed_size, rs.size(), page_size, 224 rs.base(), rs.size()); 225 if (!_memory.initialize(rs, c_size)) { 226 return false; 227 } 228 229 on_code_mapping(_memory.low(), _memory.committed_size()); 230 _number_of_committed_segments = size_to_segments(_memory.committed_size()); 231 _number_of_reserved_segments = size_to_segments(_memory.reserved_size()); 232 assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking"); 233 const size_t reserved_segments_alignment = MAX2((size_t)os::vm_page_size(), granularity); 234 const size_t reserved_segments_size = align_up(_number_of_reserved_segments, reserved_segments_alignment); 235 const size_t committed_segments_size = align_to_page_size(_number_of_committed_segments); 236 237 // reserve space for _segmap 238 if (!_segmap.initialize(reserved_segments_size, committed_segments_size)) { 239 return false; 240 } 241 242 MemTracker::record_virtual_memory_type((address)_segmap.low_boundary(), mtCode); 243 244 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "could not commit enough space for segment map"); 245 assert(_segmap.reserved_size() >= (size_t) _number_of_reserved_segments , "could not reserve enough space for segment map"); 246 assert(_segmap.reserved_size() >= _segmap.committed_size() , "just checking"); 247 248 // initialize remaining instance variables, heap memory and segmap 249 clear(); 250 init_segmap_template(); 251 return true; 252 } 253 254 255 bool CodeHeap::expand_by(size_t size) { 256 assert_locked_or_safepoint(CodeCache_lock); 257 258 // expand _memory space 259 size_t dm = align_to_page_size(_memory.committed_size() + size) - _memory.committed_size(); 260 if (dm > 0) { 261 // Use at least the available uncommitted space if 'size' is larger 262 if (_memory.uncommitted_size() != 0 && dm > _memory.uncommitted_size()) { 263 dm = _memory.uncommitted_size(); 264 } 265 char* base = _memory.low() + _memory.committed_size(); 266 if (!_memory.expand_by(dm)) return false; 267 on_code_mapping(base, dm); 268 size_t i = _number_of_committed_segments; 269 _number_of_committed_segments = size_to_segments(_memory.committed_size()); 270 assert(_number_of_reserved_segments == size_to_segments(_memory.reserved_size()), "number of reserved segments should not change"); 271 assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking"); 272 // expand _segmap space 273 size_t ds = align_to_page_size(_number_of_committed_segments) - _segmap.committed_size(); 274 if ((ds > 0) && !_segmap.expand_by(ds)) { 275 return false; 276 } 277 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "just checking"); 278 // initialize additional space (heap memory and segmap) 279 clear(i, _number_of_committed_segments); 280 } 281 return true; 282 } 283 284 285 void* CodeHeap::allocate(size_t instance_size) { 286 size_t number_of_segments = size_to_segments(instance_size + header_size()); 287 assert(segments_to_size(number_of_segments) >= sizeof(FreeBlock), "not enough room for FreeList"); 288 assert_locked_or_safepoint(CodeCache_lock); 289 290 // First check if we can satisfy request from freelist 291 NOT_PRODUCT(verify()); 292 HeapBlock* block = search_freelist(number_of_segments); 293 NOT_PRODUCT(verify()); 294 295 if (block != NULL) { 296 assert(!block->free(), "must not be marked free"); 297 guarantee((char*) block >= _memory.low_boundary() && (char*) block < _memory.high(), 298 "The newly allocated block " INTPTR_FORMAT " is not within the heap " 299 "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT, 300 p2i(block), p2i(_memory.low_boundary()), p2i(_memory.high())); 301 _max_allocated_capacity = MAX2(_max_allocated_capacity, allocated_capacity()); 302 _blob_count++; 303 return block->allocated_space(); 304 } 305 306 // Ensure minimum size for allocation to the heap. 307 number_of_segments = MAX2((int)CodeCacheMinBlockLength, (int)number_of_segments); 308 309 if (_next_segment + number_of_segments <= _number_of_committed_segments) { 310 mark_segmap_as_used(_next_segment, _next_segment + number_of_segments, false); 311 block = block_at(_next_segment); 312 block->initialize(number_of_segments); 313 _next_segment += number_of_segments; 314 guarantee((char*) block >= _memory.low_boundary() && (char*) block < _memory.high(), 315 "The newly allocated block " INTPTR_FORMAT " is not within the heap " 316 "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT, 317 p2i(block), p2i(_memory.low_boundary()), p2i(_memory.high())); 318 _max_allocated_capacity = MAX2(_max_allocated_capacity, allocated_capacity()); 319 _blob_count++; 320 return block->allocated_space(); 321 } else { 322 return NULL; 323 } 324 } 325 326 // Split the given block into two at the given segment. 327 // This is helpful when a block was allocated too large 328 // to trim off the unused space at the end (interpreter). 329 // It also helps with splitting a large free block during allocation. 330 // Usage state (used or free) must be set by caller since 331 // we don't know if the resulting blocks will be used or free. 332 // split_at is the segment number (relative to segment_for(b)) 333 // where the split happens. The segment with relative 334 // number split_at is the first segment of the split-off block. 335 HeapBlock* CodeHeap::split_block(HeapBlock *b, size_t split_at) { 336 if (b == NULL) return NULL; 337 // After the split, both blocks must have a size of at least CodeCacheMinBlockLength 338 assert((split_at >= CodeCacheMinBlockLength) && (split_at + CodeCacheMinBlockLength <= b->length()), 339 "split position(%d) out of range [0..%d]", (int)split_at, (int)b->length()); 340 size_t split_segment = segment_for(b) + split_at; 341 size_t b_size = b->length(); 342 size_t newb_size = b_size - split_at; 343 344 HeapBlock* newb = block_at(split_segment); 345 newb->set_length(newb_size); 346 mark_segmap_as_used(segment_for(newb), segment_for(newb) + newb_size, false); 347 b->set_length(split_at); 348 return newb; 349 } 350 351 void CodeHeap::deallocate_tail(void* p, size_t used_size) { 352 assert(p == find_start(p), "illegal deallocation"); 353 assert_locked_or_safepoint(CodeCache_lock); 354 355 // Find start of HeapBlock 356 HeapBlock* b = (((HeapBlock *)p) - 1); 357 assert(b->allocated_space() == p, "sanity check"); 358 359 size_t actual_number_of_segments = b->length(); 360 size_t used_number_of_segments = size_to_segments(used_size + header_size()); 361 size_t unused_number_of_segments = actual_number_of_segments - used_number_of_segments; 362 guarantee(used_number_of_segments <= actual_number_of_segments, "Must be!"); 363 364 HeapBlock* f = split_block(b, used_number_of_segments); 365 add_to_freelist(f); 366 NOT_PRODUCT(verify()); 367 } 368 369 void CodeHeap::deallocate(void* p) { 370 assert(p == find_start(p), "illegal deallocation"); 371 assert_locked_or_safepoint(CodeCache_lock); 372 373 // Find start of HeapBlock 374 HeapBlock* b = (((HeapBlock *)p) - 1); 375 assert(b->allocated_space() == p, "sanity check"); 376 guarantee((char*) b >= _memory.low_boundary() && (char*) b < _memory.high(), 377 "The block to be deallocated " INTPTR_FORMAT " is not within the heap " 378 "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT, 379 p2i(b), p2i(_memory.low_boundary()), p2i(_memory.high())); 380 add_to_freelist(b); 381 NOT_PRODUCT(verify()); 382 } 383 384 /** 385 * The segment map is used to quickly find the the start (header) of a 386 * code block (e.g. nmethod) when only a pointer to a location inside the 387 * code block is known. This works as follows: 388 * - The storage reserved for the code heap is divided into 'segments'. 389 * - The size of a segment is determined by -XX:CodeCacheSegmentSize=<#bytes>. 390 * - The size must be a power of two to allow the use of shift operations 391 * to quickly convert between segment index and segment address. 392 * - Segment start addresses should be aligned to be multiples of CodeCacheSegmentSize. 393 * - It seems beneficial for CodeCacheSegmentSize to be equal to os::page_size(). 394 * - Allocation in the code cache can only happen at segment start addresses. 395 * - Allocation in the code cache is in units of CodeCacheSegmentSize. 396 * - A pointer in the code cache can be mapped to a segment by calling 397 * segment_for(addr). 398 * - The segment map is a byte array where array element [i] is related 399 * to the i-th segment in the code heap. 400 * - Each time memory is allocated/deallocated from the code cache, 401 * the segment map is updated accordingly. 402 * Note: deallocation does not cause the memory to become "free", as 403 * indicated by the segment map state "free_sentinel". Deallocation 404 * just changes the block state from "used" to "free". 405 * - Elements of the segment map (byte) array are interpreted 406 * as unsigned integer. 407 * - Element values normally identify an offset backwards (in segment 408 * size units) from the associated segment towards the start of 409 * the block. 410 * - Some values have a special meaning: 411 * 0 - This segment is the start of a block (HeapBlock or FreeBlock). 412 * 255 - The free_sentinel value. This is a free segment, i.e. it is 413 * not yet allocated and thus does not belong to any block. 414 * - The value of the current element has to be subtracted from the 415 * current index to get closer to the start. 416 * - If the value of the then current element is zero, the block start 417 * segment is found and iteration stops. Otherwise, start over with the 418 * previous step. 419 * 420 * The following example illustrates a possible state of code cache 421 * and the segment map: (seg -> segment, nm ->nmethod) 422 * 423 * code cache segmap 424 * ----------- --------- 425 * seg 1 | nm 1 | -> | 0 | 426 * seg 2 | nm 1 | -> | 1 | 427 * ... | nm 1 | -> | .. | 428 * seg m-1 | nm 1 | -> | m-1 | 429 * seg m | nm 2 | -> | 0 | 430 * seg m+1 | nm 2 | -> | 1 | 431 * ... | nm 2 | -> | 2 | 432 * ... | nm 2 | -> | .. | 433 * ... | nm 2 | -> | 0xFE | (free_sentinel-1) 434 * ... | nm 2 | -> | 1 | 435 * seg m+n | nm 2 | -> | 2 | 436 * ... | nm 2 | -> | | 437 * 438 * How to read: 439 * A value of '0' in the segmap indicates that this segment contains the 440 * beginning of a CodeHeap block. Let's walk through a simple example: 441 * 442 * We want to find the start of the block that contains nm 1, and we are 443 * given a pointer that points into segment m-2. We then read the value 444 * of segmap[m-2]. The value is an offset that points to the segment 445 * which contains the start of the block. 446 * 447 * Another example: We want to locate the start of nm 2, and we happen to 448 * get a pointer that points into seg m+n. We first read seg[n+m], which 449 * returns '2'. So we have to update our segment map index (ix -= segmap[n+m]) 450 * and start over. 451 */ 452 453 // Find block which contains the passed pointer, 454 // regardless of the block being used or free. 455 // NULL is returned if anything invalid is detected. 456 void* CodeHeap::find_block_for(void* p) const { 457 // Check the pointer to be in committed range. 458 if (!contains(p)) { 459 return NULL; 460 } 461 462 address seg_map = (address)_segmap.low(); 463 size_t seg_idx = segment_for(p); 464 465 // This may happen in special cases. Just ignore. 466 // Example: PPC ICache stub generation. 467 if (is_segment_unused(seg_map[seg_idx])) { 468 return NULL; 469 } 470 471 // Iterate the segment map chain to find the start of the block. 472 while (seg_map[seg_idx] > 0) { 473 // Don't check each segment index to refer to a used segment. 474 // This method is called extremely often. Therefore, any checking 475 // has a significant impact on performance. Rely on CodeHeap::verify() 476 // to do the job on request. 477 seg_idx -= (int)seg_map[seg_idx]; 478 } 479 480 return address_for(seg_idx); 481 } 482 483 // Find block which contains the passed pointer. 484 // The block must be used, i.e. must not be a FreeBlock. 485 // Return a pointer that points past the block header. 486 void* CodeHeap::find_start(void* p) const { 487 HeapBlock* h = (HeapBlock*)find_block_for(p); 488 return ((h == NULL) || h->free()) ? NULL : h->allocated_space(); 489 } 490 491 // Find block which contains the passed pointer. 492 // Same as find_start(p), but with additional safety net. 493 CodeBlob* CodeHeap::find_blob_unsafe(void* start) const { 494 CodeBlob* result = (CodeBlob*)CodeHeap::find_start(start); 495 return (result != NULL && result->blob_contains((address)start)) ? result : NULL; 496 } 497 498 size_t CodeHeap::alignment_unit() const { 499 // this will be a power of two 500 return _segment_size; 501 } 502 503 504 size_t CodeHeap::alignment_offset() const { 505 // The lowest address in any allocated block will be 506 // equal to alignment_offset (mod alignment_unit). 507 return sizeof(HeapBlock) & (_segment_size - 1); 508 } 509 510 // Returns the current block if available and used. 511 // If not, it returns the subsequent block (if available), NULL otherwise. 512 // Free blocks are merged, therefore there is at most one free block 513 // between two used ones. As a result, the subsequent block (if available) is 514 // guaranteed to be used. 515 // The returned pointer points past the block header. 516 void* CodeHeap::next_used(HeapBlock* b) const { 517 if (b != NULL && b->free()) b = next_block(b); 518 assert(b == NULL || !b->free(), "must be in use or at end of heap"); 519 return (b == NULL) ? NULL : b->allocated_space(); 520 } 521 522 // Returns the first used HeapBlock 523 // The returned pointer points to the block header. 524 HeapBlock* CodeHeap::first_block() const { 525 if (_next_segment > 0) 526 return block_at(0); 527 return NULL; 528 } 529 530 // The returned pointer points to the block header. 531 HeapBlock* CodeHeap::block_start(void* q) const { 532 HeapBlock* b = (HeapBlock*)find_start(q); 533 if (b == NULL) return NULL; 534 return b - 1; 535 } 536 537 // Returns the next Heap block. 538 // The returned pointer points to the block header. 539 HeapBlock* CodeHeap::next_block(HeapBlock *b) const { 540 if (b == NULL) return NULL; 541 size_t i = segment_for(b) + b->length(); 542 if (i < _next_segment) 543 return block_at(i); 544 return NULL; 545 } 546 547 548 // Returns current capacity 549 size_t CodeHeap::capacity() const { 550 return _memory.committed_size(); 551 } 552 553 size_t CodeHeap::max_capacity() const { 554 return _memory.reserved_size(); 555 } 556 557 int CodeHeap::allocated_segments() const { 558 return (int)_next_segment; 559 } 560 561 size_t CodeHeap::allocated_capacity() const { 562 // size of used heap - size on freelist 563 return segments_to_size(_next_segment - _freelist_segments); 564 } 565 566 // Returns size of the unallocated heap block 567 size_t CodeHeap::heap_unallocated_capacity() const { 568 // Total number of segments - number currently used 569 return segments_to_size(_number_of_reserved_segments - _next_segment); 570 } 571 572 // Free list management 573 574 FreeBlock* CodeHeap::following_block(FreeBlock *b) { 575 return (FreeBlock*)(((address)b) + _segment_size * b->length()); 576 } 577 578 // Inserts block b after a 579 void CodeHeap::insert_after(FreeBlock* a, FreeBlock* b) { 580 assert(a != NULL && b != NULL, "must be real pointers"); 581 582 // Link b into the list after a 583 b->set_link(a->link()); 584 a->set_link(b); 585 586 // See if we can merge blocks 587 merge_right(b); // Try to make b bigger 588 merge_right(a); // Try to make a include b 589 } 590 591 // Try to merge this block with the following block 592 bool CodeHeap::merge_right(FreeBlock* a) { 593 assert(a->free(), "must be a free block"); 594 if (following_block(a) == a->link()) { 595 assert(a->link() != NULL && a->link()->free(), "must be free too"); 596 597 // Remember linked (following) block. invalidate should only zap header of this block. 598 size_t follower = segment_for(a->link()); 599 // Merge block a to include the following block. 600 a->set_length(a->length() + a->link()->length()); 601 a->set_link(a->link()->link()); 602 603 // Update the segment map and invalidate block contents. 604 mark_segmap_as_used(follower, segment_for(a) + a->length(), true); 605 // Block contents has already been invalidated by add_to_freelist. 606 // What's left is the header of the following block which now is 607 // in the middle of the merged block. Just zap one segment. 608 invalidate(follower, follower + 1, 0); 609 610 _freelist_length--; 611 return true; 612 } 613 return false; 614 } 615 616 617 void CodeHeap::add_to_freelist(HeapBlock* a) { 618 FreeBlock* b = (FreeBlock*)a; 619 size_t bseg = segment_for(b); 620 _freelist_length++; 621 622 _blob_count--; 623 assert(_blob_count >= 0, "sanity"); 624 625 assert(b != _freelist, "cannot be removed twice"); 626 627 // Mark as free and update free space count 628 _freelist_segments += b->length(); 629 b->set_free(); 630 invalidate(bseg, bseg + b->length(), sizeof(FreeBlock)); 631 632 // First element in list? 633 if (_freelist == NULL) { 634 b->set_link(NULL); 635 _freelist = b; 636 return; 637 } 638 639 // Since the freelist is ordered (smaller addresses -> larger addresses) and the 640 // element we want to insert into the freelist has a smaller address than the first 641 // element, we can simply add 'b' as the first element and we are done. 642 if (b < _freelist) { 643 // Insert first in list 644 b->set_link(_freelist); 645 _freelist = b; 646 merge_right(_freelist); 647 return; 648 } 649 650 // Scan for right place to put into list. 651 // List is sorted by increasing addresses. 652 FreeBlock* prev = _freelist; 653 FreeBlock* cur = _freelist->link(); 654 if ((_freelist_length > freelist_limit) && (_last_insert_point != NULL)) { 655 _last_insert_point = (FreeBlock*)find_block_for(_last_insert_point); 656 if ((_last_insert_point != NULL) && _last_insert_point->free() && (_last_insert_point < b)) { 657 prev = _last_insert_point; 658 cur = prev->link(); 659 } 660 } 661 while(cur != NULL && cur < b) { 662 assert(prev < cur, "Freelist must be ordered"); 663 prev = cur; 664 cur = cur->link(); 665 } 666 assert((prev < b) && (cur == NULL || b < cur), "free-list must be ordered"); 667 insert_after(prev, b); 668 _last_insert_point = prev; 669 } 670 671 /** 672 * Search freelist for an entry on the list with the best fit. 673 * @return NULL, if no one was found 674 */ 675 HeapBlock* CodeHeap::search_freelist(size_t length) { 676 FreeBlock* found_block = NULL; 677 FreeBlock* found_prev = NULL; 678 size_t found_length = _next_segment; // max it out to begin with 679 680 HeapBlock* res = NULL; 681 FreeBlock* prev = NULL; 682 FreeBlock* cur = _freelist; 683 684 length = length < CodeCacheMinBlockLength ? CodeCacheMinBlockLength : length; 685 686 // Search for best-fitting block 687 while(cur != NULL) { 688 size_t cur_length = cur->length(); 689 if (cur_length == length) { 690 // We have a perfect fit 691 found_block = cur; 692 found_prev = prev; 693 found_length = cur_length; 694 break; 695 } else if ((cur_length > length) && (cur_length < found_length)) { 696 // This is a new, closer fit. Remember block, its previous element, and its length 697 found_block = cur; 698 found_prev = prev; 699 found_length = cur_length; 700 } 701 // Next element in list 702 prev = cur; 703 cur = cur->link(); 704 } 705 706 if (found_block == NULL) { 707 // None found 708 return NULL; 709 } 710 711 // Exact (or at least good enough) fit. Remove from list. 712 // Don't leave anything on the freelist smaller than CodeCacheMinBlockLength. 713 if (found_length - length < CodeCacheMinBlockLength) { 714 _freelist_length--; 715 length = found_length; 716 if (found_prev == NULL) { 717 assert(_freelist == found_block, "sanity check"); 718 _freelist = _freelist->link(); 719 } else { 720 assert((found_prev->link() == found_block), "sanity check"); 721 // Unmap element 722 found_prev->set_link(found_block->link()); 723 } 724 res = (HeapBlock*)found_block; 725 // sizeof(HeapBlock) < sizeof(FreeBlock). 726 // Invalidate the additional space that FreeBlock occupies. 727 // The rest of the block should already be invalidated. 728 // This is necessary due to a dubious assert in nmethod.cpp(PcDescCache::reset_to()). 729 // Can't use invalidate() here because it works on segment_size units (too coarse). 730 DEBUG_ONLY(memset((void*)res->allocated_space(), badCodeHeapNewVal, sizeof(FreeBlock) - sizeof(HeapBlock))); 731 } else { 732 // Truncate the free block and return the truncated part 733 // as new HeapBlock. The remaining free block does not 734 // need to be updated, except for it's length. Truncating 735 // the segment map does not invalidate the leading part. 736 res = split_block(found_block, found_length - length); 737 } 738 739 res->set_used(); 740 _freelist_segments -= length; 741 return res; 742 } 743 744 int CodeHeap::defrag_segmap(bool do_defrag) { 745 int extra_hops_used = 0; 746 int extra_hops_free = 0; 747 int blocks_used = 0; 748 int blocks_free = 0; 749 for(HeapBlock* h = first_block(); h != NULL; h = next_block(h)) { 750 size_t beg = segment_for(h); 751 size_t end = segment_for(h) + h->length(); 752 int extra_hops = segmap_hops(beg, end); 753 if (h->free()) { 754 extra_hops_free += extra_hops; 755 blocks_free++; 756 } else { 757 extra_hops_used += extra_hops; 758 blocks_used++; 759 } 760 if (do_defrag && (extra_hops > 0)) { 761 mark_segmap_as_used(beg, end, false); 762 } 763 } 764 return extra_hops_used + extra_hops_free; 765 } 766 767 // Count the hops required to get from the last segment of a 768 // heap block to the block header segment. For the optimal case, 769 // #hops = ((#segments-1)+(free_sentinel-2))/(free_sentinel-1) 770 // The range of segments to be checked is given by [beg..end). 771 // Return the number of extra hops required. There may be extra hops 772 // due to the is_FreeBlock_join optimization in mark_segmap_as_used(). 773 int CodeHeap::segmap_hops(size_t beg, size_t end) { 774 if (beg < end) { 775 // setup _segmap pointers for faster indexing 776 address p = (address)_segmap.low() + beg; 777 int hops_expected = (int)(((end-beg-1)+(free_sentinel-2))/(free_sentinel-1)); 778 int nhops = 0; 779 size_t ix = end-beg-1; 780 while (p[ix] > 0) { 781 ix -= p[ix]; 782 nhops++; 783 } 784 return (nhops > hops_expected) ? nhops - hops_expected : 0; 785 } 786 return 0; 787 } 788 789 //---------------------------------------------------------------------------- 790 // Non-product code 791 792 #ifndef PRODUCT 793 794 void CodeHeap::print() { 795 tty->print_cr("The Heap"); 796 } 797 798 void CodeHeap::verify() { 799 if (VerifyCodeCache) { 800 assert_locked_or_safepoint(CodeCache_lock); 801 size_t len = 0; 802 int count = 0; 803 for(FreeBlock* b = _freelist; b != NULL; b = b->link()) { 804 len += b->length(); 805 count++; 806 // Check if we have merged all free blocks 807 assert(merge_right(b) == false, "Missed merging opportunity"); 808 } 809 // Verify that freelist contains the right amount of free space 810 assert(len == _freelist_segments, "wrong freelist"); 811 812 for(HeapBlock* h = first_block(); h != NULL; h = next_block(h)) { 813 if (h->free()) count--; 814 } 815 // Verify that the freelist contains the same number of blocks 816 // than free blocks found on the full list. 817 assert(count == 0, "missing free blocks"); 818 819 //---< all free block memory must have been invalidated >--- 820 for(FreeBlock* b = _freelist; b != NULL; b = b->link()) { 821 for (char* c = (char*)b + sizeof(FreeBlock); c < (char*)b + segments_to_size(b->length()); c++) { 822 assert(*c == (char)badCodeHeapNewVal, "FreeBlock@" PTR_FORMAT "(" PTR_FORMAT ") not invalidated @byte %d", p2i(b), b->length(), (int)(c - (char*)b)); 823 } 824 } 825 826 address seg_map = (address)_segmap.low(); 827 size_t nseg = 0; 828 int extra_hops = 0; 829 count = 0; 830 for(HeapBlock* b = first_block(); b != NULL; b = next_block(b)) { 831 size_t seg1 = segment_for(b); 832 size_t segn = seg1 + b->length(); 833 extra_hops += segmap_hops(seg1, segn); 834 count++; 835 for (size_t i = seg1; i < segn; i++) { 836 nseg++; 837 //---< Verify segment map marking >--- 838 // All allocated segments, no matter if in a free or used block, 839 // must be marked "in use". 840 assert(!is_segment_unused(seg_map[i]), "CodeHeap: unused segment. seg_map[%d]([%d..%d]) = %d, %s block", (int)i, (int)seg1, (int)segn, seg_map[i], b->free()? "free":"used"); 841 assert((unsigned char)seg_map[i] < free_sentinel, "CodeHeap: seg_map[%d]([%d..%d]) = %d (out of range)", (int)i, (int)seg1, (int)segn, seg_map[i]); 842 } 843 } 844 assert(nseg == _next_segment, "CodeHeap: segment count mismatch. found %d, expected %d.", (int)nseg, (int)_next_segment); 845 assert((count == 0) || (extra_hops < (16 + 2*count)), "CodeHeap: many extra hops due to optimization. blocks: %d, extra hops: %d.", count, extra_hops); 846 847 // Verify that the number of free blocks is not out of hand. 848 static int free_block_threshold = 10000; 849 if (count > free_block_threshold) { 850 warning("CodeHeap: # of free blocks > %d", free_block_threshold); 851 // Double the warning limit 852 free_block_threshold *= 2; 853 } 854 } 855 } 856 857 #endif