1 /* 2 * Copyright (c) 1997, 2013, 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 31 size_t CodeHeap::header_size() { 32 return sizeof(HeapBlock); 33 } 34 35 36 // Implementation of Heap 37 38 CodeHeap::CodeHeap(const char* name, const int code_blob_type) 39 : _code_blob_type(code_blob_type) { 40 _name = name; 41 _number_of_committed_segments = 0; 42 _number_of_reserved_segments = 0; 43 _segment_size = 0; 44 _log2_segment_size = 0; 45 _next_segment = 0; 46 _freelist = NULL; 47 _freelist_segments = 0; 48 _freelist_length = 0; 49 _max_allocated_capacity = 0; 50 _was_full = false; 51 } 52 53 54 void CodeHeap::mark_segmap_as_free(size_t beg, size_t end) { 55 assert(0 <= beg && beg < _number_of_committed_segments, "interval begin out of bounds"); 56 assert(beg < end && end <= _number_of_committed_segments, "interval end out of bounds"); 57 // setup _segmap pointers for faster indexing 58 address p = (address)_segmap.low() + beg; 59 address q = (address)_segmap.low() + end; 60 // initialize interval 61 while (p < q) *p++ = free_sentinel; 62 } 63 64 65 void CodeHeap::mark_segmap_as_used(size_t beg, size_t end) { 66 assert(0 <= beg && beg < _number_of_committed_segments, "interval begin out of bounds"); 67 assert(beg < end && end <= _number_of_committed_segments, "interval end out of bounds"); 68 // setup _segmap pointers for faster indexing 69 address p = (address)_segmap.low() + beg; 70 address q = (address)_segmap.low() + end; 71 // initialize interval 72 int i = 0; 73 while (p < q) { 74 *p++ = i++; 75 if (i == free_sentinel) i = 1; 76 } 77 } 78 79 80 static size_t align_to_page_size(size_t size) { 81 const size_t alignment = (size_t)os::vm_page_size(); 82 assert(is_power_of_2(alignment), "no kidding ???"); 83 return (size + alignment - 1) & ~(alignment - 1); 84 } 85 86 87 void CodeHeap::on_code_mapping(char* base, size_t size) { 88 #ifdef LINUX 89 extern void linux_wrap_code(char* base, size_t size); 90 linux_wrap_code(base, size); 91 #endif 92 } 93 94 95 bool CodeHeap::reserve(ReservedSpace rs, size_t committed_size, size_t segment_size) { 96 assert(rs.size() >= committed_size, "reserved < committed"); 97 assert(segment_size >= sizeof(FreeBlock), "segment size is too small"); 98 assert(is_power_of_2(segment_size), "segment_size must be a power of 2"); 99 100 _segment_size = segment_size; 101 _log2_segment_size = exact_log2(segment_size); 102 103 // Reserve and initialize space for _memory. 104 size_t page_size = os::vm_page_size(); 105 if (os::can_execute_large_page_memory()) { 106 const size_t min_pages = 8; 107 page_size = MIN2(os::page_size_for_region(committed_size, min_pages), 108 os::page_size_for_region(rs.size(), min_pages)); 109 } 110 111 const size_t granularity = os::vm_allocation_granularity(); 112 const size_t c_size = align_size_up(committed_size, page_size); 113 114 os::trace_page_sizes(_name, committed_size, rs.size(), page_size, 115 rs.base(), rs.size()); 116 if (!_memory.initialize(rs, c_size)) { 117 return false; 118 } 119 120 on_code_mapping(_memory.low(), _memory.committed_size()); 121 _number_of_committed_segments = size_to_segments(_memory.committed_size()); 122 _number_of_reserved_segments = size_to_segments(_memory.reserved_size()); 123 assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking"); 124 const size_t reserved_segments_alignment = MAX2((size_t)os::vm_page_size(), granularity); 125 const size_t reserved_segments_size = align_size_up(_number_of_reserved_segments, reserved_segments_alignment); 126 const size_t committed_segments_size = align_to_page_size(_number_of_committed_segments); 127 128 // reserve space for _segmap 129 if (!_segmap.initialize(reserved_segments_size, committed_segments_size)) { 130 return false; 131 } 132 133 MemTracker::record_virtual_memory_type((address)_segmap.low_boundary(), mtCode); 134 135 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "could not commit enough space for segment map"); 136 assert(_segmap.reserved_size() >= (size_t) _number_of_reserved_segments , "could not reserve enough space for segment map"); 137 assert(_segmap.reserved_size() >= _segmap.committed_size() , "just checking"); 138 139 // initialize remaining instance variables 140 clear(); 141 return true; 142 } 143 144 145 bool CodeHeap::expand_by(size_t size) { 146 // expand _memory space 147 size_t dm = align_to_page_size(_memory.committed_size() + size) - _memory.committed_size(); 148 if (dm > 0) { 149 char* base = _memory.low() + _memory.committed_size(); 150 if (!_memory.expand_by(dm)) return false; 151 on_code_mapping(base, dm); 152 size_t i = _number_of_committed_segments; 153 _number_of_committed_segments = size_to_segments(_memory.committed_size()); 154 assert(_number_of_reserved_segments == size_to_segments(_memory.reserved_size()), "number of reserved segments should not change"); 155 assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking"); 156 // expand _segmap space 157 size_t ds = align_to_page_size(_number_of_committed_segments) - _segmap.committed_size(); 158 if ((ds > 0) && !_segmap.expand_by(ds)) { 159 return false; 160 } 161 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "just checking"); 162 // initialize additional segmap entries 163 mark_segmap_as_free(i, _number_of_committed_segments); 164 } 165 return true; 166 } 167 168 void CodeHeap::clear() { 169 _next_segment = 0; 170 mark_segmap_as_free(0, _number_of_committed_segments); 171 } 172 173 174 void* CodeHeap::allocate(size_t instance_size, bool is_critical) { 175 size_t number_of_segments = size_to_segments(instance_size + header_size()); 176 assert(segments_to_size(number_of_segments) >= sizeof(FreeBlock), "not enough room for FreeList"); 177 178 // First check if we can satisfy request from freelist 179 NOT_PRODUCT(verify()); 180 HeapBlock* block = search_freelist(number_of_segments, is_critical); 181 NOT_PRODUCT(verify()); 182 183 if (block != NULL) { 184 assert(block->length() >= number_of_segments && block->length() < number_of_segments + CodeCacheMinBlockLength, "sanity check"); 185 assert(!block->free(), "must be marked free"); 186 DEBUG_ONLY(memset((void*)block->allocated_space(), badCodeHeapNewVal, instance_size)); 187 _max_allocated_capacity = MAX2(_max_allocated_capacity, allocated_capacity()); 188 return block->allocated_space(); 189 } 190 191 // Ensure minimum size for allocation to the heap. 192 number_of_segments = MAX2((int)CodeCacheMinBlockLength, (int)number_of_segments); 193 194 if (!is_critical) { 195 // Make sure the allocation fits in the unallocated heap without using 196 // the CodeCacheMimimumFreeSpace that is reserved for critical allocations. 197 if (segments_to_size(number_of_segments) > (heap_unallocated_capacity() - CodeCacheMinimumFreeSpace)) { 198 // Fail allocation 199 return NULL; 200 } 201 } 202 203 if (_next_segment + number_of_segments <= _number_of_committed_segments) { 204 mark_segmap_as_used(_next_segment, _next_segment + number_of_segments); 205 HeapBlock* b = block_at(_next_segment); 206 b->initialize(number_of_segments); 207 _next_segment += number_of_segments; 208 DEBUG_ONLY(memset((void *)b->allocated_space(), badCodeHeapNewVal, instance_size)); 209 _max_allocated_capacity = MAX2(_max_allocated_capacity, allocated_capacity()); 210 return b->allocated_space(); 211 } else { 212 return NULL; 213 } 214 } 215 216 217 void CodeHeap::deallocate(void* p) { 218 assert(p == find_start(p), "illegal deallocation"); 219 // Find start of HeapBlock 220 HeapBlock* b = (((HeapBlock *)p) - 1); 221 assert(b->allocated_space() == p, "sanity check"); 222 DEBUG_ONLY(memset((void *)b->allocated_space(), badCodeHeapFreeVal, 223 segments_to_size(b->length()) - sizeof(HeapBlock))); 224 add_to_freelist(b); 225 NOT_PRODUCT(verify()); 226 } 227 228 /** 229 * Uses segment map to find the the start (header) of a nmethod. This works as follows: 230 * The memory of the code cache is divided into 'segments'. The size of a segment is 231 * determined by -XX:CodeCacheSegmentSize=XX. Allocation in the code cache can only 232 * happen at segment boundaries. A pointer in the code cache can be mapped to a segment 233 * by calling segment_for(addr). Each time memory is requested from the code cache, 234 * the segmap is updated accordingly. See the following example, which illustrates the 235 * state of code cache and the segment map: (seg -> segment, nm ->nmethod) 236 * 237 * code cache segmap 238 * ----------- --------- 239 * seg 1 | nm 1 | -> | 0 | 240 * seg 2 | nm 1 | -> | 1 | 241 * ... | nm 1 | -> | .. | 242 * seg m | nm 2 | -> | 0 | 243 * seg m+1 | nm 2 | -> | 1 | 244 * ... | nm 2 | -> | 2 | 245 * ... | nm 2 | -> | .. | 246 * ... | nm 2 | -> | 0xFE | 247 * seg m+n | nm 2 | -> | 1 | 248 * ... | nm 2 | -> | | 249 * 250 * A value of '0' in the segmap indicates that this segment contains the beginning of 251 * an nmethod. Let's walk through a simple example: If we want to find the start of 252 * an nmethod that falls into seg 2, we read the value of the segmap[2]. The value 253 * is an offset that points to the segment that contains the start of the nmethod. 254 * Another example: If we want to get the start of nm 2, and we happen to get a pointer 255 * that points to seg m+n, we first read seg[n+m], which returns '1'. So we have to 256 * do one more read of the segmap[m+n-1] to finally get the segment header. 257 */ 258 void* CodeHeap::find_start(void* p) const { 259 if (!contains(p)) { 260 return NULL; 261 } 262 size_t seg_idx = segment_for(p); 263 address seg_map = (address)_segmap.low(); 264 if (is_segment_unused(seg_map[seg_idx])) { 265 return NULL; 266 } 267 while (seg_map[seg_idx] > 0) { 268 seg_idx -= (int)seg_map[seg_idx]; 269 } 270 271 HeapBlock* h = block_at(seg_idx); 272 if (h->free()) { 273 return NULL; 274 } 275 return h->allocated_space(); 276 } 277 278 279 size_t CodeHeap::alignment_unit() const { 280 // this will be a power of two 281 return _segment_size; 282 } 283 284 285 size_t CodeHeap::alignment_offset() const { 286 // The lowest address in any allocated block will be 287 // equal to alignment_offset (mod alignment_unit). 288 return sizeof(HeapBlock) & (_segment_size - 1); 289 } 290 291 // Finds the next free heapblock. If the current one is free, that it returned 292 void* CodeHeap::next_free(HeapBlock* b) const { 293 // Since free blocks are merged, there is max. on free block 294 // between two used ones 295 if (b != NULL && b->free()) b = next_block(b); 296 assert(b == NULL || !b->free(), "must be in use or at end of heap"); 297 return (b == NULL) ? NULL : b->allocated_space(); 298 } 299 300 // Returns the first used HeapBlock 301 HeapBlock* CodeHeap::first_block() const { 302 if (_next_segment > 0) 303 return block_at(0); 304 return NULL; 305 } 306 307 HeapBlock* CodeHeap::block_start(void* q) const { 308 HeapBlock* b = (HeapBlock*)find_start(q); 309 if (b == NULL) return NULL; 310 return b - 1; 311 } 312 313 // Returns the next Heap block an offset into one 314 HeapBlock* CodeHeap::next_block(HeapBlock *b) const { 315 if (b == NULL) return NULL; 316 size_t i = segment_for(b) + b->length(); 317 if (i < _next_segment) 318 return block_at(i); 319 return NULL; 320 } 321 322 323 // Returns current capacity 324 size_t CodeHeap::capacity() const { 325 return _memory.committed_size(); 326 } 327 328 size_t CodeHeap::max_capacity() const { 329 return _memory.reserved_size(); 330 } 331 332 int CodeHeap::allocated_segments() const { 333 return (int)_next_segment; 334 } 335 336 size_t CodeHeap::allocated_capacity() const { 337 // size of used heap - size on freelist 338 return segments_to_size(_next_segment - _freelist_segments); 339 } 340 341 // Returns size of the unallocated heap block 342 size_t CodeHeap::heap_unallocated_capacity() const { 343 // Total number of segments - number currently used 344 return segments_to_size(_number_of_reserved_segments - _next_segment); 345 } 346 347 // Free list management 348 349 FreeBlock* CodeHeap::following_block(FreeBlock *b) { 350 return (FreeBlock*)(((address)b) + _segment_size * b->length()); 351 } 352 353 // Inserts block b after a 354 void CodeHeap::insert_after(FreeBlock* a, FreeBlock* b) { 355 assert(a != NULL && b != NULL, "must be real pointers"); 356 357 // Link b into the list after a 358 b->set_link(a->link()); 359 a->set_link(b); 360 361 // See if we can merge blocks 362 merge_right(b); // Try to make b bigger 363 merge_right(a); // Try to make a include b 364 } 365 366 // Try to merge this block with the following block 367 bool CodeHeap::merge_right(FreeBlock* a) { 368 assert(a->free(), "must be a free block"); 369 if (following_block(a) == a->link()) { 370 assert(a->link() != NULL && a->link()->free(), "must be free too"); 371 // Update block a to include the following block 372 a->set_length(a->length() + a->link()->length()); 373 a->set_link(a->link()->link()); 374 // Update find_start map 375 size_t beg = segment_for(a); 376 mark_segmap_as_used(beg, beg + a->length()); 377 _freelist_length--; 378 return true; 379 } 380 return false; 381 } 382 383 384 void CodeHeap::add_to_freelist(HeapBlock* a) { 385 FreeBlock* b = (FreeBlock*)a; 386 _freelist_length++; 387 388 assert(b != _freelist, "cannot be removed twice"); 389 390 391 // Mark as free and update free space count 392 _freelist_segments += b->length(); 393 b->set_free(); 394 395 // First element in list? 396 if (_freelist == NULL) { 397 _freelist = b; 398 b->set_link(NULL); 399 return; 400 } 401 402 // Since the freelist is ordered (smaller addresses -> larger addresses) and the 403 // element we want to insert into the freelist has a smaller address than the first 404 // element, we can simply add 'b' as the first element and we are done. 405 if (b < _freelist) { 406 // Insert first in list 407 b->set_link(_freelist); 408 _freelist = b; 409 merge_right(_freelist); 410 return; 411 } 412 413 // Scan for right place to put into list. List 414 // is sorted by increasing addresses 415 FreeBlock* prev = _freelist; 416 FreeBlock* cur = _freelist->link(); 417 while(cur != NULL && cur < b) { 418 assert(prev < cur, "Freelist must be ordered"); 419 prev = cur; 420 cur = cur->link(); 421 } 422 assert((prev < b) && (cur == NULL || b < cur), "free-list must be ordered"); 423 insert_after(prev, b); 424 } 425 426 /** 427 * Search freelist for an entry on the list with the best fit. 428 * @return NULL, if no one was found 429 */ 430 FreeBlock* CodeHeap::search_freelist(size_t length, bool is_critical) { 431 FreeBlock* found_block = NULL; 432 FreeBlock* found_prev = NULL; 433 size_t found_length = 0; 434 435 FreeBlock* prev = NULL; 436 FreeBlock* cur = _freelist; 437 const size_t critical_boundary = (size_t)high_boundary() - CodeCacheMinimumFreeSpace; 438 439 // Search for first block that fits 440 while(cur != NULL) { 441 if (cur->length() >= length) { 442 // Non critical allocations are not allowed to use the last part of the code heap. 443 // Make sure the end of the allocation doesn't cross into the last part of the code heap. 444 if (!is_critical && (((size_t)cur + length) > critical_boundary)) { 445 // The freelist is sorted by address - if one fails, all consecutive will also fail. 446 break; 447 } 448 // Remember block, its previous element, and its length 449 found_block = cur; 450 found_prev = prev; 451 found_length = found_block->length(); 452 453 break; 454 } 455 // Next element in list 456 prev = cur; 457 cur = cur->link(); 458 } 459 460 if (found_block == NULL) { 461 // None found 462 return NULL; 463 } 464 465 // Exact (or at least good enough) fit. Remove from list. 466 // Don't leave anything on the freelist smaller than CodeCacheMinBlockLength. 467 if (found_length - length < CodeCacheMinBlockLength) { 468 _freelist_length--; 469 length = found_length; 470 if (found_prev == NULL) { 471 assert(_freelist == found_block, "sanity check"); 472 _freelist = _freelist->link(); 473 } else { 474 assert((found_prev->link() == found_block), "sanity check"); 475 // Unmap element 476 found_prev->set_link(found_block->link()); 477 } 478 } else { 479 // Truncate block and return a pointer to the following block 480 // Set used bit and length on new block 481 found_block->set_length(found_length - length); 482 found_block = following_block(found_block); 483 484 size_t beg = segment_for(found_block); 485 mark_segmap_as_used(beg, beg + length); 486 found_block->set_length(length); 487 } 488 489 found_block->set_used(); 490 _freelist_segments -= length; 491 return found_block; 492 } 493 494 //---------------------------------------------------------------------------- 495 // Non-product code 496 497 #ifndef PRODUCT 498 499 void CodeHeap::print() { 500 tty->print_cr("The Heap"); 501 } 502 503 void CodeHeap::verify() { 504 if (VerifyCodeCache) { 505 size_t len = 0; 506 int count = 0; 507 for(FreeBlock* b = _freelist; b != NULL; b = b->link()) { 508 len += b->length(); 509 count++; 510 // Check if we have merged all free blocks 511 assert(merge_right(b) == false, "Missed merging opportunity"); 512 } 513 // Verify that freelist contains the right amount of free space 514 assert(len == _freelist_segments, "wrong freelist"); 515 516 for(HeapBlock* h = first_block(); h != NULL; h = next_block(h)) { 517 if (h->free()) count--; 518 } 519 // Verify that the freelist contains the same number of blocks 520 // than free blocks found on the full list. 521 assert(count == 0, "missing free blocks"); 522 523 // Verify that the number of free blocks is not out of hand. 524 static int free_block_threshold = 10000; 525 if (count > free_block_threshold) { 526 warning("CodeHeap: # of free blocks > %d", free_block_threshold); 527 // Double the warning limit 528 free_block_threshold *= 2; 529 } 530 } 531 } 532 533 #endif