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_aligned(committed_size, min_pages), 108 os::page_size_for_region_aligned(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) { 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); 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 (_next_segment + number_of_segments <= _number_of_committed_segments) { 195 mark_segmap_as_used(_next_segment, _next_segment + number_of_segments); 196 HeapBlock* b = block_at(_next_segment); 197 b->initialize(number_of_segments); 198 _next_segment += number_of_segments; 199 DEBUG_ONLY(memset((void *)b->allocated_space(), badCodeHeapNewVal, instance_size)); 200 _max_allocated_capacity = MAX2(_max_allocated_capacity, allocated_capacity()); 201 return b->allocated_space(); 202 } else { 203 return NULL; 204 } 205 } 206 207 208 void CodeHeap::deallocate(void* p) { 209 assert(p == find_start(p), "illegal deallocation"); 210 // Find start of HeapBlock 211 HeapBlock* b = (((HeapBlock *)p) - 1); 212 assert(b->allocated_space() == p, "sanity check"); 213 DEBUG_ONLY(memset((void *)b->allocated_space(), badCodeHeapFreeVal, 214 segments_to_size(b->length()) - sizeof(HeapBlock))); 215 add_to_freelist(b); 216 NOT_PRODUCT(verify()); 217 } 218 219 /** 220 * Uses segment map to find the the start (header) of a nmethod. This works as follows: 221 * The memory of the code cache is divided into 'segments'. The size of a segment is 222 * determined by -XX:CodeCacheSegmentSize=XX. Allocation in the code cache can only 223 * happen at segment boundaries. A pointer in the code cache can be mapped to a segment 224 * by calling segment_for(addr). Each time memory is requested from the code cache, 225 * the segmap is updated accordingly. See the following example, which illustrates the 226 * state of code cache and the segment map: (seg -> segment, nm ->nmethod) 227 * 228 * code cache segmap 229 * ----------- --------- 230 * seg 1 | nm 1 | -> | 0 | 231 * seg 2 | nm 1 | -> | 1 | 232 * ... | nm 1 | -> | .. | 233 * seg m | nm 2 | -> | 0 | 234 * seg m+1 | nm 2 | -> | 1 | 235 * ... | nm 2 | -> | 2 | 236 * ... | nm 2 | -> | .. | 237 * ... | nm 2 | -> | 0xFE | 238 * seg m+n | nm 2 | -> | 1 | 239 * ... | nm 2 | -> | | 240 * 241 * A value of '0' in the segmap indicates that this segment contains the beginning of 242 * an nmethod. Let's walk through a simple example: If we want to find the start of 243 * an nmethod that falls into seg 2, we read the value of the segmap[2]. The value 244 * is an offset that points to the segment that contains the start of the nmethod. 245 * Another example: If we want to get the start of nm 2, and we happen to get a pointer 246 * that points to seg m+n, we first read seg[n+m], which returns '1'. So we have to 247 * do one more read of the segmap[m+n-1] to finally get the segment header. 248 */ 249 void* CodeHeap::find_start(void* p) const { 250 if (!contains(p)) { 251 return NULL; 252 } 253 size_t seg_idx = segment_for(p); 254 address seg_map = (address)_segmap.low(); 255 if (is_segment_unused(seg_map[seg_idx])) { 256 return NULL; 257 } 258 while (seg_map[seg_idx] > 0) { 259 seg_idx -= (int)seg_map[seg_idx]; 260 } 261 262 HeapBlock* h = block_at(seg_idx); 263 if (h->free()) { 264 return NULL; 265 } 266 return h->allocated_space(); 267 } 268 269 270 size_t CodeHeap::alignment_unit() const { 271 // this will be a power of two 272 return _segment_size; 273 } 274 275 276 size_t CodeHeap::alignment_offset() const { 277 // The lowest address in any allocated block will be 278 // equal to alignment_offset (mod alignment_unit). 279 return sizeof(HeapBlock) & (_segment_size - 1); 280 } 281 282 // Finds the next free heapblock. If the current one is free, that it returned 283 void* CodeHeap::next_free(HeapBlock* b) const { 284 // Since free blocks are merged, there is max. on free block 285 // between two used ones 286 if (b != NULL && b->free()) b = next_block(b); 287 assert(b == NULL || !b->free(), "must be in use or at end of heap"); 288 return (b == NULL) ? NULL : b->allocated_space(); 289 } 290 291 // Returns the first used HeapBlock 292 HeapBlock* CodeHeap::first_block() const { 293 if (_next_segment > 0) 294 return block_at(0); 295 return NULL; 296 } 297 298 HeapBlock* CodeHeap::block_start(void* q) const { 299 HeapBlock* b = (HeapBlock*)find_start(q); 300 if (b == NULL) return NULL; 301 return b - 1; 302 } 303 304 // Returns the next Heap block an offset into one 305 HeapBlock* CodeHeap::next_block(HeapBlock *b) const { 306 if (b == NULL) return NULL; 307 size_t i = segment_for(b) + b->length(); 308 if (i < _next_segment) 309 return block_at(i); 310 return NULL; 311 } 312 313 314 // Returns current capacity 315 size_t CodeHeap::capacity() const { 316 return _memory.committed_size(); 317 } 318 319 size_t CodeHeap::max_capacity() const { 320 return _memory.reserved_size(); 321 } 322 323 int CodeHeap::allocated_segments() const { 324 return (int)_next_segment; 325 } 326 327 size_t CodeHeap::allocated_capacity() const { 328 // size of used heap - size on freelist 329 return segments_to_size(_next_segment - _freelist_segments); 330 } 331 332 // Returns size of the unallocated heap block 333 size_t CodeHeap::heap_unallocated_capacity() const { 334 // Total number of segments - number currently used 335 return segments_to_size(_number_of_reserved_segments - _next_segment); 336 } 337 338 // Free list management 339 340 FreeBlock* CodeHeap::following_block(FreeBlock *b) { 341 return (FreeBlock*)(((address)b) + _segment_size * b->length()); 342 } 343 344 // Inserts block b after a 345 void CodeHeap::insert_after(FreeBlock* a, FreeBlock* b) { 346 assert(a != NULL && b != NULL, "must be real pointers"); 347 348 // Link b into the list after a 349 b->set_link(a->link()); 350 a->set_link(b); 351 352 // See if we can merge blocks 353 merge_right(b); // Try to make b bigger 354 merge_right(a); // Try to make a include b 355 } 356 357 // Try to merge this block with the following block 358 bool CodeHeap::merge_right(FreeBlock* a) { 359 assert(a->free(), "must be a free block"); 360 if (following_block(a) == a->link()) { 361 assert(a->link() != NULL && a->link()->free(), "must be free too"); 362 // Update block a to include the following block 363 a->set_length(a->length() + a->link()->length()); 364 a->set_link(a->link()->link()); 365 // Update find_start map 366 size_t beg = segment_for(a); 367 mark_segmap_as_used(beg, beg + a->length()); 368 _freelist_length--; 369 return true; 370 } 371 return false; 372 } 373 374 375 void CodeHeap::add_to_freelist(HeapBlock* a) { 376 FreeBlock* b = (FreeBlock*)a; 377 _freelist_length++; 378 379 assert(b != _freelist, "cannot be removed twice"); 380 381 382 // Mark as free and update free space count 383 _freelist_segments += b->length(); 384 b->set_free(); 385 386 // First element in list? 387 if (_freelist == NULL) { 388 _freelist = b; 389 b->set_link(NULL); 390 return; 391 } 392 393 // Since the freelist is ordered (smaller addresses -> larger addresses) and the 394 // element we want to insert into the freelist has a smaller address than the first 395 // element, we can simply add 'b' as the first element and we are done. 396 if (b < _freelist) { 397 // Insert first in list 398 b->set_link(_freelist); 399 _freelist = b; 400 merge_right(_freelist); 401 return; 402 } 403 404 // Scan for right place to put into list. List 405 // is sorted by increasing addresses 406 FreeBlock* prev = _freelist; 407 FreeBlock* cur = _freelist->link(); 408 while(cur != NULL && cur < b) { 409 assert(prev < cur, "Freelist must be ordered"); 410 prev = cur; 411 cur = cur->link(); 412 } 413 assert((prev < b) && (cur == NULL || b < cur), "free-list must be ordered"); 414 insert_after(prev, b); 415 } 416 417 /** 418 * Search freelist for an entry on the list with the best fit. 419 * @return NULL, if no one was found 420 */ 421 FreeBlock* CodeHeap::search_freelist(size_t length) { 422 FreeBlock* found_block = NULL; 423 FreeBlock* found_prev = NULL; 424 size_t found_length = 0; 425 426 FreeBlock* prev = NULL; 427 FreeBlock* cur = _freelist; 428 429 // Search for first block that fits 430 while(cur != NULL) { 431 if (cur->length() >= length) { 432 // Remember block, its previous element, and its length 433 found_block = cur; 434 found_prev = prev; 435 found_length = found_block->length(); 436 437 break; 438 } 439 // Next element in list 440 prev = cur; 441 cur = cur->link(); 442 } 443 444 if (found_block == NULL) { 445 // None found 446 return NULL; 447 } 448 449 // Exact (or at least good enough) fit. Remove from list. 450 // Don't leave anything on the freelist smaller than CodeCacheMinBlockLength. 451 if (found_length - length < CodeCacheMinBlockLength) { 452 _freelist_length--; 453 length = found_length; 454 if (found_prev == NULL) { 455 assert(_freelist == found_block, "sanity check"); 456 _freelist = _freelist->link(); 457 } else { 458 assert((found_prev->link() == found_block), "sanity check"); 459 // Unmap element 460 found_prev->set_link(found_block->link()); 461 } 462 } else { 463 // Truncate block and return a pointer to the following block 464 // Set used bit and length on new block 465 found_block->set_length(found_length - length); 466 found_block = following_block(found_block); 467 468 size_t beg = segment_for(found_block); 469 mark_segmap_as_used(beg, beg + length); 470 found_block->set_length(length); 471 } 472 473 found_block->set_used(); 474 _freelist_segments -= length; 475 return found_block; 476 } 477 478 //---------------------------------------------------------------------------- 479 // Non-product code 480 481 #ifndef PRODUCT 482 483 void CodeHeap::print() { 484 tty->print_cr("The Heap"); 485 } 486 487 void CodeHeap::verify() { 488 if (VerifyCodeCache) { 489 size_t len = 0; 490 int count = 0; 491 for(FreeBlock* b = _freelist; b != NULL; b = b->link()) { 492 len += b->length(); 493 count++; 494 // Check if we have merged all free blocks 495 assert(merge_right(b) == false, "Missed merging opportunity"); 496 } 497 // Verify that freelist contains the right amount of free space 498 assert(len == _freelist_segments, "wrong freelist"); 499 500 for(HeapBlock* h = first_block(); h != NULL; h = next_block(h)) { 501 if (h->free()) count--; 502 } 503 // Verify that the freelist contains the same number of blocks 504 // than free blocks found on the full list. 505 assert(count == 0, "missing free blocks"); 506 507 // Verify that the number of free blocks is not out of hand. 508 static int free_block_threshold = 10000; 509 if (count > free_block_threshold) { 510 warning("CodeHeap: # of free blocks > %d", free_block_threshold); 511 // Double the warning limit 512 free_block_threshold *= 2; 513 } 514 } 515 } 516 517 #endif