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