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(              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(              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 // Returns the current block if available and used.
 283 // If not, it returns the subsequent block (if available), NULL otherwise.
 284 // Free blocks are merged, therefore there is at most one free block
 285 // between two used ones. As a result, the subsequent block (if available) is
 286 // guaranteed to be used.
 287 void* CodeHeap::next_used(HeapBlock* b) const {
 288   if (b != NULL && b->free()) b = next_block(b);
 289   assert(b == NULL || !b->free(), "must be in use or at end of heap");
 290   return (b == NULL) ? NULL : b->allocated_space();
 291 }
 292 
 293 // Returns the first used HeapBlock
 294 HeapBlock* CodeHeap::first_block() const {
 295   if (_next_segment > 0)
 296     return block_at(0);
 297   return NULL;
 298 }
 299 
 300 HeapBlock* CodeHeap::block_start(void* q) const {
 301   HeapBlock* b = (HeapBlock*)find_start(q);
 302   if (b == NULL) return NULL;
 303   return b - 1;
 304 }
 305 
 306 // Returns the next Heap block an offset into one
 307 HeapBlock* CodeHeap::next_block(HeapBlock *b) const {
 308   if (b == NULL) return NULL;
 309   size_t i = segment_for(b) + b->length();
 310   if (i < _next_segment)
 311     return block_at(i);
 312   return NULL;
 313 }
 314 
 315 
 316 // Returns current capacity
 317 size_t CodeHeap::capacity() const {
 318   return _memory.committed_size();
 319 }
 320 
 321 size_t CodeHeap::max_capacity() const {
 322   return _memory.reserved_size();
 323 }
 324 
 325 int CodeHeap::allocated_segments() const {
 326   return (int)_next_segment;
 327 }
 328 
 329 size_t CodeHeap::allocated_capacity() const {
 330   // size of used heap - size on freelist
 331   return segments_to_size(_next_segment - _freelist_segments);
 332 }
 333 
 334 // Returns size of the unallocated heap block
 335 size_t CodeHeap::heap_unallocated_capacity() const {
 336   // Total number of segments - number currently used
 337   return segments_to_size(_number_of_reserved_segments - _next_segment);
 338 }
 339 
 340 // Free list management
 341 
 342 FreeBlock* CodeHeap::following_block(FreeBlock *b) {
 343   return (FreeBlock*)(((address)b) + _segment_size * b->length());
 344 }
 345 
 346 // Inserts block b after a
 347 void CodeHeap::insert_after(FreeBlock* a, FreeBlock* b) {
 348   assert(a != NULL && b != NULL, "must be real pointers");
 349 
 350   // Link b into the list after a
 351   b->set_link(a->link());
 352   a->set_link(b);
 353 
 354   // See if we can merge blocks
 355   merge_right(b); // Try to make b bigger
 356   merge_right(a); // Try to make a include b
 357 }
 358 
 359 // Try to merge this block with the following block
 360 bool CodeHeap::merge_right(FreeBlock* a) {
 361   assert(a->free(), "must be a free block");
 362   if (following_block(a) == a->link()) {
 363     assert(a->link() != NULL && a->link()->free(), "must be free too");
 364     // Update block a to include the following block
 365     a->set_length(a->length() + a->link()->length());
 366     a->set_link(a->link()->link());
 367     // Update find_start map
 368     size_t beg = segment_for(a);
 369     mark_segmap_as_used(beg, beg + a->length());
 370     _freelist_length--;
 371     return true;
 372   }
 373   return false;
 374 }
 375 
 376 
 377 void CodeHeap::add_to_freelist(HeapBlock* a) {
 378   FreeBlock* b = (FreeBlock*)a;
 379   _freelist_length++;
 380 
 381   assert(b != _freelist, "cannot be removed twice");
 382 
 383 
 384   // Mark as free and update free space count
 385   _freelist_segments += b->length();
 386   b->set_free();
 387 
 388   // First element in list?
 389   if (_freelist == NULL) {
 390     _freelist = b;
 391     b->set_link(NULL);
 392     return;
 393   }
 394 
 395   // Since the freelist is ordered (smaller addresses -> larger addresses) and the
 396   // element we want to insert into the freelist has a smaller address than the first
 397   // element, we can simply add 'b' as the first element and we are done.
 398   if (b < _freelist) {
 399     // Insert first in list
 400     b->set_link(_freelist);
 401     _freelist = b;
 402     merge_right(_freelist);
 403     return;
 404   }
 405 
 406   // Scan for right place to put into list. List
 407   // is sorted by increasing addresses
 408   FreeBlock* prev = _freelist;
 409   FreeBlock* cur  = _freelist->link();
 410   while(cur != NULL && cur < b) {
 411     assert(prev < cur, "Freelist must be ordered");
 412     prev = cur;
 413     cur  = cur->link();
 414   }
 415   assert((prev < b) && (cur == NULL || b < cur), "free-list must be ordered");
 416   insert_after(prev, b);
 417 }
 418 
 419 /**
 420  * Search freelist for an entry on the list with the best fit.
 421  * @return NULL, if no one was found
 422  */
 423 FreeBlock* CodeHeap::search_freelist(size_t length) {
 424   FreeBlock* found_block = NULL;
 425   FreeBlock* found_prev  = NULL;
 426   size_t     found_length = 0;
 427 
 428   FreeBlock* prev = NULL;
 429   FreeBlock* cur = _freelist;
 430 
 431   // Search for first block that fits
 432   while(cur != NULL) {
 433     if (cur->length() >= length) {
 434       // Remember block, its previous element, and its length
 435       found_block = cur;
 436       found_prev  = prev;
 437       found_length = found_block->length();
 438 
 439       break;
 440     }
 441     // Next element in list
 442     prev = cur;
 443     cur  = cur->link();
 444   }
 445 
 446   if (found_block == NULL) {
 447     // None found
 448     return NULL;
 449   }
 450 
 451   // Exact (or at least good enough) fit. Remove from list.
 452   // Don't leave anything on the freelist smaller than CodeCacheMinBlockLength.
 453   if (found_length - length < CodeCacheMinBlockLength) {
 454     _freelist_length--;
 455     length = found_length;
 456     if (found_prev == NULL) {
 457       assert(_freelist == found_block, "sanity check");
 458       _freelist = _freelist->link();
 459     } else {
 460       assert((found_prev->link() == found_block), "sanity check");
 461       // Unmap element
 462       found_prev->set_link(found_block->link());
 463     }
 464   } else {
 465     // Truncate block and return a pointer to the following block
 466     // Set used bit and length on new block
 467     found_block->set_length(found_length - length);
 468     found_block = following_block(found_block);
 469 
 470     size_t beg = segment_for(found_block);
 471     mark_segmap_as_used(beg, beg + length);
 472     found_block->set_length(length);
 473   }
 474 
 475   found_block->set_used();
 476   _freelist_segments -= length;
 477   return found_block;
 478 }
 479 
 480 //----------------------------------------------------------------------------
 481 // Non-product code
 482 
 483 #ifndef PRODUCT
 484 
 485 void CodeHeap::print() {
 486   tty->print_cr("The Heap");
 487 }
 488 
 489 void CodeHeap::verify() {
 490   if (VerifyCodeCache) {
 491     size_t len = 0;
 492     int count = 0;
 493     for(FreeBlock* b = _freelist; b != NULL; b = b->link()) {
 494       len += b->length();
 495       count++;
 496       // Check if we have merged all free blocks
 497       assert(merge_right(b) == false, "Missed merging opportunity");
 498     }
 499     // Verify that freelist contains the right amount of free space
 500     assert(len == _freelist_segments, "wrong freelist");
 501 
 502     for(HeapBlock* h = first_block(); h != NULL; h = next_block(h)) {
 503       if (h->free()) count--;
 504     }
 505     // Verify that the freelist contains the same number of blocks
 506     // than free blocks found on the full list.
 507     assert(count == 0, "missing free blocks");
 508 
 509     // Verify that the number of free blocks is not out of hand.
 510     static int free_block_threshold = 10000;
 511     if (count > free_block_threshold) {
 512       warning("CodeHeap: # of free blocks > %d", free_block_threshold);
 513       // Double the warning limit
 514       free_block_threshold *= 2;
 515     }
 516   }
 517 }
 518 
 519 #endif