1 /*
2 * Copyright (c) 1997, 2015, 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 _blob_count = 0;
51 _nmethod_count = 0;
52 _adapter_count = 0;
53 _full_count = 0;
54 }
55
56
57 void CodeHeap::mark_segmap_as_free(size_t beg, size_t end) {
58 assert( beg < _number_of_committed_segments, "interval begin out of bounds");
59 assert(beg < end && end <= _number_of_committed_segments, "interval end out of bounds");
60 // setup _segmap pointers for faster indexing
61 address p = (address)_segmap.low() + beg;
62 address q = (address)_segmap.low() + end;
63 // initialize interval
64 while (p < q) *p++ = free_sentinel;
65 }
66
67
68 void CodeHeap::mark_segmap_as_used(size_t beg, size_t end) {
69 assert( beg < _number_of_committed_segments, "interval begin out of bounds");
70 assert(beg < end && end <= _number_of_committed_segments, "interval end out of bounds");
71 // setup _segmap pointers for faster indexing
72 address p = (address)_segmap.low() + beg;
73 address q = (address)_segmap.low() + end;
74 // initialize interval
75 int i = 0;
76 while (p < q) {
77 *p++ = i++;
78 if (i == free_sentinel) i = 1;
79 }
80 }
81
82
83 static size_t align_to_page_size(size_t size) {
84 const size_t alignment = (size_t)os::vm_page_size();
85 assert(is_power_of_2(alignment), "no kidding ???");
86 return (size + alignment - 1) & ~(alignment - 1);
87 }
88
89
90 void CodeHeap::on_code_mapping(char* base, size_t size) {
91 #ifdef LINUX
92 extern void linux_wrap_code(char* base, size_t size);
93 linux_wrap_code(base, size);
94 #endif
95 }
96
97
98 bool CodeHeap::reserve(ReservedSpace rs, size_t committed_size, size_t segment_size) {
99 assert(rs.size() >= committed_size, "reserved < committed");
100 assert(segment_size >= sizeof(FreeBlock), "segment size is too small");
101 assert(is_power_of_2(segment_size), "segment_size must be a power of 2");
102
103 _segment_size = segment_size;
104 _log2_segment_size = exact_log2(segment_size);
105
106 // Reserve and initialize space for _memory.
107 size_t page_size = os::vm_page_size();
108 if (os::can_execute_large_page_memory()) {
109 const size_t min_pages = 8;
110 page_size = MIN2(os::page_size_for_region_aligned(committed_size, min_pages),
111 os::page_size_for_region_aligned(rs.size(), min_pages));
112 }
113
114 const size_t granularity = os::vm_allocation_granularity();
115 const size_t c_size = align_up(committed_size, page_size);
116
117 os::trace_page_sizes(_name, committed_size, rs.size(), page_size,
118 rs.base(), rs.size());
119 if (!_memory.initialize(rs, c_size)) {
120 return false;
121 }
122
123 on_code_mapping(_memory.low(), _memory.committed_size());
124 _number_of_committed_segments = size_to_segments(_memory.committed_size());
125 _number_of_reserved_segments = size_to_segments(_memory.reserved_size());
126 assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking");
127 const size_t reserved_segments_alignment = MAX2((size_t)os::vm_page_size(), granularity);
128 const size_t reserved_segments_size = align_up(_number_of_reserved_segments, reserved_segments_alignment);
129 const size_t committed_segments_size = align_to_page_size(_number_of_committed_segments);
130
131 // reserve space for _segmap
132 if (!_segmap.initialize(reserved_segments_size, committed_segments_size)) {
133 return false;
134 }
135
136 MemTracker::record_virtual_memory_type((address)_segmap.low_boundary(), mtCode);
137
138 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "could not commit enough space for segment map");
139 assert(_segmap.reserved_size() >= (size_t) _number_of_reserved_segments , "could not reserve enough space for segment map");
140 assert(_segmap.reserved_size() >= _segmap.committed_size() , "just checking");
141
142 // initialize remaining instance variables
143 clear();
144 return true;
145 }
146
147
148 bool CodeHeap::expand_by(size_t size) {
149 // expand _memory space
150 size_t dm = align_to_page_size(_memory.committed_size() + size) - _memory.committed_size();
151 if (dm > 0) {
152 // Use at least the available uncommitted space if 'size' is larger
153 if (_memory.uncommitted_size() != 0 && dm > _memory.uncommitted_size()) {
154 dm = _memory.uncommitted_size();
155 }
156 char* base = _memory.low() + _memory.committed_size();
157 if (!_memory.expand_by(dm)) return false;
158 on_code_mapping(base, dm);
159 size_t i = _number_of_committed_segments;
160 _number_of_committed_segments = size_to_segments(_memory.committed_size());
161 assert(_number_of_reserved_segments == size_to_segments(_memory.reserved_size()), "number of reserved segments should not change");
162 assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking");
163 // expand _segmap space
164 size_t ds = align_to_page_size(_number_of_committed_segments) - _segmap.committed_size();
165 if ((ds > 0) && !_segmap.expand_by(ds)) {
166 return false;
167 }
168 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "just checking");
169 // initialize additional segmap entries
170 mark_segmap_as_free(i, _number_of_committed_segments);
171 }
172 return true;
173 }
174
175 void CodeHeap::clear() {
176 _next_segment = 0;
177 mark_segmap_as_free(0, _number_of_committed_segments);
178 }
179
180
181 void* CodeHeap::allocate(size_t instance_size) {
182 size_t number_of_segments = size_to_segments(instance_size + header_size());
183 assert(segments_to_size(number_of_segments) >= sizeof(FreeBlock), "not enough room for FreeList");
184
185 // First check if we can satisfy request from freelist
186 NOT_PRODUCT(verify());
187 HeapBlock* block = search_freelist(number_of_segments);
188 NOT_PRODUCT(verify());
189
190 if (block != NULL) {
191 assert(block->length() >= number_of_segments && block->length() < number_of_segments + CodeCacheMinBlockLength, "sanity check");
192 assert(!block->free(), "must be marked free");
193 guarantee((char*) block >= _memory.low_boundary() && (char*) block < _memory.high(),
194 "The newly allocated block " INTPTR_FORMAT " is not within the heap "
195 "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT,
196 p2i(block), p2i(_memory.low_boundary()), p2i(_memory.high()));
197 DEBUG_ONLY(memset((void*)block->allocated_space(), badCodeHeapNewVal, instance_size));
198 _max_allocated_capacity = MAX2(_max_allocated_capacity, allocated_capacity());
199 _blob_count++;
200 return block->allocated_space();
201 }
202
203 // Ensure minimum size for allocation to the heap.
204 number_of_segments = MAX2((int)CodeCacheMinBlockLength, (int)number_of_segments);
205
206 if (_next_segment + number_of_segments <= _number_of_committed_segments) {
207 mark_segmap_as_used(_next_segment, _next_segment + number_of_segments);
208 HeapBlock* b = block_at(_next_segment);
209 b->initialize(number_of_segments);
210 _next_segment += number_of_segments;
211 guarantee((char*) b >= _memory.low_boundary() && (char*) block < _memory.high(),
212 "The newly allocated block " INTPTR_FORMAT " is not within the heap "
213 "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT,
214 p2i(b), p2i(_memory.low_boundary()), p2i(_memory.high()));
215 DEBUG_ONLY(memset((void *)b->allocated_space(), badCodeHeapNewVal, instance_size));
216 _max_allocated_capacity = MAX2(_max_allocated_capacity, allocated_capacity());
217 _blob_count++;
218 return b->allocated_space();
219 } else {
220 return NULL;
221 }
222 }
223
224
225 void CodeHeap::deallocate(void* p) {
226 assert(p == find_start(p), "illegal deallocation");
227 // Find start of HeapBlock
228 HeapBlock* b = (((HeapBlock *)p) - 1);
229 assert(b->allocated_space() == p, "sanity check");
230 guarantee((char*) b >= _memory.low_boundary() && (char*) b < _memory.high(),
231 "The block to be deallocated " INTPTR_FORMAT " is not within the heap "
232 "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT,
233 p2i(b), p2i(_memory.low_boundary()), p2i(_memory.high()));
234 DEBUG_ONLY(memset((void *)b->allocated_space(), badCodeHeapFreeVal,
235 segments_to_size(b->length()) - sizeof(HeapBlock)));
236 add_to_freelist(b);
237 NOT_PRODUCT(verify());
238 }
239
240 /**
241 * Uses segment map to find the the start (header) of a nmethod. This works as follows:
242 * The memory of the code cache is divided into 'segments'. The size of a segment is
243 * determined by -XX:CodeCacheSegmentSize=XX. Allocation in the code cache can only
244 * happen at segment boundaries. A pointer in the code cache can be mapped to a segment
245 * by calling segment_for(addr). Each time memory is requested from the code cache,
246 * the segmap is updated accordingly. See the following example, which illustrates the
247 * state of code cache and the segment map: (seg -> segment, nm ->nmethod)
248 *
249 * code cache segmap
250 * ----------- ---------
251 * seg 1 | nm 1 | -> | 0 |
252 * seg 2 | nm 1 | -> | 1 |
253 * ... | nm 1 | -> | .. |
254 * seg m | nm 2 | -> | 0 |
255 * seg m+1 | nm 2 | -> | 1 |
256 * ... | nm 2 | -> | 2 |
257 * ... | nm 2 | -> | .. |
258 * ... | nm 2 | -> | 0xFE |
259 * seg m+n | nm 2 | -> | 1 |
260 * ... | nm 2 | -> | |
261 *
262 * A value of '0' in the segmap indicates that this segment contains the beginning of
263 * an nmethod. Let's walk through a simple example: If we want to find the start of
264 * an nmethod that falls into seg 2, we read the value of the segmap[2]. The value
265 * is an offset that points to the segment that contains the start of the nmethod.
266 * Another example: If we want to get the start of nm 2, and we happen to get a pointer
267 * that points to seg m+n, we first read seg[n+m], which returns '1'. So we have to
268 * do one more read of the segmap[m+n-1] to finally get the segment header.
269 */
270 void* CodeHeap::find_start(void* p) const {
271 if (!contains(p)) {
272 return NULL;
273 }
274 size_t seg_idx = segment_for(p);
275 address seg_map = (address)_segmap.low();
276 if (is_segment_unused(seg_map[seg_idx])) {
277 return NULL;
278 }
279 while (seg_map[seg_idx] > 0) {
280 seg_idx -= (int)seg_map[seg_idx];
281 }
282
283 HeapBlock* h = block_at(seg_idx);
284 if (h->free()) {
285 return NULL;
286 }
287 return h->allocated_space();
288 }
289
290 CodeBlob* CodeHeap::find_blob_unsafe(void* start) const {
291 CodeBlob* result = (CodeBlob*)CodeHeap::find_start(start);
292 if (result != NULL && result->blob_contains((address)start)) {
293 return result;
294 }
295 return NULL;
296 }
297
298 size_t CodeHeap::alignment_unit() const {
299 // this will be a power of two
300 return _segment_size;
301 }
302
303
304 size_t CodeHeap::alignment_offset() const {
305 // The lowest address in any allocated block will be
306 // equal to alignment_offset (mod alignment_unit).
307 return sizeof(HeapBlock) & (_segment_size - 1);
308 }
309
310 // Returns the current block if available and used.
311 // If not, it returns the subsequent block (if available), NULL otherwise.
312 // Free blocks are merged, therefore there is at most one free block
313 // between two used ones. As a result, the subsequent block (if available) is
314 // guaranteed to be used.
315 void* CodeHeap::next_used(HeapBlock* b) const {
316 if (b != NULL && b->free()) b = next_block(b);
317 assert(b == NULL || !b->free(), "must be in use or at end of heap");
318 return (b == NULL) ? NULL : b->allocated_space();
319 }
320
321 // Returns the first used HeapBlock
322 HeapBlock* CodeHeap::first_block() const {
323 if (_next_segment > 0)
324 return block_at(0);
325 return NULL;
326 }
327
328 HeapBlock* CodeHeap::block_start(void* q) const {
329 HeapBlock* b = (HeapBlock*)find_start(q);
330 if (b == NULL) return NULL;
331 return b - 1;
332 }
333
334 // Returns the next Heap block an offset into one
335 HeapBlock* CodeHeap::next_block(HeapBlock *b) const {
336 if (b == NULL) return NULL;
337 size_t i = segment_for(b) + b->length();
338 if (i < _next_segment)
339 return block_at(i);
340 return NULL;
341 }
342
343
344 // Returns current capacity
345 size_t CodeHeap::capacity() const {
346 return _memory.committed_size();
347 }
348
349 size_t CodeHeap::max_capacity() const {
350 return _memory.reserved_size();
351 }
352
353 int CodeHeap::allocated_segments() const {
354 return (int)_next_segment;
355 }
356
357 size_t CodeHeap::allocated_capacity() const {
358 // size of used heap - size on freelist
359 return segments_to_size(_next_segment - _freelist_segments);
360 }
361
362 // Returns size of the unallocated heap block
363 size_t CodeHeap::heap_unallocated_capacity() const {
364 // Total number of segments - number currently used
365 return segments_to_size(_number_of_reserved_segments - _next_segment);
366 }
367
368 // Free list management
369
370 FreeBlock* CodeHeap::following_block(FreeBlock *b) {
371 return (FreeBlock*)(((address)b) + _segment_size * b->length());
372 }
373
374 // Inserts block b after a
375 void CodeHeap::insert_after(FreeBlock* a, FreeBlock* b) {
376 assert(a != NULL && b != NULL, "must be real pointers");
377
378 // Link b into the list after a
379 b->set_link(a->link());
380 a->set_link(b);
381
382 // See if we can merge blocks
383 merge_right(b); // Try to make b bigger
384 merge_right(a); // Try to make a include b
385 }
386
387 // Try to merge this block with the following block
388 bool CodeHeap::merge_right(FreeBlock* a) {
389 assert(a->free(), "must be a free block");
390 if (following_block(a) == a->link()) {
391 assert(a->link() != NULL && a->link()->free(), "must be free too");
392 // Update block a to include the following block
393 a->set_length(a->length() + a->link()->length());
394 a->set_link(a->link()->link());
395 // Update find_start map
396 size_t beg = segment_for(a);
397 mark_segmap_as_used(beg, beg + a->length());
398 _freelist_length--;
399 return true;
400 }
401 return false;
402 }
403
404
405 void CodeHeap::add_to_freelist(HeapBlock* a) {
406 FreeBlock* b = (FreeBlock*)a;
407 _freelist_length++;
408
409 assert(b != _freelist, "cannot be removed twice");
410
411
412 // Mark as free and update free space count
413 _freelist_segments += b->length();
414 b->set_free();
415
416 // First element in list?
417 if (_freelist == NULL) {
418 _freelist = b;
419 b->set_link(NULL);
420 return;
421 }
422
423 // Since the freelist is ordered (smaller addresses -> larger addresses) and the
424 // element we want to insert into the freelist has a smaller address than the first
425 // element, we can simply add 'b' as the first element and we are done.
426 if (b < _freelist) {
427 // Insert first in list
428 b->set_link(_freelist);
429 _freelist = b;
430 merge_right(_freelist);
431 return;
432 }
433
434 // Scan for right place to put into list. List
435 // is sorted by increasing addresses
436 FreeBlock* prev = _freelist;
437 FreeBlock* cur = _freelist->link();
438 while(cur != NULL && cur < b) {
439 assert(prev < cur, "Freelist must be ordered");
440 prev = cur;
441 cur = cur->link();
442 }
443 assert((prev < b) && (cur == NULL || b < cur), "free-list must be ordered");
444 insert_after(prev, b);
445 }
446
447 /**
448 * Search freelist for an entry on the list with the best fit.
449 * @return NULL, if no one was found
450 */
451 FreeBlock* CodeHeap::search_freelist(size_t length) {
452 FreeBlock* found_block = NULL;
453 FreeBlock* found_prev = NULL;
454 size_t found_length = 0;
455
456 FreeBlock* prev = NULL;
457 FreeBlock* cur = _freelist;
458
459 // Search for first block that fits
460 while(cur != NULL) {
461 if (cur->length() >= length) {
462 // Remember block, its previous element, and its length
463 found_block = cur;
464 found_prev = prev;
465 found_length = found_block->length();
466
467 break;
468 }
469 // Next element in list
470 prev = cur;
471 cur = cur->link();
472 }
473
474 if (found_block == NULL) {
475 // None found
476 return NULL;
477 }
478
479 // Exact (or at least good enough) fit. Remove from list.
480 // Don't leave anything on the freelist smaller than CodeCacheMinBlockLength.
481 if (found_length - length < CodeCacheMinBlockLength) {
482 _freelist_length--;
483 length = found_length;
484 if (found_prev == NULL) {
485 assert(_freelist == found_block, "sanity check");
486 _freelist = _freelist->link();
487 } else {
488 assert((found_prev->link() == found_block), "sanity check");
489 // Unmap element
490 found_prev->set_link(found_block->link());
491 }
492 } else {
493 // Truncate block and return a pointer to the following block
494 // Set used bit and length on new block
495 found_block->set_length(found_length - length);
496 found_block = following_block(found_block);
497
498 size_t beg = segment_for(found_block);
499 mark_segmap_as_used(beg, beg + length);
500 found_block->set_length(length);
501 }
502
503 found_block->set_used();
504 _freelist_segments -= length;
505 return found_block;
506 }
507
508 //----------------------------------------------------------------------------
509 // Non-product code
510
511 #ifndef PRODUCT
512
513 void CodeHeap::print() {
514 tty->print_cr("The Heap");
515 }
516
517 void CodeHeap::verify() {
518 if (VerifyCodeCache) {
519 size_t len = 0;
520 int count = 0;
521 for(FreeBlock* b = _freelist; b != NULL; b = b->link()) {
522 len += b->length();
523 count++;
524 // Check if we have merged all free blocks
525 assert(merge_right(b) == false, "Missed merging opportunity");
526 }
527 // Verify that freelist contains the right amount of free space
528 assert(len == _freelist_segments, "wrong freelist");
529
530 for(HeapBlock* h = first_block(); h != NULL; h = next_block(h)) {
531 if (h->free()) count--;
532 }
533 // Verify that the freelist contains the same number of blocks
534 // than free blocks found on the full list.
535 assert(count == 0, "missing free blocks");
536
537 // Verify that the number of free blocks is not out of hand.
538 static int free_block_threshold = 10000;
539 if (count > free_block_threshold) {
540 warning("CodeHeap: # of free blocks > %d", free_block_threshold);
541 // Double the warning limit
542 free_block_threshold *= 2;
543 }
544 }
545 }
546
547 #endif