1 /*
2 * Copyright (c) 1997, 2019, 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 #include "utilities/align.hpp"
31
32 size_t CodeHeap::header_size() {
33 return sizeof(HeapBlock);
34 }
35
36
37 // Implementation of Heap
38
39 CodeHeap::CodeHeap(const char* name, const int code_blob_type)
40 : _code_blob_type(code_blob_type) {
41 _name = name;
42 _number_of_committed_segments = 0;
43 _number_of_reserved_segments = 0;
44 _segment_size = 0;
45 _log2_segment_size = 0;
46 _next_segment = 0;
47 _freelist = NULL;
48 _freelist_segments = 0;
49 _freelist_length = 0;
50 _max_allocated_capacity = 0;
51 _blob_count = 0;
52 _nmethod_count = 0;
53 _adapter_count = 0;
54 _full_count = 0;
55 }
56
57
58 // The segmap is marked free for that part of the heap
59 // which has not been allocated yet (beyond _next_segment).
60 // "Allocated" space in this context means there exists a
61 // HeapBlock or a FreeBlock describing this space.
62 void CodeHeap::mark_segmap_as_free(size_t beg, size_t end) {
63 assert( beg < _number_of_committed_segments, "interval begin out of bounds");
64 assert(beg < end && end <= _number_of_committed_segments, "interval end out of bounds");
65 // setup _segmap pointers for faster indexing
66 address p = (address)_segmap.low() + beg;
67 address q = (address)_segmap.low() + end;
68 // initialize interval
69 memset(p, free_sentinel, q-p);
70 }
71
72 // Don't get confused here.
73 // All existing blocks, no matter if they are used() or free(),
74 // have their segmap marked as used. This allows to find the
75 // block header (HeapBlock or FreeBlock) for any pointer
76 // within the allocated range (upper limit: _next_segment).
77 void CodeHeap::mark_segmap_as_used(size_t beg, size_t end) {
78 assert( beg < _number_of_committed_segments, "interval begin out of bounds");
79 assert(beg < end && end <= _number_of_committed_segments, "interval end out of bounds");
80 // setup _segmap pointers for faster indexing
81 address p = (address)_segmap.low() + beg;
82 address q = (address)_segmap.low() + end;
83 // initialize interval
84 int i = 0;
85 while (p < q) {
86 *p++ = i++;
87 if (i == free_sentinel) i = 1;
88 }
89 }
90
91
92 static size_t align_to_page_size(size_t size) {
93 const size_t alignment = (size_t)os::vm_page_size();
94 assert(is_power_of_2(alignment), "no kidding ???");
95 return (size + alignment - 1) & ~(alignment - 1);
96 }
97
98
99 void CodeHeap::on_code_mapping(char* base, size_t size) {
100 #ifdef LINUX
101 extern void linux_wrap_code(char* base, size_t size);
102 linux_wrap_code(base, size);
103 #endif
104 }
105
106
107 bool CodeHeap::reserve(ReservedSpace rs, size_t committed_size, size_t segment_size) {
108 assert(rs.size() >= committed_size, "reserved < committed");
109 assert(segment_size >= sizeof(FreeBlock), "segment size is too small");
110 assert(is_power_of_2(segment_size), "segment_size must be a power of 2");
111
112 _segment_size = segment_size;
113 _log2_segment_size = exact_log2(segment_size);
114
115 // Reserve and initialize space for _memory.
116 size_t page_size = os::vm_page_size();
117 if (os::can_execute_large_page_memory()) {
118 const size_t min_pages = 8;
119 page_size = MIN2(os::page_size_for_region_aligned(committed_size, min_pages),
120 os::page_size_for_region_aligned(rs.size(), min_pages));
121 }
122
123 const size_t granularity = os::vm_allocation_granularity();
124 const size_t c_size = align_up(committed_size, page_size);
125
126 os::trace_page_sizes(_name, committed_size, rs.size(), page_size,
127 rs.base(), rs.size());
128 if (!_memory.initialize(rs, c_size)) {
129 return false;
130 }
131
132 on_code_mapping(_memory.low(), _memory.committed_size());
133 _number_of_committed_segments = size_to_segments(_memory.committed_size());
134 _number_of_reserved_segments = size_to_segments(_memory.reserved_size());
135 assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking");
136 const size_t reserved_segments_alignment = MAX2((size_t)os::vm_page_size(), granularity);
137 const size_t reserved_segments_size = align_up(_number_of_reserved_segments, reserved_segments_alignment);
138 const size_t committed_segments_size = align_to_page_size(_number_of_committed_segments);
139
140 // reserve space for _segmap
141 if (!_segmap.initialize(reserved_segments_size, committed_segments_size)) {
142 return false;
143 }
144
145 MemTracker::record_virtual_memory_type((address)_segmap.low_boundary(), mtCode);
146
147 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "could not commit enough space for segment map");
148 assert(_segmap.reserved_size() >= (size_t) _number_of_reserved_segments , "could not reserve enough space for segment map");
149 assert(_segmap.reserved_size() >= _segmap.committed_size() , "just checking");
150
151 // initialize remaining instance variables
152 clear();
153 return true;
154 }
155
156
157 bool CodeHeap::expand_by(size_t size) {
158 // expand _memory space
159 size_t dm = align_to_page_size(_memory.committed_size() + size) - _memory.committed_size();
160 if (dm > 0) {
161 // Use at least the available uncommitted space if 'size' is larger
162 if (_memory.uncommitted_size() != 0 && dm > _memory.uncommitted_size()) {
163 dm = _memory.uncommitted_size();
164 }
165 char* base = _memory.low() + _memory.committed_size();
166 if (!_memory.expand_by(dm)) return false;
167 on_code_mapping(base, dm);
168 size_t i = _number_of_committed_segments;
169 _number_of_committed_segments = size_to_segments(_memory.committed_size());
170 assert(_number_of_reserved_segments == size_to_segments(_memory.reserved_size()), "number of reserved segments should not change");
171 assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking");
172 // expand _segmap space
173 size_t ds = align_to_page_size(_number_of_committed_segments) - _segmap.committed_size();
174 if ((ds > 0) && !_segmap.expand_by(ds)) {
175 return false;
176 }
177 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "just checking");
178 // initialize additional segmap entries
179 mark_segmap_as_free(i, _number_of_committed_segments);
180 }
181 return true;
182 }
183
184 void CodeHeap::clear() {
185 _next_segment = 0;
186 mark_segmap_as_free(0, _number_of_committed_segments);
187 }
188
189
190 void* CodeHeap::allocate(size_t instance_size) {
191 size_t number_of_segments = size_to_segments(instance_size + header_size());
192 assert(segments_to_size(number_of_segments) >= sizeof(FreeBlock), "not enough room for FreeList");
193
194 // First check if we can satisfy request from freelist
195 NOT_PRODUCT(verify());
196 HeapBlock* block = search_freelist(number_of_segments);
197 NOT_PRODUCT(verify());
198
199 if (block != NULL) {
200 assert(!block->free(), "must be marked free");
201 guarantee((char*) block >= _memory.low_boundary() && (char*) block < _memory.high(),
202 "The newly allocated block " INTPTR_FORMAT " is not within the heap "
203 "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT,
204 p2i(block), p2i(_memory.low_boundary()), p2i(_memory.high()));
205 DEBUG_ONLY(memset((void*)block->allocated_space(), badCodeHeapNewVal, instance_size));
206 _max_allocated_capacity = MAX2(_max_allocated_capacity, allocated_capacity());
207 _blob_count++;
208 return block->allocated_space();
209 }
210
211 // Ensure minimum size for allocation to the heap.
212 number_of_segments = MAX2((int)CodeCacheMinBlockLength, (int)number_of_segments);
213
214 if (_next_segment + number_of_segments <= _number_of_committed_segments) {
215 mark_segmap_as_used(_next_segment, _next_segment + number_of_segments);
216 HeapBlock* b = block_at(_next_segment);
217 b->initialize(number_of_segments);
218 _next_segment += number_of_segments;
219 guarantee((char*) b >= _memory.low_boundary() && (char*) block < _memory.high(),
220 "The newly allocated block " INTPTR_FORMAT " is not within the heap "
221 "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT,
222 p2i(b), p2i(_memory.low_boundary()), p2i(_memory.high()));
223 DEBUG_ONLY(memset((void *)b->allocated_space(), badCodeHeapNewVal, instance_size));
224 _max_allocated_capacity = MAX2(_max_allocated_capacity, allocated_capacity());
225 _blob_count++;
226 return b->allocated_space();
227 } else {
228 return NULL;
229 }
230 }
231
232 // Split the given block into two at the given segment.
233 // This is helpful when a block was allocated too large
234 // to trim off the unused space at the end (interpreter).
235 // It also helps with splitting a large free block during allocation.
236 // Usage state (used or free) must be set by caller since
237 // we don't know if the resulting blocks will be used or free.
238 // split_at is the segment number (relative to segment_for(b))
239 // where the split happens. The segment with relative
240 // number split_at is the first segment of the split-off block.
241 HeapBlock* CodeHeap::split_block(HeapBlock *b, size_t split_at) {
242 if (b == NULL) return NULL;
243 // After the split, both blocks must have a size of at least CodeCacheMinBlockLength
244 assert((split_at >= CodeCacheMinBlockLength) && (split_at + CodeCacheMinBlockLength <= b->length()),
245 "split position(%d) out of range [0..%d]", (int)split_at, (int)b->length());
246 size_t split_segment = segment_for(b) + split_at;
247 size_t b_size = b->length();
248 size_t newb_size = b_size - split_at;
249
250 HeapBlock* newb = block_at(split_segment);
251 newb->set_length(newb_size);
252 mark_segmap_as_used(segment_for(newb), segment_for(newb) + newb_size);
253 b->set_length(split_at);
254 return newb;
255 }
256
257 void CodeHeap::deallocate_tail(void* p, size_t used_size) {
258 assert(p == find_start(p), "illegal deallocation");
259 // Find start of HeapBlock
260 HeapBlock* b = (((HeapBlock *)p) - 1);
261 assert(b->allocated_space() == p, "sanity check");
262
263 size_t actual_number_of_segments = b->length();
264 size_t used_number_of_segments = size_to_segments(used_size + header_size());
265 size_t unused_number_of_segments = actual_number_of_segments - used_number_of_segments;
266 guarantee(used_number_of_segments <= actual_number_of_segments, "Must be!");
267
268 HeapBlock* f = split_block(b, used_number_of_segments);
269 DEBUG_ONLY(memset((void *)f->allocated_space(), badCodeHeapFreeVal,
270 segments_to_size(unused_number_of_segments) - sizeof(HeapBlock)));
271 add_to_freelist(f);
272 NOT_PRODUCT(verify());
273 }
274
275 void CodeHeap::deallocate(void* p) {
276 assert(p == find_start(p), "illegal deallocation");
277 // Find start of HeapBlock
278 HeapBlock* b = (((HeapBlock *)p) - 1);
279 assert(b->allocated_space() == p, "sanity check");
280 guarantee((char*) b >= _memory.low_boundary() && (char*) b < _memory.high(),
281 "The block to be deallocated " INTPTR_FORMAT " is not within the heap "
282 "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT,
283 p2i(b), p2i(_memory.low_boundary()), p2i(_memory.high()));
284 DEBUG_ONLY(memset((void *)b->allocated_space(), badCodeHeapFreeVal,
285 segments_to_size(b->length()) - sizeof(HeapBlock)));
286 add_to_freelist(b);
287 NOT_PRODUCT(verify());
288 }
289
290 /**
291 * Uses segment map to find the the start (header) of a nmethod. This works as follows:
292 * The memory of the code cache is divided into 'segments'. The size of a segment is
293 * determined by -XX:CodeCacheSegmentSize=XX. Allocation in the code cache can only
294 * happen at segment boundaries. A pointer in the code cache can be mapped to a segment
295 * by calling segment_for(addr). Each time memory is requested from the code cache,
296 * the segmap is updated accordingly. See the following example, which illustrates the
297 * state of code cache and the segment map: (seg -> segment, nm ->nmethod)
298 *
299 * code cache segmap
300 * ----------- ---------
301 * seg 1 | nm 1 | -> | 0 |
302 * seg 2 | nm 1 | -> | 1 |
303 * ... | nm 1 | -> | .. |
304 * seg m | nm 2 | -> | 0 |
305 * seg m+1 | nm 2 | -> | 1 |
306 * ... | nm 2 | -> | 2 |
307 * ... | nm 2 | -> | .. |
308 * ... | nm 2 | -> | 0xFE |
309 * seg m+n | nm 2 | -> | 1 |
310 * ... | nm 2 | -> | |
311 *
312 * A value of '0' in the segmap indicates that this segment contains the beginning of
313 * an nmethod. Let's walk through a simple example: If we want to find the start of
314 * an nmethod that falls into seg 2, we read the value of the segmap[2]. The value
315 * is an offset that points to the segment that contains the start of the nmethod.
316 * Another example: If we want to get the start of nm 2, and we happen to get a pointer
317 * that points to seg m+n, we first read seg[n+m], which returns '1'. So we have to
318 * do one more read of the segmap[m+n-1] to finally get the segment header.
319 */
320 void* CodeHeap::find_start(void* p) const {
321 if (!contains(p)) {
322 return NULL;
323 }
324 size_t seg_idx = segment_for(p);
325 address seg_map = (address)_segmap.low();
326 if (is_segment_unused(seg_map[seg_idx])) {
327 return NULL;
328 }
329 while (seg_map[seg_idx] > 0) {
330 seg_idx -= (int)seg_map[seg_idx];
331 }
332
333 HeapBlock* h = block_at(seg_idx);
334 if (h->free()) {
335 return NULL;
336 }
337 return h->allocated_space();
338 }
339
340 CodeBlob* CodeHeap::find_blob_unsafe(void* start) const {
341 CodeBlob* result = (CodeBlob*)CodeHeap::find_start(start);
342 if (result != NULL && result->blob_contains((address)start)) {
343 return result;
344 }
345 return NULL;
346 }
347
348 size_t CodeHeap::alignment_unit() const {
349 // this will be a power of two
350 return _segment_size;
351 }
352
353
354 size_t CodeHeap::alignment_offset() const {
355 // The lowest address in any allocated block will be
356 // equal to alignment_offset (mod alignment_unit).
357 return sizeof(HeapBlock) & (_segment_size - 1);
358 }
359
360 // Returns the current block if available and used.
361 // If not, it returns the subsequent block (if available), NULL otherwise.
362 // Free blocks are merged, therefore there is at most one free block
363 // between two used ones. As a result, the subsequent block (if available) is
364 // guaranteed to be used.
365 void* CodeHeap::next_used(HeapBlock* b) const {
366 if (b != NULL && b->free()) b = next_block(b);
367 assert(b == NULL || !b->free(), "must be in use or at end of heap");
368 return (b == NULL) ? NULL : b->allocated_space();
369 }
370
371 // Returns the first used HeapBlock
372 HeapBlock* CodeHeap::first_block() const {
373 if (_next_segment > 0)
374 return block_at(0);
375 return NULL;
376 }
377
378 HeapBlock* CodeHeap::block_start(void* q) const {
379 HeapBlock* b = (HeapBlock*)find_start(q);
380 if (b == NULL) return NULL;
381 return b - 1;
382 }
383
384 // Returns the next Heap block an offset into one
385 HeapBlock* CodeHeap::next_block(HeapBlock *b) const {
386 if (b == NULL) return NULL;
387 size_t i = segment_for(b) + b->length();
388 if (i < _next_segment)
389 return block_at(i);
390 return NULL;
391 }
392
393
394 // Returns current capacity
395 size_t CodeHeap::capacity() const {
396 return _memory.committed_size();
397 }
398
399 size_t CodeHeap::max_capacity() const {
400 return _memory.reserved_size();
401 }
402
403 int CodeHeap::allocated_segments() const {
404 return (int)_next_segment;
405 }
406
407 size_t CodeHeap::allocated_capacity() const {
408 // size of used heap - size on freelist
409 return segments_to_size(_next_segment - _freelist_segments);
410 }
411
412 // Returns size of the unallocated heap block
413 size_t CodeHeap::heap_unallocated_capacity() const {
414 // Total number of segments - number currently used
415 return segments_to_size(_number_of_reserved_segments - _next_segment);
416 }
417
418 // Free list management
419
420 FreeBlock* CodeHeap::following_block(FreeBlock *b) {
421 return (FreeBlock*)(((address)b) + _segment_size * b->length());
422 }
423
424 // Inserts block b after a
425 void CodeHeap::insert_after(FreeBlock* a, FreeBlock* b) {
426 assert(a != NULL && b != NULL, "must be real pointers");
427
428 // Link b into the list after a
429 b->set_link(a->link());
430 a->set_link(b);
431
432 // See if we can merge blocks
433 merge_right(b); // Try to make b bigger
434 merge_right(a); // Try to make a include b
435 }
436
437 // Try to merge this block with the following block
438 bool CodeHeap::merge_right(FreeBlock* a) {
439 assert(a->free(), "must be a free block");
440 if (following_block(a) == a->link()) {
441 assert(a->link() != NULL && a->link()->free(), "must be free too");
442 // Update block a to include the following block
443 a->set_length(a->length() + a->link()->length());
444 a->set_link(a->link()->link());
445 // Update find_start map
446 size_t beg = segment_for(a);
447 mark_segmap_as_used(beg, beg + a->length());
448 _freelist_length--;
449 return true;
450 }
451 return false;
452 }
453
454
455 void CodeHeap::add_to_freelist(HeapBlock* a) {
456 FreeBlock* b = (FreeBlock*)a;
457 _freelist_length++;
458
459 assert(b != _freelist, "cannot be removed twice");
460
461
462 // Mark as free and update free space count
463 _freelist_segments += b->length();
464 b->set_free();
465
466 // First element in list?
467 if (_freelist == NULL) {
468 b->set_link(NULL);
469 _freelist = b;
470 return;
471 }
472
473 // Since the freelist is ordered (smaller addresses -> larger addresses) and the
474 // element we want to insert into the freelist has a smaller address than the first
475 // element, we can simply add 'b' as the first element and we are done.
476 if (b < _freelist) {
477 // Insert first in list
478 b->set_link(_freelist);
479 _freelist = b;
480 merge_right(_freelist);
481 return;
482 }
483
484 // Scan for right place to put into list. List
485 // is sorted by increasing addresses
486 FreeBlock* prev = _freelist;
487 FreeBlock* cur = _freelist->link();
488 while(cur != NULL && cur < b) {
489 assert(prev < cur, "Freelist must be ordered");
490 prev = cur;
491 cur = cur->link();
492 }
493 assert((prev < b) && (cur == NULL || b < cur), "free-list must be ordered");
494 insert_after(prev, b);
495 }
496
497 /**
498 * Search freelist for an entry on the list with the best fit.
499 * @return NULL, if no one was found
500 */
501 HeapBlock* CodeHeap::search_freelist(size_t length) {
502 FreeBlock* found_block = NULL;
503 FreeBlock* found_prev = NULL;
504 size_t found_length = _next_segment; // max it out to begin with
505
506 HeapBlock* res = NULL;
507 FreeBlock* prev = NULL;
508 FreeBlock* cur = _freelist;
509
510 length = length < CodeCacheMinBlockLength ? CodeCacheMinBlockLength : length;
511
512 // Search for best-fitting block
513 while(cur != NULL) {
514 size_t cur_length = cur->length();
515 if (cur_length == length) {
516 // We have a perfect fit
517 found_block = cur;
518 found_prev = prev;
519 found_length = cur_length;
520 break;
521 } else if ((cur_length > length) && (cur_length < found_length)) {
522 // This is a new, closer fit. Remember block, its previous element, and its length
523 found_block = cur;
524 found_prev = prev;
525 found_length = cur_length;
526 }
527 // Next element in list
528 prev = cur;
529 cur = cur->link();
530 }
531
532 if (found_block == NULL) {
533 // None found
534 return NULL;
535 }
536
537 // Exact (or at least good enough) fit. Remove from list.
538 // Don't leave anything on the freelist smaller than CodeCacheMinBlockLength.
539 if (found_length - length < CodeCacheMinBlockLength) {
540 _freelist_length--;
541 length = found_length;
542 if (found_prev == NULL) {
543 assert(_freelist == found_block, "sanity check");
544 _freelist = _freelist->link();
545 } else {
546 assert((found_prev->link() == found_block), "sanity check");
547 // Unmap element
548 found_prev->set_link(found_block->link());
549 }
550 res = found_block;
551 } else {
552 // Truncate the free block and return the truncated part
553 // as new HeapBlock. The remaining free block does not
554 // need to be updated, except for it's length. Truncating
555 // the segment map does not invalidate the leading part.
556 res = split_block(found_block, found_length - length);
557 }
558
559 res->set_used();
560 _freelist_segments -= length;
561 return res;
562 }
563
564 //----------------------------------------------------------------------------
565 // Non-product code
566
567 #ifndef PRODUCT
568
569 void CodeHeap::print() {
570 tty->print_cr("The Heap");
571 }
572
573 void CodeHeap::verify() {
574 if (VerifyCodeCache) {
575 size_t len = 0;
576 int count = 0;
577 for(FreeBlock* b = _freelist; b != NULL; b = b->link()) {
578 len += b->length();
579 count++;
580 // Check if we have merged all free blocks
581 assert(merge_right(b) == false, "Missed merging opportunity");
582 }
583 // Verify that freelist contains the right amount of free space
584 assert(len == _freelist_segments, "wrong freelist");
585
586 for(HeapBlock* h = first_block(); h != NULL; h = next_block(h)) {
587 if (h->free()) count--;
588 }
589 // Verify that the freelist contains the same number of blocks
590 // than free blocks found on the full list.
591 assert(count == 0, "missing free blocks");
592
593 // Verify segment map marking.
594 // All allocated segments, no matter if in a free or used block,
595 // must be marked "in use".
596 address seg_map = (address)_segmap.low();
597 size_t nseg = 0;
598 for(HeapBlock* b = first_block(); b != NULL; b = next_block(b)) {
599 size_t seg1 = segment_for(b);
600 size_t segn = seg1 + b->length();
601 for (size_t i = seg1; i < segn; i++) {
602 nseg++;
603 if (is_segment_unused(seg_map[i])) {
604 warning("CodeHeap: unused segment. %d [%d..%d], %s block", (int)i, (int)seg1, (int)segn, b->free()? "free":"used");
605 }
606 }
607 }
608 if (nseg != _next_segment) {
609 warning("CodeHeap: segment count mismatch. found %d, expected %d.", (int)nseg, (int)_next_segment);
610 }
611
612 // Verify that the number of free blocks is not out of hand.
613 static int free_block_threshold = 10000;
614 if (count > free_block_threshold) {
615 warning("CodeHeap: # of free blocks > %d", free_block_threshold);
616 // Double the warning limit
617 free_block_threshold *= 2;
618 }
619 }
620 }
621
622 #endif