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() {
39 _number_of_committed_segments = 0;
40 _number_of_reserved_segments = 0;
41 _segment_size = 0;
42 _log2_segment_size = 0;
43 _next_segment = 0;
44 _freelist = NULL;
45 _freelist_segments = 0;
46 }
47
48
49 void CodeHeap::mark_segmap_as_free(size_t beg, size_t end) {
50 assert(0 <= beg && beg < _number_of_committed_segments, "interval begin out of bounds");
51 assert(beg < end && end <= _number_of_committed_segments, "interval end out of bounds");
52 // setup _segmap pointers for faster indexing
53 address p = (address)_segmap.low() + beg;
54 address q = (address)_segmap.low() + end;
55 // initialize interval
56 while (p < q) *p++ = free_sentinel;
57 }
58
59
60 void CodeHeap::mark_segmap_as_used(size_t beg, size_t end) {
61 assert(0 <= beg && beg < _number_of_committed_segments, "interval begin out of bounds");
62 assert(beg < end && end <= _number_of_committed_segments, "interval end out of bounds");
63 // setup _segmap pointers for faster indexing
64 address p = (address)_segmap.low() + beg;
65 address q = (address)_segmap.low() + end;
66 // initialize interval
67 int i = 0;
68 while (p < q) {
69 *p++ = i++;
70 if (i == free_sentinel) i = 1;
71 }
72 }
73
74
75 static size_t align_to_page_size(size_t size) {
76 const size_t alignment = (size_t)os::vm_page_size();
77 assert(is_power_of_2(alignment), "no kidding ???");
78 return (size + alignment - 1) & ~(alignment - 1);
79 }
80
81
82 void CodeHeap::on_code_mapping(char* base, size_t size) {
83 #ifdef LINUX
84 extern void linux_wrap_code(char* base, size_t size);
85 linux_wrap_code(base, size);
86 #endif
87 }
88
89
90 bool CodeHeap::reserve(size_t reserved_size, size_t committed_size,
91 size_t segment_size) {
92 assert(reserved_size >= committed_size, "reserved < committed");
93 assert(segment_size >= sizeof(FreeBlock), "segment size is too small");
94 assert(is_power_of_2(segment_size), "segment_size must be a power of 2");
95
96 _segment_size = segment_size;
97 _log2_segment_size = exact_log2(segment_size);
98
99 // Reserve and initialize space for _memory.
100 const size_t page_size = os::can_execute_large_page_memory() ?
101 os::page_size_for_region(committed_size, reserved_size, 8) :
102 os::vm_page_size();
103 const size_t granularity = os::vm_allocation_granularity();
104 const size_t r_align = MAX2(page_size, granularity);
105 const size_t r_size = align_size_up(reserved_size, r_align);
106 const size_t c_size = align_size_up(committed_size, page_size);
107
108 const size_t rs_align = page_size == (size_t) os::vm_page_size() ? 0 :
109 MAX2(page_size, granularity);
110 ReservedCodeSpace rs(r_size, rs_align, rs_align > 0);
111 os::trace_page_sizes("code heap", committed_size, reserved_size, page_size,
112 rs.base(), rs.size());
113 if (!_memory.initialize(rs, c_size)) {
114 return false;
115 }
116
117 on_code_mapping(_memory.low(), _memory.committed_size());
118 _number_of_committed_segments = size_to_segments(_memory.committed_size());
119 _number_of_reserved_segments = size_to_segments(_memory.reserved_size());
120 assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking");
121 const size_t reserved_segments_alignment = MAX2((size_t)os::vm_page_size(), granularity);
122 const size_t reserved_segments_size = align_size_up(_number_of_reserved_segments, reserved_segments_alignment);
123 const size_t committed_segments_size = align_to_page_size(_number_of_committed_segments);
124
125 // reserve space for _segmap
126 if (!_segmap.initialize(reserved_segments_size, committed_segments_size)) {
127 return false;
128 }
129
130 MemTracker::record_virtual_memory_type((address)_segmap.low_boundary(), mtCode);
131
132 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "could not commit enough space for segment map");
133 assert(_segmap.reserved_size() >= (size_t) _number_of_reserved_segments , "could not reserve enough space for segment map");
134 assert(_segmap.reserved_size() >= _segmap.committed_size() , "just checking");
135
136 // initialize remaining instance variables
137 clear();
138 return true;
139 }
140
141
142 bool CodeHeap::expand_by(size_t size) {
143 // expand _memory space
144 size_t dm = align_to_page_size(_memory.committed_size() + size) - _memory.committed_size();
145 if (dm > 0) {
146 char* base = _memory.low() + _memory.committed_size();
147 if (!_memory.expand_by(dm)) return false;
148 on_code_mapping(base, dm);
149 size_t i = _number_of_committed_segments;
150 _number_of_committed_segments = size_to_segments(_memory.committed_size());
151 assert(_number_of_reserved_segments == size_to_segments(_memory.reserved_size()), "number of reserved segments should not change");
152 assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking");
153 // expand _segmap space
154 size_t ds = align_to_page_size(_number_of_committed_segments) - _segmap.committed_size();
155 if ((ds > 0) && !_segmap.expand_by(ds)) {
156 return false;
157 }
158 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "just checking");
159 // initialize additional segmap entries
160 mark_segmap_as_free(i, _number_of_committed_segments);
161 }
162 return true;
163 }
164
165 void CodeHeap::clear() {
166 _next_segment = 0;
167 mark_segmap_as_free(0, _number_of_committed_segments);
168 }
169
170
171 void* CodeHeap::allocate(size_t instance_size, bool is_critical) {
172 size_t number_of_segments = size_to_segments(instance_size + header_size());
173 assert(segments_to_size(number_of_segments) >= sizeof(FreeBlock), "not enough room for FreeList");
174
175 // First check if we can satisfy request from freelist
176 NOT_PRODUCT(verify());
177 HeapBlock* block = search_freelist(number_of_segments, is_critical);
178 NOT_PRODUCT(verify());
179
180 if (block != NULL) {
181 assert(block->length() >= number_of_segments && block->length() < number_of_segments + CodeCacheMinBlockLength, "sanity check");
182 assert(!block->free(), "must be marked free");
183 DEBUG_ONLY(memset((void*)block->allocated_space(), badCodeHeapNewVal, instance_size));
184 return block->allocated_space();
185 }
186
187 // Ensure minimum size for allocation to the heap.
188 number_of_segments = MAX2((int)CodeCacheMinBlockLength, (int)number_of_segments);
189
190 if (!is_critical) {
191 // Make sure the allocation fits in the unallocated heap without using
192 // the CodeCacheMimimumFreeSpace that is reserved for critical allocations.
193 if (segments_to_size(number_of_segments) > (heap_unallocated_capacity() - CodeCacheMinimumFreeSpace)) {
194 // Fail allocation
195 return NULL;
196 }
197 }
198
199 if (_next_segment + number_of_segments <= _number_of_committed_segments) {
200 mark_segmap_as_used(_next_segment, _next_segment + number_of_segments);
201 HeapBlock* b = block_at(_next_segment);
202 b->initialize(number_of_segments);
203 _next_segment += number_of_segments;
204 DEBUG_ONLY(memset((void *)b->allocated_space(), badCodeHeapNewVal, instance_size));
205 return b->allocated_space();
206 } else {
207 return NULL;
208 }
209 }
210
211
212 void CodeHeap::deallocate(void* p) {
213 assert(p == find_start(p), "illegal deallocation");
214 // Find start of HeapBlock
215 HeapBlock* b = (((HeapBlock *)p) - 1);
216 assert(b->allocated_space() == p, "sanity check");
217 DEBUG_ONLY(memset((void *)b->allocated_space(), badCodeHeapFreeVal,
218 segments_to_size(b->length()) - sizeof(HeapBlock)));
219 add_to_freelist(b);
220 NOT_PRODUCT(verify());
221 }
222
223 /**
224 * Uses segment map to find the the start (header) of a nmethod. This works as follows:
225 * The memory of the code cache is divided into 'segments'. The size of a segment is
226 * determined by -XX:CodeCacheSegmentSize=XX. Allocation in the code cache can only
227 * happen at segment boundaries. A pointer in the code cache can be mapped to a segment
228 * by calling segment_for(addr). Each time memory is requested from the code cache,
229 * the segmap is updated accordingly. See the following example, which illustrates the
230 * state of code cache and the segment map: (seg -> segment, nm ->nmethod)
231 *
232 * code cache segmap
233 * ----------- ---------
234 * seg 1 | nm 1 | -> | 0 |
235 * seg 2 | nm 1 | -> | 1 |
236 * ... | nm 1 | -> | .. |
237 * seg m | nm 2 | -> | 0 |
238 * seg m+1 | nm 2 | -> | 1 |
239 * ... | nm 2 | -> | 2 |
240 * ... | nm 2 | -> | .. |
241 * ... | nm 2 | -> | 0xFE |
242 * seg m+n | nm 2 | -> | 1 |
243 * ... | nm 2 | -> | |
244 *
245 * A value of '0' in the segmap indicates that this segment contains the beginning of
246 * an nmethod. Let's walk through a simple example: If we want to find the start of
247 * an nmethod that falls into seg 2, we read the value of the segmap[2]. The value
248 * is an offset that points to the segment that contains the start of the nmethod.
249 * Another example: If we want to get the start of nm 2, and we happen to get a pointer
250 * that points to seg m+n, we first read seg[n+m], which returns '1'. So we have to
251 * do one more read of the segmap[m+n-1] to finally get the segment header.
252 */
253 void* CodeHeap::find_start(void* p) const {
254 if (!contains(p)) {
255 return NULL;
256 }
257 size_t seg_idx = segment_for(p);
258 address seg_map = (address)_segmap.low();
259 if (is_segment_unused(seg_map[seg_idx])) {
260 return NULL;
261 }
262 while (seg_map[seg_idx] > 0) {
263 seg_idx -= (int)seg_map[seg_idx];
264 }
265
266 HeapBlock* h = block_at(seg_idx);
267 if (h->free()) {
268 return NULL;
269 }
270 return h->allocated_space();
271 }
272
273
274 size_t CodeHeap::alignment_unit() const {
275 // this will be a power of two
276 return _segment_size;
277 }
278
279
280 size_t CodeHeap::alignment_offset() const {
281 // The lowest address in any allocated block will be
282 // equal to alignment_offset (mod alignment_unit).
283 return sizeof(HeapBlock) & (_segment_size - 1);
284 }
285
286 // Finds the next free heapblock. If the current one is free, that it returned
287 void* CodeHeap::next_free(HeapBlock* b) const {
288 // Since free blocks are merged, there is max. on free block
289 // between two used ones
290 if (b != NULL && b->free()) b = next_block(b);
291 assert(b == NULL || !b->free(), "must be in use or at end of heap");
292 return (b == NULL) ? NULL : b->allocated_space();
293 }
294
295 // Returns the first used HeapBlock
296 HeapBlock* CodeHeap::first_block() const {
297 if (_next_segment > 0)
298 return block_at(0);
299 return NULL;
300 }
301
302 HeapBlock* CodeHeap::block_start(void* q) const {
303 HeapBlock* b = (HeapBlock*)find_start(q);
304 if (b == NULL) return NULL;
305 return b - 1;
306 }
307
308 // Returns the next Heap block an offset into one
309 HeapBlock* CodeHeap::next_block(HeapBlock *b) const {
310 if (b == NULL) return NULL;
311 size_t i = segment_for(b) + b->length();
312 if (i < _next_segment)
313 return block_at(i);
314 return NULL;
315 }
316
317
318 // Returns current capacity
319 size_t CodeHeap::capacity() const {
320 return _memory.committed_size();
321 }
322
323 size_t CodeHeap::max_capacity() const {
324 return _memory.reserved_size();
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 return true;
369 }
370 return false;
371 }
372
373
374 void CodeHeap::add_to_freelist(HeapBlock* a) {
375 FreeBlock* b = (FreeBlock*)a;
376 assert(b != _freelist, "cannot be removed twice");
377
378 // Mark as free and update free space count
379 _freelist_segments += b->length();
380 b->set_free();
381
382 // First element in list?
383 if (_freelist == NULL) {
384 _freelist = b;
385 b->set_link(NULL);
386 return;
387 }
388
389 // Since the freelist is ordered (smaller->larger) and the element we want to insert
390 // into the freelist is smaller than the first element, we can simply add 'b' as the
391 // first element and we are done.
392 if (b < _freelist) {
393 // Insert first in list
394 b->set_link(_freelist);
395 _freelist = b;
396 merge_right(_freelist);
397 return;
398 }
399
400 // Scan for right place to put into list. List
401 // is sorted by increasing addresses
402 FreeBlock* prev = _freelist;
403 FreeBlock* cur = _freelist->link();
404 while(cur != NULL && cur < b) {
405 assert(prev < cur, "Freelist must be ordered");
406 prev = cur;
407 cur = cur->link();
408 }
409 assert((prev < b) && (cur == NULL || b < cur), "free-list must be ordered");
410 insert_after(prev, b);
411 }
412
413 /**
414 * Search freelist for an entry on the list with the best fit.
415 * @return NULL, if no one was found
416 */
417 FreeBlock* CodeHeap::search_freelist(size_t length, bool is_critical) {
418 FreeBlock* best_block = NULL;
419 FreeBlock* best_prev = NULL;
420 size_t best_length = 0;
421
422 FreeBlock* prev = NULL;
423 FreeBlock* cur = _freelist;
424 const size_t critical_boundary = (size_t)high_boundary() - CodeCacheMinimumFreeSpace;
425
426 // Search for smallest block which is bigger than length
427 while(cur != NULL) {
428 size_t l = cur->length();
429 if (l >= length && (best_block == NULL || l < best_length )) {
430 // Non critical allocations are not allowed to use the last part of the code heap.
431 // Make sure the end of the allocation doesn't cross into the last part of the code heap.
432 if (!is_critical && (((size_t)cur + length) > critical_boundary)) {
433 // The freelist is sorted by address - if one fails, all consecutive will also fail.
434 break;
435 }
436
437 // Remember best block, its previous element, and its length
438 best_block = cur;
439 best_prev = prev;
440 best_length = best_block->length();
441
442 // Found best fit, since we are not allowed to have less than CodeCacheMinBlockLength number of
443 // free segments.
444 if ((best_length - length) < CodeCacheMinBlockLength) {
445 break;
446 }
447 }
448
449 // Next element in list
450 prev = cur;
451 cur = cur->link();
452 }
453
454 if (best_block == NULL) {
455 // None found
456 return NULL;
457 }
458
459 // Exact (or at least good enough) fit. Remove from list.
460 // Don't leave anything on the freelist smaller than CodeCacheMinBlockLength.
461 if (best_length < length + CodeCacheMinBlockLength) {
462 length = best_length;
463 if (best_prev == NULL) {
464 assert(_freelist == best_block, "sanity check");
465 _freelist = _freelist->link();
466 } else {
467 assert((best_prev->link() == best_block), "sanity check");
468 // Unmap element
469 best_prev->set_link(best_block->link());
470 }
471 } else {
472 // Truncate block and return a pointer to the following block
473 best_block->set_length(best_length - length);
474 best_block = following_block(best_block);
475 // Set used bit and length on new block
476 size_t beg = segment_for(best_block);
477 mark_segmap_as_used(beg, beg + length);
478 best_block->set_length(length);
479 }
480
481 best_block->set_used();
482 _freelist_segments -= length;
483 return best_block;
484 }
485
486 //----------------------------------------------------------------------------
487 // Non-product code
488
489 #ifndef PRODUCT
490
491 void CodeHeap::print() {
492 tty->print_cr("The Heap");
493 }
494
495 void CodeHeap::verify() {
496 if (VerifyCodeCache) {
497 size_t len = 0;
498 int count = 0;
499 for(FreeBlock* b = _freelist; b != NULL; b = b->link()) {
500 len += b->length();
501 count++;
502 // Check if we have merged all free blocks
503 assert(merge_right(b) == false, "Missed merging opportunity");
504 }
505 // Verify that freelist contains the right amount of free space
506 assert(len == _freelist_segments, "wrong freelist");
507
508 for(HeapBlock* h = first_block(); h != NULL; h = next_block(h)) {
509 if (h->free()) count--;
510 }
511 // Verify that the freelist contains the same number of blocks
512 // than free blocks found on the full list.
513 assert(count == 0, "missing free blocks");
514
515 // Verify that the number of free blocks is not out of hand.
516 static int free_block_threshold = 10000;
517 if (count > free_block_threshold) {
518 warning("CodeHeap: # of free blocks > %d", free_block_threshold);
519 // Double the warning limit
520 free_block_threshold *= 2;
521 }
522 }
523 }
524
525 #endif