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++ = 0xFF;
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 == 0xFF) 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,
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 void CodeHeap::release() {
143 Unimplemented();
144 }
145
146
147 bool CodeHeap::expand_by(size_t size) {
148 // expand _memory space
149 size_t dm = align_to_page_size(_memory.committed_size() + size) - _memory.committed_size();
150 if (dm > 0) {
151 char* base = _memory.low() + _memory.committed_size();
152 if (!_memory.expand_by(dm)) return false;
153 on_code_mapping(base, dm);
154 size_t i = _number_of_committed_segments;
155 _number_of_committed_segments = size_to_segments(_memory.committed_size());
156 assert(_number_of_reserved_segments == size_to_segments(_memory.reserved_size()), "number of reserved segments should not change");
157 assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking");
158 // expand _segmap space
159 size_t ds = align_to_page_size(_number_of_committed_segments) - _segmap.committed_size();
160 if (ds > 0) {
161 if (!_segmap.expand_by(ds)) return false;
162 }
163 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "just checking");
164 // initialize additional segmap entries
165 mark_segmap_as_free(i, _number_of_committed_segments);
166 }
167 return true;
168 }
169
170
171 void CodeHeap::shrink_by(size_t size) {
172 Unimplemented();
173 }
174
175
176 void CodeHeap::clear() {
177 _next_segment = 0;
178 mark_segmap_as_free(0, _number_of_committed_segments);
179 }
180
181
182 void* CodeHeap::allocate(size_t instance_size, bool is_critical) {
183 size_t number_of_segments = size_to_segments(instance_size + sizeof(HeapBlock));
184 assert(segments_to_size(number_of_segments) >= sizeof(FreeBlock), "not enough room for FreeList");
185
186 // First check if we can satify request from freelist
187 debug_only(verify());
188 HeapBlock* block = search_freelist(number_of_segments, is_critical);
189 debug_only(if (VerifyCodeCacheOften) verify());
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 #ifdef ASSERT
194 memset((void *)block->allocated_space(), badCodeHeapNewVal, instance_size);
195 #endif
196 return block->allocated_space();
197 }
198
199 // Ensure minimum size for allocation to the heap.
200 if (number_of_segments < CodeCacheMinBlockLength) {
201 number_of_segments = CodeCacheMinBlockLength;
202 }
203
204 if (!is_critical) {
205 // Make sure the allocation fits in the unallocated heap without using
206 // the CodeCacheMimimumFreeSpace that is reserved for critical allocations.
207 if (segments_to_size(number_of_segments) > (heap_unallocated_capacity() - CodeCacheMinimumFreeSpace)) {
208 // Fail allocation
209 return NULL;
210 }
211 }
212
213 if (_next_segment + number_of_segments <= _number_of_committed_segments) {
214 mark_segmap_as_used(_next_segment, _next_segment + number_of_segments);
215 HeapBlock* b = block_at(_next_segment);
216 b->initialize(number_of_segments);
217 _next_segment += number_of_segments;
218 #ifdef ASSERT
219 memset((void *)b->allocated_space(), badCodeHeapNewVal, instance_size);
220 #endif
221 return b->allocated_space();
222 } else {
223 return NULL;
224 }
225 }
226
227
228 void CodeHeap::deallocate(void* p) {
229 assert(p == find_start(p), "illegal deallocation");
230 // Find start of HeapBlock
231 HeapBlock* b = (((HeapBlock *)p) - 1);
232 assert(b->allocated_space() == p, "sanity check");
233 #ifdef ASSERT
234 memset((void *)b->allocated_space(),
235 badCodeHeapFreeVal,
236 segments_to_size(b->length()) - sizeof(HeapBlock));
237 #endif
238 add_to_freelist(b);
239
240 debug_only(if (VerifyCodeCacheOften) verify());
241 }
242
243
244 void* CodeHeap::find_start(void* p) const {
245 if (!contains(p)) {
246 return NULL;
247 }
248 size_t i = segment_for(p);
249 address b = (address)_segmap.low();
250 if (b[i] == 0xFF) {
251 return NULL;
252 }
253 while (b[i] > 0) i -= (int)b[i];
254 HeapBlock* h = block_at(i);
255 if (h->free()) {
256 return NULL;
257 }
258 return h->allocated_space();
259 }
260
261
262 size_t CodeHeap::alignment_unit() const {
263 // this will be a power of two
264 return _segment_size;
265 }
266
267
268 size_t CodeHeap::alignment_offset() const {
269 // The lowest address in any allocated block will be
270 // equal to alignment_offset (mod alignment_unit).
271 return sizeof(HeapBlock) & (_segment_size - 1);
272 }
273
274 // Finds the next free heapblock. If the current one is free, that it returned
275 void* CodeHeap::next_free(HeapBlock *b) const {
276 // Since free blocks are merged, there is max. on free block
277 // between two used ones
278 if (b != NULL && b->free()) b = next_block(b);
279 assert(b == NULL || !b->free(), "must be in use or at end of heap");
280 return (b == NULL) ? NULL : b->allocated_space();
281 }
282
283 // Returns the first used HeapBlock
284 HeapBlock* CodeHeap::first_block() const {
285 if (_next_segment > 0)
286 return block_at(0);
287 return NULL;
288 }
289
290 HeapBlock *CodeHeap::block_start(void *q) const {
291 HeapBlock* b = (HeapBlock*)find_start(q);
292 if (b == NULL) return NULL;
293 return b - 1;
294 }
295
296 // Returns the next Heap block an offset into one
297 HeapBlock* CodeHeap::next_block(HeapBlock *b) const {
298 if (b == NULL) return NULL;
299 size_t i = segment_for(b) + b->length();
300 if (i < _next_segment)
301 return block_at(i);
302 return NULL;
303 }
304
305
306 // Returns current capacity
307 size_t CodeHeap::capacity() const {
308 return _memory.committed_size();
309 }
310
311 size_t CodeHeap::max_capacity() const {
312 return _memory.reserved_size();
313 }
314
315 size_t CodeHeap::allocated_capacity() const {
316 // size of used heap - size on freelist
317 return segments_to_size(_next_segment - _freelist_segments);
318 }
319
320 // Returns size of the unallocated heap block
321 size_t CodeHeap::heap_unallocated_capacity() const {
322 // Total number of segments - number currently used
323 return segments_to_size(_number_of_reserved_segments - _next_segment);
324 }
325
326 // Free list management
327
328 FreeBlock *CodeHeap::following_block(FreeBlock *b) {
329 return (FreeBlock*)(((address)b) + _segment_size * b->length());
330 }
331
332 // Inserts block b after a
333 void CodeHeap::insert_after(FreeBlock* a, FreeBlock* b) {
334 assert(a != NULL && b != NULL, "must be real pointers");
335
336 // Link b into the list after a
337 b->set_link(a->link());
338 a->set_link(b);
339
340 // See if we can merge blocks
341 merge_right(b); // Try to make b bigger
342 merge_right(a); // Try to make a include b
343 }
344
345 // Try to merge this block with the following block
346 void CodeHeap::merge_right(FreeBlock *a) {
347 assert(a->free(), "must be a free block");
348 if (following_block(a) == a->link()) {
349 assert(a->link() != NULL && a->link()->free(), "must be free too");
350 // Update block a to include the following block
351 a->set_length(a->length() + a->link()->length());
352 a->set_link(a->link()->link());
353 // Update find_start map
354 size_t beg = segment_for(a);
355 mark_segmap_as_used(beg, beg + a->length());
356 }
357 }
358
359 void CodeHeap::add_to_freelist(HeapBlock *a) {
360 FreeBlock* b = (FreeBlock*)a;
361 assert(b != _freelist, "cannot be removed twice");
362
363 // Mark as free and update free space count
364 _freelist_segments += b->length();
365 b->set_free();
366
367 // First element in list?
368 if (_freelist == NULL) {
369 _freelist = b;
370 b->set_link(NULL);
371 return;
372 }
373
374 // Scan for right place to put into list. List
375 // is sorted by increasing addresseses
376 FreeBlock* prev = NULL;
377 FreeBlock* cur = _freelist;
378 while(cur != NULL && cur < b) {
379 assert(prev == NULL || prev < cur, "must be ordered");
380 prev = cur;
381 cur = cur->link();
382 }
383
384 assert( (prev == NULL && b < _freelist) ||
385 (prev < b && (cur == NULL || b < cur)), "list must be ordered");
386
387 if (prev == NULL) {
388 // Insert first in list
389 b->set_link(_freelist);
390 _freelist = b;
391 merge_right(_freelist);
392 } else {
393 insert_after(prev, b);
394 }
395 }
396
397 // Search freelist for an entry on the list with the best fit
398 // Return NULL if no one was found
399 FreeBlock* CodeHeap::search_freelist(size_t length, bool is_critical) {
400 FreeBlock *best_block = NULL;
401 FreeBlock *best_prev = NULL;
402 size_t best_length = 0;
403
404 // Search for smallest block which is bigger than length
405 FreeBlock *prev = NULL;
406 FreeBlock *cur = _freelist;
407 while(cur != NULL) {
408 size_t l = cur->length();
409 if (l >= length && (best_block == NULL || best_length > l)) {
410
411 // Non critical allocations are not allowed to use the last part of the code heap.
412 if (!is_critical) {
413 // Make sure the end of the allocation doesn't cross into the last part of the code heap
414 if (((size_t)cur + length) > ((size_t)high_boundary() - CodeCacheMinimumFreeSpace)) {
415 // the freelist is sorted by address - if one fails, all consecutive will also fail.
416 break;
417 }
418 }
419
420 // Remember best block, its previous element, and its length
421 best_block = cur;
422 best_prev = prev;
423 best_length = best_block->length();
424 }
425
426 // Next element in list
427 prev = cur;
428 cur = cur->link();
429 }
430
431 if (best_block == NULL) {
432 // None found
433 return NULL;
434 }
435
436 assert((best_prev == NULL && _freelist == best_block ) ||
437 (best_prev != NULL && best_prev->link() == best_block), "sanity check");
438
439 // Exact (or at least good enough) fit. Remove from list.
440 // Don't leave anything on the freelist smaller than CodeCacheMinBlockLength.
441 if (best_length < length + CodeCacheMinBlockLength) {
442 length = best_length;
443 if (best_prev == NULL) {
444 assert(_freelist == best_block, "sanity check");
445 _freelist = _freelist->link();
446 } else {
447 // Unmap element
448 best_prev->set_link(best_block->link());
449 }
450 } else {
451 // Truncate block and return a pointer to the following block
452 best_block->set_length(best_length - length);
453 best_block = following_block(best_block);
454 // Set used bit and length on new block
455 size_t beg = segment_for(best_block);
456 mark_segmap_as_used(beg, beg + length);
457 best_block->set_length(length);
458 }
459
460 best_block->set_used();
461 _freelist_segments -= length;
462 return best_block;
463 }
464
465 //----------------------------------------------------------------------------
466 // Non-product code
467
468 #ifndef PRODUCT
469
470 void CodeHeap::print() {
471 tty->print_cr("The Heap");
472 }
473
474 #endif
475
476 void CodeHeap::verify() {
477 // Count the number of blocks on the freelist, and the amount of space
478 // represented.
479 int count = 0;
480 size_t len = 0;
481 for(FreeBlock* b = _freelist; b != NULL; b = b->link()) {
482 len += b->length();
483 count++;
484 }
485
486 // Verify that freelist contains the right amount of free space
487 // guarantee(len == _freelist_segments, "wrong freelist");
488
489 // Verify that the number of free blocks is not out of hand.
490 static int free_block_threshold = 10000;
491 if (count > free_block_threshold) {
492 warning("CodeHeap: # of free blocks > %d", free_block_threshold);
493 // Double the warning limit
494 free_block_threshold *= 2;
495 }
496
497 // Verify that the freelist contains the same number of free blocks that is
498 // found on the full list.
499 for(HeapBlock *h = first_block(); h != NULL; h = next_block(h)) {
500 if (h->free()) count--;
501 }
502 // guarantee(count == 0, "missing free blocks");
503 }
|
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 _freelist_length = 0;
47 }
48
49
50 void CodeHeap::mark_segmap_as_free(size_t beg, size_t end) {
51 assert(0 <= beg && beg < _number_of_committed_segments, "interval begin out of bounds");
52 assert(beg < end && end <= _number_of_committed_segments, "interval end out of bounds");
53 // setup _segmap pointers for faster indexing
54 address p = (address)_segmap.low() + beg;
55 address q = (address)_segmap.low() + end;
56 // initialize interval
57 while (p < q) *p++ = free_sentinel;
58 }
59
60
61 void CodeHeap::mark_segmap_as_used(size_t beg, size_t end) {
62 assert(0 <= beg && beg < _number_of_committed_segments, "interval begin out of bounds");
63 assert(beg < end && end <= _number_of_committed_segments, "interval end out of bounds");
64 // setup _segmap pointers for faster indexing
65 address p = (address)_segmap.low() + beg;
66 address q = (address)_segmap.low() + end;
67 // initialize interval
68 int i = 0;
69 while (p < q) {
70 *p++ = i++;
71 if (i == free_sentinel) i = 1;
72 }
73 }
74
75
76 static size_t align_to_page_size(size_t size) {
77 const size_t alignment = (size_t)os::vm_page_size();
78 assert(is_power_of_2(alignment), "no kidding ???");
79 return (size + alignment - 1) & ~(alignment - 1);
80 }
81
82
83 void CodeHeap::on_code_mapping(char* base, size_t size) {
84 #ifdef LINUX
85 extern void linux_wrap_code(char* base, size_t size);
86 linux_wrap_code(base, size);
87 #endif
88 }
89
90
91 bool CodeHeap::reserve(size_t reserved_size, size_t committed_size,
123 const size_t reserved_segments_size = align_size_up(_number_of_reserved_segments, reserved_segments_alignment);
124 const size_t committed_segments_size = align_to_page_size(_number_of_committed_segments);
125
126 // reserve space for _segmap
127 if (!_segmap.initialize(reserved_segments_size, committed_segments_size)) {
128 return false;
129 }
130
131 MemTracker::record_virtual_memory_type((address)_segmap.low_boundary(), mtCode);
132
133 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "could not commit enough space for segment map");
134 assert(_segmap.reserved_size() >= (size_t) _number_of_reserved_segments , "could not reserve enough space for segment map");
135 assert(_segmap.reserved_size() >= _segmap.committed_size() , "just checking");
136
137 // initialize remaining instance variables
138 clear();
139 return true;
140 }
141
142
143 bool CodeHeap::expand_by(size_t size) {
144 // expand _memory space
145 size_t dm = align_to_page_size(_memory.committed_size() + size) - _memory.committed_size();
146 if (dm > 0) {
147 char* base = _memory.low() + _memory.committed_size();
148 if (!_memory.expand_by(dm)) return false;
149 on_code_mapping(base, dm);
150 size_t i = _number_of_committed_segments;
151 _number_of_committed_segments = size_to_segments(_memory.committed_size());
152 assert(_number_of_reserved_segments == size_to_segments(_memory.reserved_size()), "number of reserved segments should not change");
153 assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking");
154 // expand _segmap space
155 size_t ds = align_to_page_size(_number_of_committed_segments) - _segmap.committed_size();
156 if ((ds > 0) && !_segmap.expand_by(ds)) {
157 return false;
158 }
159 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "just checking");
160 // initialize additional segmap entries
161 mark_segmap_as_free(i, _number_of_committed_segments);
162 }
163 return true;
164 }
165
166 void CodeHeap::clear() {
167 _next_segment = 0;
168 mark_segmap_as_free(0, _number_of_committed_segments);
169 }
170
171
172 void* CodeHeap::allocate(size_t instance_size, bool is_critical) {
173 size_t number_of_segments = size_to_segments(instance_size + header_size());
174 assert(segments_to_size(number_of_segments) >= sizeof(FreeBlock), "not enough room for FreeList");
175
176 // First check if we can satisfy request from freelist
177 NOT_PRODUCT(verify());
178 HeapBlock* block = search_freelist(number_of_segments, is_critical);
179 NOT_PRODUCT(verify());
180
181 if (block != NULL) {
182 assert(block->length() >= number_of_segments && block->length() < number_of_segments + CodeCacheMinBlockLength, "sanity check");
183 assert(!block->free(), "must be marked free");
184 DEBUG_ONLY(memset((void*)block->allocated_space(), badCodeHeapNewVal, instance_size));
185 return block->allocated_space();
186 }
187
188 // Ensure minimum size for allocation to the heap.
189 number_of_segments = MAX2((int)CodeCacheMinBlockLength, (int)number_of_segments);
190
191 if (!is_critical) {
192 // Make sure the allocation fits in the unallocated heap without using
193 // the CodeCacheMimimumFreeSpace that is reserved for critical allocations.
194 if (segments_to_size(number_of_segments) > (heap_unallocated_capacity() - CodeCacheMinimumFreeSpace)) {
195 // Fail allocation
196 return NULL;
197 }
198 }
199
200 if (_next_segment + number_of_segments <= _number_of_committed_segments) {
201 mark_segmap_as_used(_next_segment, _next_segment + number_of_segments);
202 HeapBlock* b = block_at(_next_segment);
203 b->initialize(number_of_segments);
204 _next_segment += number_of_segments;
205 DEBUG_ONLY(memset((void *)b->allocated_space(), badCodeHeapNewVal, instance_size));
206 return b->allocated_space();
207 } else {
208 return NULL;
209 }
210 }
211
212
213 void CodeHeap::deallocate(void* p) {
214 assert(p == find_start(p), "illegal deallocation");
215 // Find start of HeapBlock
216 HeapBlock* b = (((HeapBlock *)p) - 1);
217 assert(b->allocated_space() == p, "sanity check");
218 DEBUG_ONLY(memset((void *)b->allocated_space(), badCodeHeapFreeVal,
219 segments_to_size(b->length()) - sizeof(HeapBlock)));
220 add_to_freelist(b);
221 NOT_PRODUCT(verify());
222 }
223
224 /**
225 * Uses segment map to find the the start (header) of a nmethod. This works as follows:
226 * The memory of the code cache is divided into 'segments'. The size of a segment is
227 * determined by -XX:CodeCacheSegmentSize=XX. Allocation in the code cache can only
228 * happen at segment boundaries. A pointer in the code cache can be mapped to a segment
229 * by calling segment_for(addr). Each time memory is requested from the code cache,
230 * the segmap is updated accordingly. See the following example, which illustrates the
231 * state of code cache and the segment map: (seg -> segment, nm ->nmethod)
232 *
233 * code cache segmap
234 * ----------- ---------
235 * seg 1 | nm 1 | -> | 0 |
236 * seg 2 | nm 1 | -> | 1 |
237 * ... | nm 1 | -> | .. |
238 * seg m | nm 2 | -> | 0 |
239 * seg m+1 | nm 2 | -> | 1 |
240 * ... | nm 2 | -> | 2 |
241 * ... | nm 2 | -> | .. |
242 * ... | nm 2 | -> | 0xFE |
243 * seg m+n | nm 2 | -> | 1 |
244 * ... | nm 2 | -> | |
245 *
246 * A value of '0' in the segmap indicates that this segment contains the beginning of
247 * an nmethod. Let's walk through a simple example: If we want to find the start of
248 * an nmethod that falls into seg 2, we read the value of the segmap[2]. The value
249 * is an offset that points to the segment that contains the start of the nmethod.
250 * Another example: If we want to get the start of nm 2, and we happen to get a pointer
251 * that points to seg m+n, we first read seg[n+m], which returns '1'. So we have to
252 * do one more read of the segmap[m+n-1] to finally get the segment header.
253 */
254 void* CodeHeap::find_start(void* p) const {
255 if (!contains(p)) {
256 return NULL;
257 }
258 size_t seg_idx = segment_for(p);
259 address seg_map = (address)_segmap.low();
260 if (is_segment_unused(seg_map[seg_idx])) {
261 return NULL;
262 }
263 while (seg_map[seg_idx] > 0) {
264 seg_idx -= (int)seg_map[seg_idx];
265 }
266
267 HeapBlock* h = block_at(seg_idx);
268 if (h->free()) {
269 return NULL;
270 }
271 return h->allocated_space();
272 }
273
274
275 size_t CodeHeap::alignment_unit() const {
276 // this will be a power of two
277 return _segment_size;
278 }
279
280
281 size_t CodeHeap::alignment_offset() const {
282 // The lowest address in any allocated block will be
283 // equal to alignment_offset (mod alignment_unit).
284 return sizeof(HeapBlock) & (_segment_size - 1);
285 }
286
287 // Finds the next free heapblock. If the current one is free, that it returned
288 void* CodeHeap::next_free(HeapBlock* b) const {
289 // Since free blocks are merged, there is max. on free block
290 // between two used ones
291 if (b != NULL && b->free()) b = next_block(b);
292 assert(b == NULL || !b->free(), "must be in use or at end of heap");
293 return (b == NULL) ? NULL : b->allocated_space();
294 }
295
296 // Returns the first used HeapBlock
297 HeapBlock* CodeHeap::first_block() const {
298 if (_next_segment > 0)
299 return block_at(0);
300 return NULL;
301 }
302
303 HeapBlock* CodeHeap::block_start(void* q) const {
304 HeapBlock* b = (HeapBlock*)find_start(q);
305 if (b == NULL) return NULL;
306 return b - 1;
307 }
308
309 // Returns the next Heap block an offset into one
310 HeapBlock* CodeHeap::next_block(HeapBlock *b) const {
311 if (b == NULL) return NULL;
312 size_t i = segment_for(b) + b->length();
313 if (i < _next_segment)
314 return block_at(i);
315 return NULL;
316 }
317
318
319 // Returns current capacity
320 size_t CodeHeap::capacity() const {
321 return _memory.committed_size();
322 }
323
324 size_t CodeHeap::max_capacity() const {
325 return _memory.reserved_size();
326 }
327
328 int CodeHeap::allocated_segments() const {
329 return (int)_next_segment;
330 }
331
332 size_t CodeHeap::allocated_capacity() const {
333 // size of used heap - size on freelist
334 return segments_to_size(_next_segment - _freelist_segments);
335 }
336
337 // Returns size of the unallocated heap block
338 size_t CodeHeap::heap_unallocated_capacity() const {
339 // Total number of segments - number currently used
340 return segments_to_size(_number_of_reserved_segments - _next_segment);
341 }
342
343 // Free list management
344
345 FreeBlock* CodeHeap::following_block(FreeBlock *b) {
346 return (FreeBlock*)(((address)b) + _segment_size * b->length());
347 }
348
349 // Inserts block b after a
350 void CodeHeap::insert_after(FreeBlock* a, FreeBlock* b) {
351 assert(a != NULL && b != NULL, "must be real pointers");
352
353 // Link b into the list after a
354 b->set_link(a->link());
355 a->set_link(b);
356
357 // See if we can merge blocks
358 merge_right(b); // Try to make b bigger
359 merge_right(a); // Try to make a include b
360 }
361
362 // Try to merge this block with the following block
363 bool CodeHeap::merge_right(FreeBlock* a) {
364 assert(a->free(), "must be a free block");
365 if (following_block(a) == a->link()) {
366 assert(a->link() != NULL && a->link()->free(), "must be free too");
367 // Update block a to include the following block
368 a->set_length(a->length() + a->link()->length());
369 a->set_link(a->link()->link());
370 // Update find_start map
371 size_t beg = segment_for(a);
372 mark_segmap_as_used(beg, beg + a->length());
373 _freelist_length--;
374 return true;
375 }
376 return false;
377 }
378
379
380 void CodeHeap::add_to_freelist(HeapBlock* a) {
381 FreeBlock* b = (FreeBlock*)a;
382 _freelist_length++;
383
384 assert(b != _freelist, "cannot be removed twice");
385
386
387 // Mark as free and update free space count
388 _freelist_segments += b->length();
389 b->set_free();
390
391 // First element in list?
392 if (_freelist == NULL) {
393 _freelist = b;
394 b->set_link(NULL);
395 return;
396 }
397
398 // Since the freelist is ordered (smaller addresses -> larger addresses) and the
399 // element we want to insert into the freelist has a smaller address than the first
400 // element, we can simply add 'b' as the first element and we are done.
401 if (b < _freelist) {
402 // Insert first in list
403 b->set_link(_freelist);
404 _freelist = b;
405 merge_right(_freelist);
406 return;
407 }
408
409 // Scan for right place to put into list. List
410 // is sorted by increasing addresses
411 FreeBlock* prev = _freelist;
412 FreeBlock* cur = _freelist->link();
413 while(cur != NULL && cur < b) {
414 assert(prev < cur, "Freelist must be ordered");
415 prev = cur;
416 cur = cur->link();
417 }
418 assert((prev < b) && (cur == NULL || b < cur), "free-list must be ordered");
419 insert_after(prev, b);
420 }
421
422 /**
423 * Search freelist for an entry on the list with the best fit.
424 * @return NULL, if no one was found
425 */
426 FreeBlock* CodeHeap::search_freelist(size_t length, bool is_critical) {
427 FreeBlock* found_block = NULL;
428 FreeBlock* found_prev = NULL;
429 size_t found_length = 0;
430
431 FreeBlock* prev = NULL;
432 FreeBlock* cur = _freelist;
433 const size_t critical_boundary = (size_t)high_boundary() - CodeCacheMinimumFreeSpace;
434
435 // Search for first block that fits
436 while(cur != NULL) {
437 if (cur->length() >= length) {
438 // Non critical allocations are not allowed to use the last part of the code heap.
439 // Make sure the end of the allocation doesn't cross into the last part of the code heap.
440 if (!is_critical && (((size_t)cur + length) > critical_boundary)) {
441 // The freelist is sorted by address - if one fails, all consecutive will also fail.
442 break;
443 }
444
445 // Remember block, its previous element, and its length
446 found_block = cur;
447 found_prev = prev;
448 found_length = found_block->length();
449
450 break;
451 }
452 // Next element in list
453 prev = cur;
454 cur = cur->link();
455 }
456
457 if (found_block == NULL) {
458 // None found
459 return NULL;
460 }
461
462 // Exact (or at least good enough) fit. Remove from list.
463 // Don't leave anything on the freelist smaller than CodeCacheMinBlockLength.
464 if (found_length - length < CodeCacheMinBlockLength) {
465 _freelist_length--;
466 length = found_length;
467 if (found_prev == NULL) {
468 assert(_freelist == found_block, "sanity check");
469 _freelist = _freelist->link();
470 } else {
471 assert((found_prev->link() == found_block), "sanity check");
472 // Unmap element
473 found_prev->set_link(found_block->link());
474 }
475 } else {
476 // Truncate block and return a pointer to the following block
477 found_block->set_length(found_length - length);
478 found_block = following_block(found_block);
479 // Set used bit and length on new block
480 size_t beg = segment_for(found_block);
481 mark_segmap_as_used(beg, beg + length);
482 found_block->set_length(length);
483 }
484
485 found_block->set_used();
486 _freelist_segments -= length;
487 return found_block;
488 }
489
490 //----------------------------------------------------------------------------
491 // Non-product code
492
493 #ifndef PRODUCT
494
495 void CodeHeap::print() {
496 tty->print_cr("The Heap");
497 }
498
499 void CodeHeap::verify() {
500 if (VerifyCodeCache) {
501 size_t len = 0;
502 int count = 0;
503 for(FreeBlock* b = _freelist; b != NULL; b = b->link()) {
504 len += b->length();
505 count++;
506 // Check if we have merged all free blocks
507 assert(merge_right(b) == false, "Missed merging opportunity");
508 }
509 // Verify that freelist contains the right amount of free space
510 assert(len == _freelist_segments, "wrong freelist");
511
512 for(HeapBlock* h = first_block(); h != NULL; h = next_block(h)) {
513 if (h->free()) count--;
514 }
515 // Verify that the freelist contains the same number of blocks
516 // than free blocks found on the full list.
517 assert(count == 0, "missing free blocks");
518
519 // Verify that the number of free blocks is not out of hand.
520 static int free_block_threshold = 10000;
521 if (count > free_block_threshold) {
522 warning("CodeHeap: # of free blocks > %d", free_block_threshold);
523 // Double the warning limit
524 free_block_threshold *= 2;
525 }
526 }
527 }
528
529 #endif
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