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 _last_insert_point = NULL;
49 _freelist_segments = 0;
50 _freelist_length = 0;
51 _max_allocated_capacity = 0;
52 _blob_count = 0;
53 _nmethod_count = 0;
54 _adapter_count = 0;
55 _full_count = 0;
56 _fragmentation_count = 0;
57 }
58
59 // Dummy initialization of template array.
60 char CodeHeap::segmap_template[] = {0};
61
62 // This template array is used to (re)initialize the segmap,
63 // replacing a 1..254 loop.
64 void CodeHeap::init_segmap_template() {
65 assert(free_sentinel == 255, "Segment map logic changed!");
66 for (int i = 0; i <= free_sentinel; i++) {
67 segmap_template[i] = i;
68 }
69 }
70
71 // The segmap is marked free for that part of the heap
72 // which has not been allocated yet (beyond _next_segment).
73 // The range of segments to be marked is given by [beg..end).
74 // "Allocated" space in this context means there exists a
75 // HeapBlock or a FreeBlock describing this space.
76 // This method takes segment map indices as range boundaries
77 void CodeHeap::mark_segmap_as_free(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 // Don't do unpredictable things in PRODUCT build
81 if (beg < end) {
82 // setup _segmap pointers for faster indexing
83 address p = (address)_segmap.low() + beg;
84 address q = (address)_segmap.low() + end;
85 // initialize interval
86 memset(p, free_sentinel, q-p);
87 }
88 }
89
90 // Don't get confused here.
91 // All existing blocks, no matter if they are used() or free(),
92 // have their segmap marked as used. This allows to find the
93 // block header (HeapBlock or FreeBlock) for any pointer
94 // within the allocated range (upper limit: _next_segment).
95 // This method takes segment map indices as range boundaries.
96 // The range of segments to be marked is given by [beg..end).
97 void CodeHeap::mark_segmap_as_used(size_t beg, size_t end, bool is_FreeBlock_join) {
98 assert( beg < _number_of_committed_segments, "interval begin out of bounds");
99 assert(beg < end && end <= _number_of_committed_segments, "interval end out of bounds");
100 // Don't do unpredictable things in PRODUCT build
101 if (beg < end) {
102 // setup _segmap pointers for faster indexing
103 address p = (address)_segmap.low() + beg;
104 address q = (address)_segmap.low() + end;
105 // initialize interval
106 // If we are joining two free blocks, the segmap range for each
107 // block is consistent. To create a consistent segmap range for
108 // the blocks combined, we have three choices:
109 // 1 - Do a full init from beg to end. Not very efficient because
110 // the segmap range for the left block is potentially initialized
111 // over and over again.
112 // 2 - Carry over the last segmap element value of the left block
113 // and initialize the segmap range of the right block starting
114 // with that value. Saves initializing the left block's segmap
115 // over and over again. Very efficient if FreeBlocks mostly
116 // are appended to the right.
117 // 3 - Take full advantage of the segmap being almost correct with
118 // the two blocks combined. Lets assume the left block consists
119 // of m segments. The the segmap looks like
120 // ... (m-2) (m-1) (m) 0 1 2 3 ...
121 // By substituting the '0' by '1', we create a valid, but
122 // suboptimal, segmap range covering the two blocks combined.
123 // We introduced an extra hop for the find_block_for() iteration.
124 //
125 // When this method is called with is_FreeBlock_join == true, the
126 // segmap index beg must select the first segment of the right block.
127 // Otherwise, it has to select the first segment of the left block.
128 // Variant 3 is used for all FreeBlock joins.
129 if (is_FreeBlock_join && (beg > 0)) {
130 #ifndef PRODUCT
131 FreeBlock* pBlock = (FreeBlock*)block_at(beg);
132 assert(beg + pBlock->length() == end, "Internal error: (%d - %d) != %d", (unsigned int)end, (unsigned int)beg, (unsigned int)(pBlock->length()));
133 assert(*p == 0, "Begin index does not select a block start segment, *p = %2.2x", *p);
134 #endif
135 // If possible, extend the previous hop.
136 if (*(p-1) < (free_sentinel-1)) {
137 *p = *(p-1) + 1;
138 } else {
139 *p = 1;
140 }
141 if (_fragmentation_count++ >= fragmentation_limit) {
142 defrag_segmap(true);
143 _fragmentation_count = 0;
144 }
145 } else {
146 size_t n_bulk = free_sentinel-1; // bulk processing uses template indices [1..254].
147 // Use shortcut for blocks <= 255 segments.
148 // Special case bulk processing: [0..254].
149 if ((end - beg) <= n_bulk) {
150 memcpy(p, &segmap_template[0], end - beg);
151 } else {
152 *p++ = 0; // block header marker
153 while (p < q) {
154 if ((p+n_bulk) <= q) {
155 memcpy(p, &segmap_template[1], n_bulk);
156 p += n_bulk;
157 } else {
158 memcpy(p, &segmap_template[1], q-p);
159 p = q;
160 }
161 }
162 }
163 }
164 }
165 }
166
167 void CodeHeap::invalidate(size_t beg, size_t end, size_t hdr_size) {
168 #ifndef PRODUCT
169 // Fill the given range with some bad value.
170 // length is expected to be in segment_size units.
171 // This prevents inadvertent execution of code leftover from previous use.
172 char* p = low_boundary() + segments_to_size(beg) + hdr_size;
173 memset(p, badCodeHeapNewVal, segments_to_size(end-beg)-hdr_size);
174 #endif
175 }
176
177 void CodeHeap::clear(size_t beg, size_t end) {
178 mark_segmap_as_free(beg, end);
179 invalidate(beg, end, 0);
180 }
181
182 void CodeHeap::clear() {
183 _next_segment = 0;
184 clear(_next_segment, _number_of_committed_segments);
185 }
186
187
188 static size_t align_to_page_size(size_t size) {
189 const size_t alignment = (size_t)os::vm_page_size();
190 assert(is_power_of_2(alignment), "no kidding ???");
191 return (size + alignment - 1) & ~(alignment - 1);
192 }
193
194
195 void CodeHeap::on_code_mapping(char* base, size_t size) {
196 #ifdef LINUX
197 extern void linux_wrap_code(char* base, size_t size);
198 linux_wrap_code(base, size);
199 #endif
200 }
201
202
203 bool CodeHeap::reserve(ReservedSpace rs, size_t committed_size, size_t segment_size) {
204 assert(rs.size() >= committed_size, "reserved < committed");
205 assert(segment_size >= sizeof(FreeBlock), "segment size is too small");
206 assert(is_power_of_2(segment_size), "segment_size must be a power of 2");
207
208 _segment_size = segment_size;
209 _log2_segment_size = exact_log2(segment_size);
210
211 // Reserve and initialize space for _memory.
212 size_t page_size = os::vm_page_size();
213 if (os::can_execute_large_page_memory()) {
214 const size_t min_pages = 8;
215 page_size = MIN2(os::page_size_for_region_aligned(committed_size, min_pages),
216 os::page_size_for_region_aligned(rs.size(), min_pages));
217 }
218
219 const size_t granularity = os::vm_allocation_granularity();
220 const size_t c_size = align_up(committed_size, page_size);
221
222 os::trace_page_sizes(_name, committed_size, rs.size(), page_size,
223 rs.base(), rs.size());
224 if (!_memory.initialize(rs, c_size)) {
225 return false;
226 }
227
228 on_code_mapping(_memory.low(), _memory.committed_size());
229 _number_of_committed_segments = size_to_segments(_memory.committed_size());
230 _number_of_reserved_segments = size_to_segments(_memory.reserved_size());
231 assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking");
232 const size_t reserved_segments_alignment = MAX2((size_t)os::vm_page_size(), granularity);
233 const size_t reserved_segments_size = align_up(_number_of_reserved_segments, reserved_segments_alignment);
234 const size_t committed_segments_size = align_to_page_size(_number_of_committed_segments);
235
236 // reserve space for _segmap
237 if (!_segmap.initialize(reserved_segments_size, committed_segments_size)) {
238 return false;
239 }
240
241 MemTracker::record_virtual_memory_type((address)_segmap.low_boundary(), mtCode);
242
243 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "could not commit enough space for segment map");
244 assert(_segmap.reserved_size() >= (size_t) _number_of_reserved_segments , "could not reserve enough space for segment map");
245 assert(_segmap.reserved_size() >= _segmap.committed_size() , "just checking");
246
247 // initialize remaining instance variables, heap memory and segmap
248 clear();
249 init_segmap_template();
250 return true;
251 }
252
253
254 bool CodeHeap::expand_by(size_t size) {
255 // expand _memory space
256 size_t dm = align_to_page_size(_memory.committed_size() + size) - _memory.committed_size();
257 if (dm > 0) {
258 // Use at least the available uncommitted space if 'size' is larger
259 if (_memory.uncommitted_size() != 0 && dm > _memory.uncommitted_size()) {
260 dm = _memory.uncommitted_size();
261 }
262 char* base = _memory.low() + _memory.committed_size();
263 if (!_memory.expand_by(dm)) return false;
264 on_code_mapping(base, dm);
265 size_t i = _number_of_committed_segments;
266 _number_of_committed_segments = size_to_segments(_memory.committed_size());
267 assert(_number_of_reserved_segments == size_to_segments(_memory.reserved_size()), "number of reserved segments should not change");
268 assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking");
269 // expand _segmap space
270 size_t ds = align_to_page_size(_number_of_committed_segments) - _segmap.committed_size();
271 if ((ds > 0) && !_segmap.expand_by(ds)) {
272 return false;
273 }
274 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "just checking");
275 // initialize additional space (heap memory and segmap)
276 clear(i, _number_of_committed_segments);
277 }
278 return true;
279 }
280
281
282 void* CodeHeap::allocate(size_t instance_size) {
283 size_t number_of_segments = size_to_segments(instance_size + header_size());
284 assert(segments_to_size(number_of_segments) >= sizeof(FreeBlock), "not enough room for FreeList");
285
286 // First check if we can satisfy request from freelist
287 NOT_PRODUCT(verify());
288 HeapBlock* block = search_freelist(number_of_segments);
289 NOT_PRODUCT(verify());
290
291 if (block != NULL) {
292 assert(!block->free(), "must not be marked free");
293 guarantee((char*) block >= _memory.low_boundary() && (char*) block < _memory.high(),
294 "The newly allocated block " INTPTR_FORMAT " is not within the heap "
295 "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT,
296 p2i(block), p2i(_memory.low_boundary()), p2i(_memory.high()));
297 _max_allocated_capacity = MAX2(_max_allocated_capacity, allocated_capacity());
298 _blob_count++;
299 return block->allocated_space();
300 }
301
302 // Ensure minimum size for allocation to the heap.
303 number_of_segments = MAX2((int)CodeCacheMinBlockLength, (int)number_of_segments);
304
305 if (_next_segment + number_of_segments <= _number_of_committed_segments) {
306 mark_segmap_as_used(_next_segment, _next_segment + number_of_segments, false);
307 block = block_at(_next_segment);
308 block->initialize(number_of_segments);
309 _next_segment += number_of_segments;
310 guarantee((char*) block >= _memory.low_boundary() && (char*) block < _memory.high(),
311 "The newly allocated block " INTPTR_FORMAT " is not within the heap "
312 "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT,
313 p2i(block), p2i(_memory.low_boundary()), p2i(_memory.high()));
314 _max_allocated_capacity = MAX2(_max_allocated_capacity, allocated_capacity());
315 _blob_count++;
316 return block->allocated_space();
317 } else {
318 return NULL;
319 }
320 }
321
322 // Split the given block into two at the given segment.
323 // This is helpful when a block was allocated too large
324 // to trim off the unused space at the end (interpreter).
325 // It also helps with splitting a large free block during allocation.
326 // Usage state (used or free) must be set by caller since
327 // we don't know if the resulting blocks will be used or free.
328 // split_at is the segment number (relative to segment_for(b))
329 // where the split happens. The segment with relative
330 // number split_at is the first segment of the split-off block.
331 HeapBlock* CodeHeap::split_block(HeapBlock *b, size_t split_at) {
332 if (b == NULL) return NULL;
333 // After the split, both blocks must have a size of at least CodeCacheMinBlockLength
334 assert((split_at >= CodeCacheMinBlockLength) && (split_at + CodeCacheMinBlockLength <= b->length()),
335 "split position(%d) out of range [0..%d]", (int)split_at, (int)b->length());
336 size_t split_segment = segment_for(b) + split_at;
337 size_t b_size = b->length();
338 size_t newb_size = b_size - split_at;
339
340 HeapBlock* newb = block_at(split_segment);
341 newb->set_length(newb_size);
342 mark_segmap_as_used(segment_for(newb), segment_for(newb) + newb_size, false);
343 b->set_length(split_at);
344 return newb;
345 }
346
347 void CodeHeap::deallocate_tail(void* p, size_t used_size) {
348 assert(p == find_start(p), "illegal deallocation");
349 // Find start of HeapBlock
350 HeapBlock* b = (((HeapBlock *)p) - 1);
351 assert(b->allocated_space() == p, "sanity check");
352
353 size_t actual_number_of_segments = b->length();
354 size_t used_number_of_segments = size_to_segments(used_size + header_size());
355 size_t unused_number_of_segments = actual_number_of_segments - used_number_of_segments;
356 guarantee(used_number_of_segments <= actual_number_of_segments, "Must be!");
357
358 HeapBlock* f = split_block(b, used_number_of_segments);
359 add_to_freelist(f);
360 NOT_PRODUCT(verify());
361 }
362
363 void CodeHeap::deallocate(void* p) {
364 assert(p == find_start(p), "illegal deallocation");
365 // Find start of HeapBlock
366 HeapBlock* b = (((HeapBlock *)p) - 1);
367 assert(b->allocated_space() == p, "sanity check");
368 guarantee((char*) b >= _memory.low_boundary() && (char*) b < _memory.high(),
369 "The block to be deallocated " INTPTR_FORMAT " is not within the heap "
370 "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT,
371 p2i(b), p2i(_memory.low_boundary()), p2i(_memory.high()));
372 add_to_freelist(b);
373 NOT_PRODUCT(verify());
374 }
375
376 /**
377 * The segment map is used to quickly find the the start (header) of a
378 * code block (e.g. nmethod) when only a pointer to a location inside the
379 * code block is known. This works as follows:
380 * - The storage reserved for the code heap is divided into 'segments'.
381 * - The size of a segment is determined by -XX:CodeCacheSegmentSize=<#bytes>.
382 * - The size must be a power of two to allow the use of shift operations
383 * to quickly convert between segment index and segment address.
384 * - Segment start addresses should be aligned to be multiples of CodeCacheSegmentSize.
385 * - It seems beneficial for CodeCacheSegmentSize to be equal to os::page_size().
386 * - Allocation in the code cache can only happen at segment start addresses.
387 * - Allocation in the code cache is in units of CodeCacheSegmentSize.
388 * - A pointer in the code cache can be mapped to a segment by calling
389 * segment_for(addr).
390 * - The segment map is a byte array where array element [i] is related
391 * to the i-th segment in the code heap.
392 * - Each time memory is allocated/deallocated from the code cache,
393 * the segment map is updated accordingly.
394 * Note: deallocation does not cause the memory to become "free", as
395 * indicated by the segment map state "free_sentinel". Deallocation
396 * just changes the block state from "used" to "free".
397 * - Elements of the segment map (byte) array are interpreted
398 * as unsigned integer.
399 * - Element values normally identify an offset backwards (in segment
400 * size units) from the associated segment towards the start of
401 * the block.
402 * - Some values have a special meaning:
403 * 0 - This segment is the start of a block (HeapBlock or FreeBlock).
404 * 255 - The free_sentinel value. This is a free segment, i.e. it is
405 * not yet allocated and thus does not belong to any block.
406 * - The value of the current element has to be subtracted from the
407 * current index to get closer to the start.
408 * - If the value of the then current element is zero, the block start
409 * segment is found and iteration stops. Otherwise, start over with the
410 * previous step.
411 *
412 * The following example illustrates a possible state of code cache
413 * and the segment map: (seg -> segment, nm ->nmethod)
414 *
415 * code cache segmap
416 * ----------- ---------
417 * seg 1 | nm 1 | -> | 0 |
418 * seg 2 | nm 1 | -> | 1 |
419 * ... | nm 1 | -> | .. |
420 * seg m-1 | nm 1 | -> | m-1 |
421 * seg m | nm 2 | -> | 0 |
422 * seg m+1 | nm 2 | -> | 1 |
423 * ... | nm 2 | -> | 2 |
424 * ... | nm 2 | -> | .. |
425 * ... | nm 2 | -> | 0xFE | (free_sentinel-1)
426 * ... | nm 2 | -> | 1 |
427 * seg m+n | nm 2 | -> | 2 |
428 * ... | nm 2 | -> | |
429 *
430 * How to read:
431 * A value of '0' in the segmap indicates that this segment contains the
432 * beginning of a CodeHeap block. Let's walk through a simple example:
433 *
434 * We want to find the start of the block that contains nm 1, and we are
435 * given a pointer that points into segment m-2. We then read the value
436 * of segmap[m-2]. The value is an offset that points to the segment
437 * which contains the start of the block.
438 *
439 * Another example: We want to locate the start of nm 2, and we happen to
440 * get a pointer that points into seg m+n. We first read seg[n+m], which
441 * returns '2'. So we have to update our segment map index (ix -= segmap[n+m])
442 * and start over.
443 */
444
445 // Find block which contains the passed pointer,
446 // regardless of the block being used or free.
447 // NULL is returned if anything invalid is detected.
448 void* CodeHeap::find_block_for(void* p) const {
449 // Check the pointer to be in committed range.
450 if (!contains(p)) {
451 return NULL;
452 }
453
454 address seg_map = (address)_segmap.low();
455 size_t seg_idx = segment_for(p);
456
457 // This may happen in special cases. Just ignore.
458 // Example: PPC ICache stub generation.
459 if (is_segment_unused(seg_map[seg_idx])) {
460 return NULL;
461 }
462
463 // Iterate the segment map chain to find the start of the block.
464 while (seg_map[seg_idx] > 0) {
465 // Don't check each segment index to refer to a used segment.
466 // This method is called extremely often. Therefore, any checking
467 // has a significant impact on performance. Rely on CodeHeap::verify()
468 // to do the job on request.
469 seg_idx -= (int)seg_map[seg_idx];
470 }
471
472 return address_for(seg_idx);
473 }
474
475 // Find block which contains the passed pointer.
476 // The block must be used, i.e. must not be a FreeBlock.
477 // Return a pointer that points past the block header.
478 void* CodeHeap::find_start(void* p) const {
479 HeapBlock* h = (HeapBlock*)find_block_for(p);
480 return ((h == NULL) || h->free()) ? NULL : h->allocated_space();
481 }
482
483 // Find block which contains the passed pointer.
484 // Same as find_start(p), but with additional safety net.
485 CodeBlob* CodeHeap::find_blob_unsafe(void* start) const {
486 CodeBlob* result = (CodeBlob*)CodeHeap::find_start(start);
487 return (result != NULL && result->blob_contains((address)start)) ? result : NULL;
488 }
489
490 size_t CodeHeap::alignment_unit() const {
491 // this will be a power of two
492 return _segment_size;
493 }
494
495
496 size_t CodeHeap::alignment_offset() const {
497 // The lowest address in any allocated block will be
498 // equal to alignment_offset (mod alignment_unit).
499 return sizeof(HeapBlock) & (_segment_size - 1);
500 }
501
502 // Returns the current block if available and used.
503 // If not, it returns the subsequent block (if available), NULL otherwise.
504 // Free blocks are merged, therefore there is at most one free block
505 // between two used ones. As a result, the subsequent block (if available) is
506 // guaranteed to be used.
507 // The returned pointer points past the block header.
508 void* CodeHeap::next_used(HeapBlock* b) const {
509 if (b != NULL && b->free()) b = next_block(b);
510 assert(b == NULL || !b->free(), "must be in use or at end of heap");
511 return (b == NULL) ? NULL : b->allocated_space();
512 }
513
514 // Returns the first used HeapBlock
515 // The returned pointer points to the block header.
516 HeapBlock* CodeHeap::first_block() const {
517 if (_next_segment > 0)
518 return block_at(0);
519 return NULL;
520 }
521
522 // The returned pointer points to the block header.
523 HeapBlock* CodeHeap::block_start(void* q) const {
524 HeapBlock* b = (HeapBlock*)find_start(q);
525 if (b == NULL) return NULL;
526 return b - 1;
527 }
528
529 // Returns the next Heap block.
530 // The returned pointer points to the block header.
531 HeapBlock* CodeHeap::next_block(HeapBlock *b) const {
532 if (b == NULL) return NULL;
533 size_t i = segment_for(b) + b->length();
534 if (i < _next_segment)
535 return block_at(i);
536 return NULL;
537 }
538
539
540 // Returns current capacity
541 size_t CodeHeap::capacity() const {
542 return _memory.committed_size();
543 }
544
545 size_t CodeHeap::max_capacity() const {
546 return _memory.reserved_size();
547 }
548
549 int CodeHeap::allocated_segments() const {
550 return (int)_next_segment;
551 }
552
553 size_t CodeHeap::allocated_capacity() const {
554 // size of used heap - size on freelist
555 return segments_to_size(_next_segment - _freelist_segments);
556 }
557
558 // Returns size of the unallocated heap block
559 size_t CodeHeap::heap_unallocated_capacity() const {
560 // Total number of segments - number currently used
561 return segments_to_size(_number_of_reserved_segments - _next_segment);
562 }
563
564 // Free list management
565
566 FreeBlock* CodeHeap::following_block(FreeBlock *b) {
567 return (FreeBlock*)(((address)b) + _segment_size * b->length());
568 }
569
570 // Inserts block b after a
571 void CodeHeap::insert_after(FreeBlock* a, FreeBlock* b) {
572 assert(a != NULL && b != NULL, "must be real pointers");
573
574 // Link b into the list after a
575 b->set_link(a->link());
576 a->set_link(b);
577
578 // See if we can merge blocks
579 merge_right(b); // Try to make b bigger
580 merge_right(a); // Try to make a include b
581 }
582
583 // Try to merge this block with the following block
584 bool CodeHeap::merge_right(FreeBlock* a) {
585 assert(a->free(), "must be a free block");
586 if (following_block(a) == a->link()) {
587 assert(a->link() != NULL && a->link()->free(), "must be free too");
588
589 // Remember linked (following) block. invalidate should only zap header of this block.
590 size_t follower = segment_for(a->link());
591 // Merge block a to include the following block.
592 a->set_length(a->length() + a->link()->length());
593 a->set_link(a->link()->link());
594
595 // Update the segment map and invalidate block contents.
596 mark_segmap_as_used(follower, segment_for(a) + a->length(), true);
597 // Block contents has already been invalidated by add_to_freelist.
598 // What's left is the header of the following block which now is
599 // in the middle of the merged block. Just zap one segment.
600 invalidate(follower, follower + 1, 0);
601
602 _freelist_length--;
603 return true;
604 }
605 return false;
606 }
607
608
609 void CodeHeap::add_to_freelist(HeapBlock* a) {
610 FreeBlock* b = (FreeBlock*)a;
611 size_t bseg = segment_for(b);
612 _freelist_length++;
613
614 _blob_count--;
615 assert(_blob_count >= 0, "sanity");
616
617 assert(b != _freelist, "cannot be removed twice");
618
619 // Mark as free and update free space count
620 _freelist_segments += b->length();
621 b->set_free();
622 invalidate(bseg, bseg + b->length(), sizeof(FreeBlock));
623
624 // First element in list?
625 if (_freelist == NULL) {
626 b->set_link(NULL);
627 _freelist = b;
628 return;
629 }
630
631 // Since the freelist is ordered (smaller addresses -> larger addresses) and the
632 // element we want to insert into the freelist has a smaller address than the first
633 // element, we can simply add 'b' as the first element and we are done.
634 if (b < _freelist) {
635 // Insert first in list
636 b->set_link(_freelist);
637 _freelist = b;
638 merge_right(_freelist);
639 return;
640 }
641
642 // Scan for right place to put into list.
643 // List is sorted by increasing addresses.
644 FreeBlock* prev = _freelist;
645 FreeBlock* cur = _freelist->link();
646 if ((_freelist_length > freelist_limit) && (_last_insert_point != NULL)) {
647 _last_insert_point = (FreeBlock*)find_block_for(_last_insert_point);
648 if ((_last_insert_point != NULL) && _last_insert_point->free() && (_last_insert_point < b)) {
649 prev = _last_insert_point;
650 cur = prev->link();
651 }
652 }
653 while(cur != NULL && cur < b) {
654 assert(prev < cur, "Freelist must be ordered");
655 prev = cur;
656 cur = cur->link();
657 }
658 assert((prev < b) && (cur == NULL || b < cur), "free-list must be ordered");
659 insert_after(prev, b);
660 _last_insert_point = prev;
661 }
662
663 /**
664 * Search freelist for an entry on the list with the best fit.
665 * @return NULL, if no one was found
666 */
667 HeapBlock* CodeHeap::search_freelist(size_t length) {
668 FreeBlock* found_block = NULL;
669 FreeBlock* found_prev = NULL;
670 size_t found_length = _next_segment; // max it out to begin with
671
672 HeapBlock* res = NULL;
673 FreeBlock* prev = NULL;
674 FreeBlock* cur = _freelist;
675
676 length = length < CodeCacheMinBlockLength ? CodeCacheMinBlockLength : length;
677
678 // Search for best-fitting block
679 while(cur != NULL) {
680 size_t cur_length = cur->length();
681 if (cur_length == length) {
682 // We have a perfect fit
683 found_block = cur;
684 found_prev = prev;
685 found_length = cur_length;
686 break;
687 } else if ((cur_length > length) && (cur_length < found_length)) {
688 // This is a new, closer fit. Remember block, its previous element, and its length
689 found_block = cur;
690 found_prev = prev;
691 found_length = cur_length;
692 }
693 // Next element in list
694 prev = cur;
695 cur = cur->link();
696 }
697
698 if (found_block == NULL) {
699 // None found
700 return NULL;
701 }
702
703 // Exact (or at least good enough) fit. Remove from list.
704 // Don't leave anything on the freelist smaller than CodeCacheMinBlockLength.
705 if (found_length - length < CodeCacheMinBlockLength) {
706 _freelist_length--;
707 length = found_length;
708 if (found_prev == NULL) {
709 assert(_freelist == found_block, "sanity check");
710 _freelist = _freelist->link();
711 } else {
712 assert((found_prev->link() == found_block), "sanity check");
713 // Unmap element
714 found_prev->set_link(found_block->link());
715 }
716 res = (HeapBlock*)found_block;
717 // sizeof(HeapBlock) < sizeof(FreeBlock).
718 // Invalidate the additional space that FreeBlock occupies.
719 // The rest of the block should already be invalidated.
720 // This is necessary due to a dubious assert in nmethod.cpp(PcDescCache::reset_to()).
721 // Can't use invalidate() here because it works on segment_size units (too coarse).
722 DEBUG_ONLY(memset((void*)res->allocated_space(), badCodeHeapNewVal, sizeof(FreeBlock) - sizeof(HeapBlock)));
723 } else {
724 // Truncate the free block and return the truncated part
725 // as new HeapBlock. The remaining free block does not
726 // need to be updated, except for it's length. Truncating
727 // the segment map does not invalidate the leading part.
728 res = split_block(found_block, found_length - length);
729 }
730
731 res->set_used();
732 _freelist_segments -= length;
733 return res;
734 }
735
736 int CodeHeap::defrag_segmap(bool do_defrag) {
737 int extra_hops_used = 0;
738 int extra_hops_free = 0;
739 int blocks_used = 0;
740 int blocks_free = 0;
741 for(HeapBlock* h = first_block(); h != NULL; h = next_block(h)) {
742 size_t beg = segment_for(h);
743 size_t end = segment_for(h) + h->length();
744 int extra_hops = segmap_hops(beg, end);
745 if (h->free()) {
746 extra_hops_free += extra_hops;
747 blocks_free++;
748 } else {
749 extra_hops_used += extra_hops;
750 blocks_used++;
751 }
752 if (do_defrag && (extra_hops > 0)) {
753 mark_segmap_as_used(beg, end, false);
754 }
755 }
756 return extra_hops_used + extra_hops_free;
757 }
758
759 // Count the hops required to get from the last segment of a
760 // heap block to the block header segment. For the optimal case,
761 // #hops = ((#segments-1)+(free_sentinel-2))/(free_sentinel-1)
762 // The range of segments to be checked is given by [beg..end).
763 // Return the number of extra hops required. There may be extra hops
764 // due to the is_FreeBlock_join optimization in mark_segmap_as_used().
765 int CodeHeap::segmap_hops(size_t beg, size_t end) {
766 if (beg < end) {
767 // setup _segmap pointers for faster indexing
768 address p = (address)_segmap.low() + beg;
769 int hops_expected = (int)(((end-beg-1)+(free_sentinel-2))/(free_sentinel-1));
770 int nhops = 0;
771 size_t ix = end-beg-1;
772 while (p[ix] > 0) {
773 ix -= p[ix];
774 nhops++;
775 }
776 return (nhops > hops_expected) ? nhops - hops_expected : 0;
777 }
778 return 0;
779 }
780
781 //----------------------------------------------------------------------------
782 // Non-product code
783
784 #ifndef PRODUCT
785
786 void CodeHeap::print() {
787 tty->print_cr("The Heap");
788 }
789
790 void CodeHeap::verify() {
791 if (VerifyCodeCache) {
792 size_t len = 0;
793 int count = 0;
794 for(FreeBlock* b = _freelist; b != NULL; b = b->link()) {
795 len += b->length();
796 count++;
797 // Check if we have merged all free blocks
798 assert(merge_right(b) == false, "Missed merging opportunity");
799 }
800 // Verify that freelist contains the right amount of free space
801 assert(len == _freelist_segments, "wrong freelist");
802
803 for(HeapBlock* h = first_block(); h != NULL; h = next_block(h)) {
804 if (h->free()) count--;
805 }
806 // Verify that the freelist contains the same number of blocks
807 // than free blocks found on the full list.
808 assert(count == 0, "missing free blocks");
809
810 //---< all free block memory must have been invalidated >---
811 for(FreeBlock* b = _freelist; b != NULL; b = b->link()) {
812 for (char* c = (char*)b + sizeof(FreeBlock); c < (char*)b + segments_to_size(b->length()); c++) {
813 assert(*c == (char)badCodeHeapNewVal, "FreeBlock@" PTR_FORMAT "(" PTR_FORMAT ") not invalidated @byte %d", p2i(b), b->length(), (int)(c - (char*)b));
814 }
815 }
816
817 address seg_map = (address)_segmap.low();
818 size_t nseg = 0;
819 int extra_hops = 0;
820 count = 0;
821 for(HeapBlock* b = first_block(); b != NULL; b = next_block(b)) {
822 size_t seg1 = segment_for(b);
823 size_t segn = seg1 + b->length();
824 extra_hops += segmap_hops(seg1, segn);
825 count++;
826 for (size_t i = seg1; i < segn; i++) {
827 nseg++;
828 //---< Verify segment map marking >---
829 // All allocated segments, no matter if in a free or used block,
830 // must be marked "in use".
831 assert(!is_segment_unused(seg_map[i]), "CodeHeap: unused segment. seg_map[%d]([%d..%d]) = %d, %s block", (int)i, (int)seg1, (int)segn, seg_map[i], b->free()? "free":"used");
832 assert((unsigned char)seg_map[i] < free_sentinel, "CodeHeap: seg_map[%d]([%d..%d]) = %d (out of range)", (int)i, (int)seg1, (int)segn, seg_map[i]);
833 }
834 }
835 assert(nseg == _next_segment, "CodeHeap: segment count mismatch. found %d, expected %d.", (int)nseg, (int)_next_segment);
836 assert((count == 0) || (extra_hops < (16 + 2*count)), "CodeHeap: many extra hops due to optimization. blocks: %d, extra hops: %d.", count, extra_hops);
837
838 // Verify that the number of free blocks is not out of hand.
839 static int free_block_threshold = 10000;
840 if (count > free_block_threshold) {
841 warning("CodeHeap: # of free blocks > %d", free_block_threshold);
842 // Double the warning limit
843 free_block_threshold *= 2;
844 }
845 }
846 }
847
848 #endif