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 #include "utilities/powerOfTwo.hpp"
32
33 size_t CodeHeap::header_size() {
34 return sizeof(HeapBlock);
35 }
36
37
38 // Implementation of Heap
39
40 CodeHeap::CodeHeap(const char* name, const int code_blob_type)
41 : _code_blob_type(code_blob_type) {
42 _name = name;
43 _number_of_committed_segments = 0;
44 _number_of_reserved_segments = 0;
45 _segment_size = 0;
46 _log2_segment_size = 0;
47 _next_segment = 0;
48 _freelist = NULL;
49 _last_insert_point = NULL;
50 _freelist_segments = 0;
51 _freelist_length = 0;
52 _max_allocated_capacity = 0;
53 _blob_count = 0;
54 _nmethod_count = 0;
55 _adapter_count = 0;
56 _full_count = 0;
57 _fragmentation_count = 0;
58 }
59
60 // Dummy initialization of template array.
61 char CodeHeap::segmap_template[] = {0};
62
63 // This template array is used to (re)initialize the segmap,
64 // replacing a 1..254 loop.
65 void CodeHeap::init_segmap_template() {
66 assert(free_sentinel == 255, "Segment map logic changed!");
67 for (int i = 0; i <= free_sentinel; i++) {
68 segmap_template[i] = i;
69 }
70 }
71
72 // The segmap is marked free for that part of the heap
73 // which has not been allocated yet (beyond _next_segment).
74 // The range of segments to be marked is given by [beg..end).
75 // "Allocated" space in this context means there exists a
76 // HeapBlock or a FreeBlock describing this space.
77 // This method takes segment map indices as range boundaries
78 void CodeHeap::mark_segmap_as_free(size_t beg, size_t end) {
79 assert( beg < _number_of_committed_segments, "interval begin out of bounds");
80 assert(beg < end && end <= _number_of_committed_segments, "interval end out of bounds");
81 // Don't do unpredictable things in PRODUCT build
82 if (beg < end) {
83 // setup _segmap pointers for faster indexing
84 address p = (address)_segmap.low() + beg;
85 address q = (address)_segmap.low() + end;
86 // initialize interval
87 memset(p, free_sentinel, q-p);
88 }
89 }
90
91 // Don't get confused here.
92 // All existing blocks, no matter if they are used() or free(),
93 // have their segmap marked as used. This allows to find the
94 // block header (HeapBlock or FreeBlock) for any pointer
95 // within the allocated range (upper limit: _next_segment).
96 // This method takes segment map indices as range boundaries.
97 // The range of segments to be marked is given by [beg..end).
98 void CodeHeap::mark_segmap_as_used(size_t beg, size_t end, bool is_FreeBlock_join) {
99 assert( beg < _number_of_committed_segments, "interval begin out of bounds");
100 assert(beg < end && end <= _number_of_committed_segments, "interval end out of bounds");
101 // Don't do unpredictable things in PRODUCT build
102 if (beg < end) {
103 // setup _segmap pointers for faster indexing
104 address p = (address)_segmap.low() + beg;
105 address q = (address)_segmap.low() + end;
106 // initialize interval
107 // If we are joining two free blocks, the segmap range for each
108 // block is consistent. To create a consistent segmap range for
109 // the blocks combined, we have three choices:
110 // 1 - Do a full init from beg to end. Not very efficient because
111 // the segmap range for the left block is potentially initialized
112 // over and over again.
113 // 2 - Carry over the last segmap element value of the left block
114 // and initialize the segmap range of the right block starting
115 // with that value. Saves initializing the left block's segmap
116 // over and over again. Very efficient if FreeBlocks mostly
117 // are appended to the right.
118 // 3 - Take full advantage of the segmap being almost correct with
119 // the two blocks combined. Lets assume the left block consists
120 // of m segments. The the segmap looks like
121 // ... (m-2) (m-1) (m) 0 1 2 3 ...
122 // By substituting the '0' by '1', we create a valid, but
123 // suboptimal, segmap range covering the two blocks combined.
124 // We introduced an extra hop for the find_block_for() iteration.
125 //
126 // When this method is called with is_FreeBlock_join == true, the
127 // segmap index beg must select the first segment of the right block.
128 // Otherwise, it has to select the first segment of the left block.
129 // Variant 3 is used for all FreeBlock joins.
130 if (is_FreeBlock_join && (beg > 0)) {
131 #ifndef PRODUCT
132 FreeBlock* pBlock = (FreeBlock*)block_at(beg);
133 assert(beg + pBlock->length() == end, "Internal error: (%d - %d) != %d", (unsigned int)end, (unsigned int)beg, (unsigned int)(pBlock->length()));
134 assert(*p == 0, "Begin index does not select a block start segment, *p = %2.2x", *p);
135 #endif
136 // If possible, extend the previous hop.
137 if (*(p-1) < (free_sentinel-1)) {
138 *p = *(p-1) + 1;
139 } else {
140 *p = 1;
141 }
142 if (_fragmentation_count++ >= fragmentation_limit) {
143 defrag_segmap(true);
144 _fragmentation_count = 0;
145 }
146 } else {
147 size_t n_bulk = free_sentinel-1; // bulk processing uses template indices [1..254].
148 // Use shortcut for blocks <= 255 segments.
149 // Special case bulk processing: [0..254].
150 if ((end - beg) <= n_bulk) {
151 memcpy(p, &segmap_template[0], end - beg);
152 } else {
153 *p++ = 0; // block header marker
154 while (p < q) {
155 if ((p+n_bulk) <= q) {
156 memcpy(p, &segmap_template[1], n_bulk);
157 p += n_bulk;
158 } else {
159 memcpy(p, &segmap_template[1], q-p);
160 p = q;
161 }
162 }
163 }
164 }
165 }
166 }
167
168 void CodeHeap::invalidate(size_t beg, size_t end, size_t hdr_size) {
169 #ifndef PRODUCT
170 // Fill the given range with some bad value.
171 // length is expected to be in segment_size units.
172 // This prevents inadvertent execution of code leftover from previous use.
173 char* p = low_boundary() + segments_to_size(beg) + hdr_size;
174 memset(p, badCodeHeapNewVal, segments_to_size(end-beg)-hdr_size);
175 #endif
176 }
177
178 void CodeHeap::clear(size_t beg, size_t end) {
179 mark_segmap_as_free(beg, end);
180 invalidate(beg, end, 0);
181 }
182
183 void CodeHeap::clear() {
184 _next_segment = 0;
185 clear(_next_segment, _number_of_committed_segments);
186 }
187
188
189 static size_t align_to_page_size(size_t size) {
190 const size_t alignment = (size_t)os::vm_page_size();
191 assert(is_power_of_2(alignment), "no kidding ???");
192 return (size + alignment - 1) & ~(alignment - 1);
193 }
194
195
196 void CodeHeap::on_code_mapping(char* base, size_t size) {
197 #ifdef LINUX
198 extern void linux_wrap_code(char* base, size_t size);
199 linux_wrap_code(base, size);
200 #endif
201 }
202
203
204 bool CodeHeap::reserve(ReservedSpace rs, size_t committed_size, size_t segment_size) {
205 assert(rs.size() >= committed_size, "reserved < committed");
206 assert(segment_size >= sizeof(FreeBlock), "segment size is too small");
207 assert(is_power_of_2(segment_size), "segment_size must be a power of 2");
208 assert_locked_or_safepoint(CodeCache_lock);
209
210 _segment_size = segment_size;
211 _log2_segment_size = exact_log2(segment_size);
212
213 // Reserve and initialize space for _memory.
214 size_t page_size = os::vm_page_size();
215 if (os::can_execute_large_page_memory()) {
216 const size_t min_pages = 8;
217 page_size = MIN2(os::page_size_for_region_aligned(committed_size, min_pages),
218 os::page_size_for_region_aligned(rs.size(), min_pages));
219 }
220
221 const size_t granularity = os::vm_allocation_granularity();
222 const size_t c_size = align_up(committed_size, page_size);
223
224 os::trace_page_sizes(_name, committed_size, rs.size(), page_size,
225 rs.base(), rs.size());
226 if (!_memory.initialize(rs, c_size)) {
227 return false;
228 }
229
230 on_code_mapping(_memory.low(), _memory.committed_size());
231 _number_of_committed_segments = size_to_segments(_memory.committed_size());
232 _number_of_reserved_segments = size_to_segments(_memory.reserved_size());
233 assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking");
234 const size_t reserved_segments_alignment = MAX2((size_t)os::vm_page_size(), granularity);
235 const size_t reserved_segments_size = align_up(_number_of_reserved_segments, reserved_segments_alignment);
236 const size_t committed_segments_size = align_to_page_size(_number_of_committed_segments);
237
238 // reserve space for _segmap
239 if (!_segmap.initialize(reserved_segments_size, committed_segments_size)) {
240 return false;
241 }
242
243 MemTracker::record_virtual_memory_type((address)_segmap.low_boundary(), mtCode);
244
245 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "could not commit enough space for segment map");
246 assert(_segmap.reserved_size() >= (size_t) _number_of_reserved_segments , "could not reserve enough space for segment map");
247 assert(_segmap.reserved_size() >= _segmap.committed_size() , "just checking");
248
249 // initialize remaining instance variables, heap memory and segmap
250 clear();
251 init_segmap_template();
252 return true;
253 }
254
255
256 bool CodeHeap::expand_by(size_t size) {
257 assert_locked_or_safepoint(CodeCache_lock);
258
259 // expand _memory space
260 size_t dm = align_to_page_size(_memory.committed_size() + size) - _memory.committed_size();
261 if (dm > 0) {
262 // Use at least the available uncommitted space if 'size' is larger
263 if (_memory.uncommitted_size() != 0 && dm > _memory.uncommitted_size()) {
264 dm = _memory.uncommitted_size();
265 }
266 char* base = _memory.low() + _memory.committed_size();
267 if (!_memory.expand_by(dm)) return false;
268 on_code_mapping(base, dm);
269 size_t i = _number_of_committed_segments;
270 _number_of_committed_segments = size_to_segments(_memory.committed_size());
271 assert(_number_of_reserved_segments == size_to_segments(_memory.reserved_size()), "number of reserved segments should not change");
272 assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking");
273 // expand _segmap space
274 size_t ds = align_to_page_size(_number_of_committed_segments) - _segmap.committed_size();
275 if ((ds > 0) && !_segmap.expand_by(ds)) {
276 return false;
277 }
278 assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "just checking");
279 // initialize additional space (heap memory and segmap)
280 clear(i, _number_of_committed_segments);
281 }
282 return true;
283 }
284
285
286 void* CodeHeap::allocate(size_t instance_size) {
287 size_t number_of_segments = size_to_segments(instance_size + header_size());
288 assert(segments_to_size(number_of_segments) >= sizeof(FreeBlock), "not enough room for FreeList");
289 assert_locked_or_safepoint(CodeCache_lock);
290
291 // First check if we can satisfy request from freelist
292 NOT_PRODUCT(verify());
293 HeapBlock* block = search_freelist(number_of_segments);
294 NOT_PRODUCT(verify());
295
296 if (block != NULL) {
297 assert(!block->free(), "must not be marked free");
298 guarantee((char*) block >= _memory.low_boundary() && (char*) block < _memory.high(),
299 "The newly allocated block " INTPTR_FORMAT " is not within the heap "
300 "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT,
301 p2i(block), p2i(_memory.low_boundary()), p2i(_memory.high()));
302 _max_allocated_capacity = MAX2(_max_allocated_capacity, allocated_capacity());
303 _blob_count++;
304 return block->allocated_space();
305 }
306
307 // Ensure minimum size for allocation to the heap.
308 number_of_segments = MAX2((int)CodeCacheMinBlockLength, (int)number_of_segments);
309
310 if (_next_segment + number_of_segments <= _number_of_committed_segments) {
311 mark_segmap_as_used(_next_segment, _next_segment + number_of_segments, false);
312 block = block_at(_next_segment);
313 block->initialize(number_of_segments);
314 _next_segment += number_of_segments;
315 guarantee((char*) block >= _memory.low_boundary() && (char*) block < _memory.high(),
316 "The newly allocated block " INTPTR_FORMAT " is not within the heap "
317 "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT,
318 p2i(block), p2i(_memory.low_boundary()), p2i(_memory.high()));
319 _max_allocated_capacity = MAX2(_max_allocated_capacity, allocated_capacity());
320 _blob_count++;
321 return block->allocated_space();
322 } else {
323 return NULL;
324 }
325 }
326
327 // Split the given block into two at the given segment.
328 // This is helpful when a block was allocated too large
329 // to trim off the unused space at the end (interpreter).
330 // It also helps with splitting a large free block during allocation.
331 // Usage state (used or free) must be set by caller since
332 // we don't know if the resulting blocks will be used or free.
333 // split_at is the segment number (relative to segment_for(b))
334 // where the split happens. The segment with relative
335 // number split_at is the first segment of the split-off block.
336 HeapBlock* CodeHeap::split_block(HeapBlock *b, size_t split_at) {
337 if (b == NULL) return NULL;
338 // After the split, both blocks must have a size of at least CodeCacheMinBlockLength
339 assert((split_at >= CodeCacheMinBlockLength) && (split_at + CodeCacheMinBlockLength <= b->length()),
340 "split position(%d) out of range [0..%d]", (int)split_at, (int)b->length());
341 size_t split_segment = segment_for(b) + split_at;
342 size_t b_size = b->length();
343 size_t newb_size = b_size - split_at;
344
345 HeapBlock* newb = block_at(split_segment);
346 newb->set_length(newb_size);
347 mark_segmap_as_used(segment_for(newb), segment_for(newb) + newb_size, false);
348 b->set_length(split_at);
349 return newb;
350 }
351
352 void CodeHeap::deallocate_tail(void* p, size_t used_size) {
353 assert(p == find_start(p), "illegal deallocation");
354 assert_locked_or_safepoint(CodeCache_lock);
355
356 // Find start of HeapBlock
357 HeapBlock* b = (((HeapBlock *)p) - 1);
358 assert(b->allocated_space() == p, "sanity check");
359
360 size_t actual_number_of_segments = b->length();
361 size_t used_number_of_segments = size_to_segments(used_size + header_size());
362 size_t unused_number_of_segments = actual_number_of_segments - used_number_of_segments;
363 guarantee(used_number_of_segments <= actual_number_of_segments, "Must be!");
364
365 HeapBlock* f = split_block(b, used_number_of_segments);
366 add_to_freelist(f);
367 NOT_PRODUCT(verify());
368 }
369
370 void CodeHeap::deallocate(void* p) {
371 assert(p == find_start(p), "illegal deallocation");
372 assert_locked_or_safepoint(CodeCache_lock);
373
374 // Find start of HeapBlock
375 HeapBlock* b = (((HeapBlock *)p) - 1);
376 assert(b->allocated_space() == p, "sanity check");
377 guarantee((char*) b >= _memory.low_boundary() && (char*) b < _memory.high(),
378 "The block to be deallocated " INTPTR_FORMAT " is not within the heap "
379 "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT,
380 p2i(b), p2i(_memory.low_boundary()), p2i(_memory.high()));
381 add_to_freelist(b);
382 NOT_PRODUCT(verify());
383 }
384
385 /**
386 * The segment map is used to quickly find the the start (header) of a
387 * code block (e.g. nmethod) when only a pointer to a location inside the
388 * code block is known. This works as follows:
389 * - The storage reserved for the code heap is divided into 'segments'.
390 * - The size of a segment is determined by -XX:CodeCacheSegmentSize=<#bytes>.
391 * - The size must be a power of two to allow the use of shift operations
392 * to quickly convert between segment index and segment address.
393 * - Segment start addresses should be aligned to be multiples of CodeCacheSegmentSize.
394 * - It seems beneficial for CodeCacheSegmentSize to be equal to os::page_size().
395 * - Allocation in the code cache can only happen at segment start addresses.
396 * - Allocation in the code cache is in units of CodeCacheSegmentSize.
397 * - A pointer in the code cache can be mapped to a segment by calling
398 * segment_for(addr).
399 * - The segment map is a byte array where array element [i] is related
400 * to the i-th segment in the code heap.
401 * - Each time memory is allocated/deallocated from the code cache,
402 * the segment map is updated accordingly.
403 * Note: deallocation does not cause the memory to become "free", as
404 * indicated by the segment map state "free_sentinel". Deallocation
405 * just changes the block state from "used" to "free".
406 * - Elements of the segment map (byte) array are interpreted
407 * as unsigned integer.
408 * - Element values normally identify an offset backwards (in segment
409 * size units) from the associated segment towards the start of
410 * the block.
411 * - Some values have a special meaning:
412 * 0 - This segment is the start of a block (HeapBlock or FreeBlock).
413 * 255 - The free_sentinel value. This is a free segment, i.e. it is
414 * not yet allocated and thus does not belong to any block.
415 * - The value of the current element has to be subtracted from the
416 * current index to get closer to the start.
417 * - If the value of the then current element is zero, the block start
418 * segment is found and iteration stops. Otherwise, start over with the
419 * previous step.
420 *
421 * The following example illustrates a possible state of code cache
422 * and the segment map: (seg -> segment, nm ->nmethod)
423 *
424 * code cache segmap
425 * ----------- ---------
426 * seg 1 | nm 1 | -> | 0 |
427 * seg 2 | nm 1 | -> | 1 |
428 * ... | nm 1 | -> | .. |
429 * seg m-1 | nm 1 | -> | m-1 |
430 * seg m | nm 2 | -> | 0 |
431 * seg m+1 | nm 2 | -> | 1 |
432 * ... | nm 2 | -> | 2 |
433 * ... | nm 2 | -> | .. |
434 * ... | nm 2 | -> | 0xFE | (free_sentinel-1)
435 * ... | nm 2 | -> | 1 |
436 * seg m+n | nm 2 | -> | 2 |
437 * ... | nm 2 | -> | |
438 *
439 * How to read:
440 * A value of '0' in the segmap indicates that this segment contains the
441 * beginning of a CodeHeap block. Let's walk through a simple example:
442 *
443 * We want to find the start of the block that contains nm 1, and we are
444 * given a pointer that points into segment m-2. We then read the value
445 * of segmap[m-2]. The value is an offset that points to the segment
446 * which contains the start of the block.
447 *
448 * Another example: We want to locate the start of nm 2, and we happen to
449 * get a pointer that points into seg m+n. We first read seg[n+m], which
450 * returns '2'. So we have to update our segment map index (ix -= segmap[n+m])
451 * and start over.
452 */
453
454 // Find block which contains the passed pointer,
455 // regardless of the block being used or free.
456 // NULL is returned if anything invalid is detected.
457 void* CodeHeap::find_block_for(void* p) const {
458 // Check the pointer to be in committed range.
459 if (!contains(p)) {
460 return NULL;
461 }
462
463 address seg_map = (address)_segmap.low();
464 size_t seg_idx = segment_for(p);
465
466 // This may happen in special cases. Just ignore.
467 // Example: PPC ICache stub generation.
468 if (is_segment_unused(seg_map[seg_idx])) {
469 return NULL;
470 }
471
472 // Iterate the segment map chain to find the start of the block.
473 while (seg_map[seg_idx] > 0) {
474 // Don't check each segment index to refer to a used segment.
475 // This method is called extremely often. Therefore, any checking
476 // has a significant impact on performance. Rely on CodeHeap::verify()
477 // to do the job on request.
478 seg_idx -= (int)seg_map[seg_idx];
479 }
480
481 return address_for(seg_idx);
482 }
483
484 // Find block which contains the passed pointer.
485 // The block must be used, i.e. must not be a FreeBlock.
486 // Return a pointer that points past the block header.
487 void* CodeHeap::find_start(void* p) const {
488 HeapBlock* h = (HeapBlock*)find_block_for(p);
489 return ((h == NULL) || h->free()) ? NULL : h->allocated_space();
490 }
491
492 // Find block which contains the passed pointer.
493 // Same as find_start(p), but with additional safety net.
494 CodeBlob* CodeHeap::find_blob_unsafe(void* start) const {
495 CodeBlob* result = (CodeBlob*)CodeHeap::find_start(start);
496 return (result != NULL && result->blob_contains((address)start)) ? result : NULL;
497 }
498
499 size_t CodeHeap::alignment_unit() const {
500 // this will be a power of two
501 return _segment_size;
502 }
503
504
505 size_t CodeHeap::alignment_offset() const {
506 // The lowest address in any allocated block will be
507 // equal to alignment_offset (mod alignment_unit).
508 return sizeof(HeapBlock) & (_segment_size - 1);
509 }
510
511 // Returns the current block if available and used.
512 // If not, it returns the subsequent block (if available), NULL otherwise.
513 // Free blocks are merged, therefore there is at most one free block
514 // between two used ones. As a result, the subsequent block (if available) is
515 // guaranteed to be used.
516 // The returned pointer points past the block header.
517 void* CodeHeap::next_used(HeapBlock* b) const {
518 if (b != NULL && b->free()) b = next_block(b);
519 assert(b == NULL || !b->free(), "must be in use or at end of heap");
520 return (b == NULL) ? NULL : b->allocated_space();
521 }
522
523 // Returns the first used HeapBlock
524 // The returned pointer points to the block header.
525 HeapBlock* CodeHeap::first_block() const {
526 if (_next_segment > 0)
527 return block_at(0);
528 return NULL;
529 }
530
531 // The returned pointer points to the block header.
532 HeapBlock* CodeHeap::block_start(void* q) const {
533 HeapBlock* b = (HeapBlock*)find_start(q);
534 if (b == NULL) return NULL;
535 return b - 1;
536 }
537
538 // Returns the next Heap block.
539 // The returned pointer points to the block header.
540 HeapBlock* CodeHeap::next_block(HeapBlock *b) const {
541 if (b == NULL) return NULL;
542 size_t i = segment_for(b) + b->length();
543 if (i < _next_segment)
544 return block_at(i);
545 return NULL;
546 }
547
548
549 // Returns current capacity
550 size_t CodeHeap::capacity() const {
551 return _memory.committed_size();
552 }
553
554 size_t CodeHeap::max_capacity() const {
555 return _memory.reserved_size();
556 }
557
558 int CodeHeap::allocated_segments() const {
559 return (int)_next_segment;
560 }
561
562 size_t CodeHeap::allocated_capacity() const {
563 // size of used heap - size on freelist
564 return segments_to_size(_next_segment - _freelist_segments);
565 }
566
567 // Returns size of the unallocated heap block
568 size_t CodeHeap::heap_unallocated_capacity() const {
569 // Total number of segments - number currently used
570 return segments_to_size(_number_of_reserved_segments - _next_segment);
571 }
572
573 // Free list management
574
575 FreeBlock* CodeHeap::following_block(FreeBlock *b) {
576 return (FreeBlock*)(((address)b) + _segment_size * b->length());
577 }
578
579 // Inserts block b after a
580 void CodeHeap::insert_after(FreeBlock* a, FreeBlock* b) {
581 assert(a != NULL && b != NULL, "must be real pointers");
582
583 // Link b into the list after a
584 b->set_link(a->link());
585 a->set_link(b);
586
587 // See if we can merge blocks
588 merge_right(b); // Try to make b bigger
589 merge_right(a); // Try to make a include b
590 }
591
592 // Try to merge this block with the following block
593 bool CodeHeap::merge_right(FreeBlock* a) {
594 assert(a->free(), "must be a free block");
595 if (following_block(a) == a->link()) {
596 assert(a->link() != NULL && a->link()->free(), "must be free too");
597
598 // Remember linked (following) block. invalidate should only zap header of this block.
599 size_t follower = segment_for(a->link());
600 // Merge block a to include the following block.
601 a->set_length(a->length() + a->link()->length());
602 a->set_link(a->link()->link());
603
604 // Update the segment map and invalidate block contents.
605 mark_segmap_as_used(follower, segment_for(a) + a->length(), true);
606 // Block contents has already been invalidated by add_to_freelist.
607 // What's left is the header of the following block which now is
608 // in the middle of the merged block. Just zap one segment.
609 invalidate(follower, follower + 1, 0);
610
611 _freelist_length--;
612 return true;
613 }
614 return false;
615 }
616
617
618 void CodeHeap::add_to_freelist(HeapBlock* a) {
619 FreeBlock* b = (FreeBlock*)a;
620 size_t bseg = segment_for(b);
621 _freelist_length++;
622
623 _blob_count--;
624 assert(_blob_count >= 0, "sanity");
625
626 assert(b != _freelist, "cannot be removed twice");
627
628 // Mark as free and update free space count
629 _freelist_segments += b->length();
630 b->set_free();
631 invalidate(bseg, bseg + b->length(), sizeof(FreeBlock));
632
633 // First element in list?
634 if (_freelist == NULL) {
635 b->set_link(NULL);
636 _freelist = b;
637 return;
638 }
639
640 // Since the freelist is ordered (smaller addresses -> larger addresses) and the
641 // element we want to insert into the freelist has a smaller address than the first
642 // element, we can simply add 'b' as the first element and we are done.
643 if (b < _freelist) {
644 // Insert first in list
645 b->set_link(_freelist);
646 _freelist = b;
647 merge_right(_freelist);
648 return;
649 }
650
651 // Scan for right place to put into list.
652 // List is sorted by increasing addresses.
653 FreeBlock* prev = _freelist;
654 FreeBlock* cur = _freelist->link();
655 if ((_freelist_length > freelist_limit) && (_last_insert_point != NULL)) {
656 _last_insert_point = (FreeBlock*)find_block_for(_last_insert_point);
657 if ((_last_insert_point != NULL) && _last_insert_point->free() && (_last_insert_point < b)) {
658 prev = _last_insert_point;
659 cur = prev->link();
660 }
661 }
662 while(cur != NULL && cur < b) {
663 assert(prev < cur, "Freelist must be ordered");
664 prev = cur;
665 cur = cur->link();
666 }
667 assert((prev < b) && (cur == NULL || b < cur), "free-list must be ordered");
668 insert_after(prev, b);
669 _last_insert_point = prev;
670 }
671
672 /**
673 * Search freelist for an entry on the list with the best fit.
674 * @return NULL, if no one was found
675 */
676 HeapBlock* CodeHeap::search_freelist(size_t length) {
677 FreeBlock* found_block = NULL;
678 FreeBlock* found_prev = NULL;
679 size_t found_length = _next_segment; // max it out to begin with
680
681 HeapBlock* res = NULL;
682 FreeBlock* prev = NULL;
683 FreeBlock* cur = _freelist;
684
685 length = length < CodeCacheMinBlockLength ? CodeCacheMinBlockLength : length;
686
687 // Search for best-fitting block
688 while(cur != NULL) {
689 size_t cur_length = cur->length();
690 if (cur_length == length) {
691 // We have a perfect fit
692 found_block = cur;
693 found_prev = prev;
694 found_length = cur_length;
695 break;
696 } else if ((cur_length > length) && (cur_length < found_length)) {
697 // This is a new, closer fit. Remember block, its previous element, and its length
698 found_block = cur;
699 found_prev = prev;
700 found_length = cur_length;
701 }
702 // Next element in list
703 prev = cur;
704 cur = cur->link();
705 }
706
707 if (found_block == NULL) {
708 // None found
709 return NULL;
710 }
711
712 // Exact (or at least good enough) fit. Remove from list.
713 // Don't leave anything on the freelist smaller than CodeCacheMinBlockLength.
714 if (found_length - length < CodeCacheMinBlockLength) {
715 _freelist_length--;
716 length = found_length;
717 if (found_prev == NULL) {
718 assert(_freelist == found_block, "sanity check");
719 _freelist = _freelist->link();
720 } else {
721 assert((found_prev->link() == found_block), "sanity check");
722 // Unmap element
723 found_prev->set_link(found_block->link());
724 }
725 res = (HeapBlock*)found_block;
726 // sizeof(HeapBlock) < sizeof(FreeBlock).
727 // Invalidate the additional space that FreeBlock occupies.
728 // The rest of the block should already be invalidated.
729 // This is necessary due to a dubious assert in nmethod.cpp(PcDescCache::reset_to()).
730 // Can't use invalidate() here because it works on segment_size units (too coarse).
731 DEBUG_ONLY(memset((void*)res->allocated_space(), badCodeHeapNewVal, sizeof(FreeBlock) - sizeof(HeapBlock)));
732 } else {
733 // Truncate the free block and return the truncated part
734 // as new HeapBlock. The remaining free block does not
735 // need to be updated, except for it's length. Truncating
736 // the segment map does not invalidate the leading part.
737 res = split_block(found_block, found_length - length);
738 }
739
740 res->set_used();
741 _freelist_segments -= length;
742 return res;
743 }
744
745 int CodeHeap::defrag_segmap(bool do_defrag) {
746 int extra_hops_used = 0;
747 int extra_hops_free = 0;
748 int blocks_used = 0;
749 int blocks_free = 0;
750 for(HeapBlock* h = first_block(); h != NULL; h = next_block(h)) {
751 size_t beg = segment_for(h);
752 size_t end = segment_for(h) + h->length();
753 int extra_hops = segmap_hops(beg, end);
754 if (h->free()) {
755 extra_hops_free += extra_hops;
756 blocks_free++;
757 } else {
758 extra_hops_used += extra_hops;
759 blocks_used++;
760 }
761 if (do_defrag && (extra_hops > 0)) {
762 mark_segmap_as_used(beg, end, false);
763 }
764 }
765 return extra_hops_used + extra_hops_free;
766 }
767
768 // Count the hops required to get from the last segment of a
769 // heap block to the block header segment. For the optimal case,
770 // #hops = ((#segments-1)+(free_sentinel-2))/(free_sentinel-1)
771 // The range of segments to be checked is given by [beg..end).
772 // Return the number of extra hops required. There may be extra hops
773 // due to the is_FreeBlock_join optimization in mark_segmap_as_used().
774 int CodeHeap::segmap_hops(size_t beg, size_t end) {
775 if (beg < end) {
776 // setup _segmap pointers for faster indexing
777 address p = (address)_segmap.low() + beg;
778 int hops_expected = (int)(((end-beg-1)+(free_sentinel-2))/(free_sentinel-1));
779 int nhops = 0;
780 size_t ix = end-beg-1;
781 while (p[ix] > 0) {
782 ix -= p[ix];
783 nhops++;
784 }
785 return (nhops > hops_expected) ? nhops - hops_expected : 0;
786 }
787 return 0;
788 }
789
790 //----------------------------------------------------------------------------
791 // Non-product code
792
793 #ifndef PRODUCT
794
795 void CodeHeap::print() {
796 tty->print_cr("The Heap");
797 }
798
799 void CodeHeap::verify() {
800 if (VerifyCodeCache) {
801 assert_locked_or_safepoint(CodeCache_lock);
802 size_t len = 0;
803 int count = 0;
804 for(FreeBlock* b = _freelist; b != NULL; b = b->link()) {
805 len += b->length();
806 count++;
807 // Check if we have merged all free blocks
808 assert(merge_right(b) == false, "Missed merging opportunity");
809 }
810 // Verify that freelist contains the right amount of free space
811 assert(len == _freelist_segments, "wrong freelist");
812
813 for(HeapBlock* h = first_block(); h != NULL; h = next_block(h)) {
814 if (h->free()) count--;
815 }
816 // Verify that the freelist contains the same number of blocks
817 // than free blocks found on the full list.
818 assert(count == 0, "missing free blocks");
819
820 //---< all free block memory must have been invalidated >---
821 for(FreeBlock* b = _freelist; b != NULL; b = b->link()) {
822 for (char* c = (char*)b + sizeof(FreeBlock); c < (char*)b + segments_to_size(b->length()); c++) {
823 assert(*c == (char)badCodeHeapNewVal, "FreeBlock@" PTR_FORMAT "(" PTR_FORMAT ") not invalidated @byte %d", p2i(b), b->length(), (int)(c - (char*)b));
824 }
825 }
826
827 address seg_map = (address)_segmap.low();
828 size_t nseg = 0;
829 int extra_hops = 0;
830 count = 0;
831 for(HeapBlock* b = first_block(); b != NULL; b = next_block(b)) {
832 size_t seg1 = segment_for(b);
833 size_t segn = seg1 + b->length();
834 extra_hops += segmap_hops(seg1, segn);
835 count++;
836 for (size_t i = seg1; i < segn; i++) {
837 nseg++;
838 //---< Verify segment map marking >---
839 // All allocated segments, no matter if in a free or used block,
840 // must be marked "in use".
841 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");
842 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]);
843 }
844 }
845 assert(nseg == _next_segment, "CodeHeap: segment count mismatch. found %d, expected %d.", (int)nseg, (int)_next_segment);
846 assert((count == 0) || (extra_hops < (16 + 2*count)), "CodeHeap: many extra hops due to optimization. blocks: %d, extra hops: %d.", count, extra_hops);
847
848 // Verify that the number of free blocks is not out of hand.
849 static int free_block_threshold = 10000;
850 if (count > free_block_threshold) {
851 warning("CodeHeap: # of free blocks > %d", free_block_threshold);
852 // Double the warning limit
853 free_block_threshold *= 2;
854 }
855 }
856 }
857
858 #endif