1 /*
2 * Copyright (c) 2001, 2009, 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 "incls/_precompiled.incl"
26 # include "incls/_tenuredGeneration.cpp.incl"
27
28 TenuredGeneration::TenuredGeneration(ReservedSpace rs,
29 size_t initial_byte_size, int level,
30 GenRemSet* remset) :
31 OneContigSpaceCardGeneration(rs, initial_byte_size,
32 MinHeapDeltaBytes, level, remset, NULL)
33 {
34 HeapWord* bottom = (HeapWord*) _virtual_space.low();
35 HeapWord* end = (HeapWord*) _virtual_space.high();
36 _the_space = new TenuredSpace(_bts, MemRegion(bottom, end));
37 _the_space->reset_saved_mark();
38 _shrink_factor = 0;
39 _capacity_at_prologue = 0;
40
41 _gc_stats = new GCStats();
42
43 // initialize performance counters
44
45 const char* gen_name = "old";
46
47 // Generation Counters -- generation 1, 1 subspace
48 _gen_counters = new GenerationCounters(gen_name, 1, 1, &_virtual_space);
49
50 _gc_counters = new CollectorCounters("MSC", 1);
51
52 _space_counters = new CSpaceCounters(gen_name, 0,
53 _virtual_space.reserved_size(),
54 _the_space, _gen_counters);
55 #ifndef SERIALGC
56 if (UseParNewGC && ParallelGCThreads > 0) {
57 typedef ParGCAllocBufferWithBOT* ParGCAllocBufferWithBOTPtr;
58 _alloc_buffers = NEW_C_HEAP_ARRAY(ParGCAllocBufferWithBOTPtr,
59 ParallelGCThreads);
60 if (_alloc_buffers == NULL)
61 vm_exit_during_initialization("Could not allocate alloc_buffers");
62 for (uint i = 0; i < ParallelGCThreads; i++) {
63 _alloc_buffers[i] =
64 new ParGCAllocBufferWithBOT(OldPLABSize, _bts);
65 if (_alloc_buffers[i] == NULL)
66 vm_exit_during_initialization("Could not allocate alloc_buffers");
67 }
68 } else {
69 _alloc_buffers = NULL;
70 }
71 #endif // SERIALGC
72 }
73
74
75 const char* TenuredGeneration::name() const {
76 return "tenured generation";
77 }
78
79 void TenuredGeneration::compute_new_size() {
80 assert(_shrink_factor <= 100, "invalid shrink factor");
81 size_t current_shrink_factor = _shrink_factor;
82 _shrink_factor = 0;
83
84 // We don't have floating point command-line arguments
85 // Note: argument processing ensures that MinHeapFreeRatio < 100.
86 const double minimum_free_percentage = MinHeapFreeRatio / 100.0;
87 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
88
89 // Compute some numbers about the state of the heap.
90 const size_t used_after_gc = used();
91 const size_t capacity_after_gc = capacity();
92
93 const double min_tmp = used_after_gc / maximum_used_percentage;
94 size_t minimum_desired_capacity = (size_t)MIN2(min_tmp, double(max_uintx));
95 // Don't shrink less than the initial generation size
96 minimum_desired_capacity = MAX2(minimum_desired_capacity,
97 spec()->init_size());
98 assert(used_after_gc <= minimum_desired_capacity, "sanity check");
99
100 if (PrintGC && Verbose) {
101 const size_t free_after_gc = free();
102 const double free_percentage = ((double)free_after_gc) / capacity_after_gc;
103 gclog_or_tty->print_cr("TenuredGeneration::compute_new_size: ");
104 gclog_or_tty->print_cr(" "
105 " minimum_free_percentage: %6.2f"
106 " maximum_used_percentage: %6.2f",
107 minimum_free_percentage,
108 maximum_used_percentage);
109 gclog_or_tty->print_cr(" "
110 " free_after_gc : %6.1fK"
111 " used_after_gc : %6.1fK"
112 " capacity_after_gc : %6.1fK",
113 free_after_gc / (double) K,
114 used_after_gc / (double) K,
115 capacity_after_gc / (double) K);
116 gclog_or_tty->print_cr(" "
117 " free_percentage: %6.2f",
118 free_percentage);
119 }
120
121 if (capacity_after_gc < minimum_desired_capacity) {
122 // If we have less free space than we want then expand
123 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
124 // Don't expand unless it's significant
125 if (expand_bytes >= _min_heap_delta_bytes) {
126 expand(expand_bytes, 0); // safe if expansion fails
127 }
128 if (PrintGC && Verbose) {
129 gclog_or_tty->print_cr(" expanding:"
130 " minimum_desired_capacity: %6.1fK"
131 " expand_bytes: %6.1fK"
132 " _min_heap_delta_bytes: %6.1fK",
133 minimum_desired_capacity / (double) K,
134 expand_bytes / (double) K,
135 _min_heap_delta_bytes / (double) K);
136 }
137 return;
138 }
139
140 // No expansion, now see if we want to shrink
141 size_t shrink_bytes = 0;
142 // We would never want to shrink more than this
143 size_t max_shrink_bytes = capacity_after_gc - minimum_desired_capacity;
144
145 if (MaxHeapFreeRatio < 100) {
146 const double maximum_free_percentage = MaxHeapFreeRatio / 100.0;
147 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
148 const double max_tmp = used_after_gc / minimum_used_percentage;
149 size_t maximum_desired_capacity = (size_t)MIN2(max_tmp, double(max_uintx));
150 maximum_desired_capacity = MAX2(maximum_desired_capacity,
151 spec()->init_size());
152 if (PrintGC && Verbose) {
153 gclog_or_tty->print_cr(" "
154 " maximum_free_percentage: %6.2f"
155 " minimum_used_percentage: %6.2f",
156 maximum_free_percentage,
157 minimum_used_percentage);
158 gclog_or_tty->print_cr(" "
159 " _capacity_at_prologue: %6.1fK"
160 " minimum_desired_capacity: %6.1fK"
161 " maximum_desired_capacity: %6.1fK",
162 _capacity_at_prologue / (double) K,
163 minimum_desired_capacity / (double) K,
164 maximum_desired_capacity / (double) K);
165 }
166 assert(minimum_desired_capacity <= maximum_desired_capacity,
167 "sanity check");
168
169 if (capacity_after_gc > maximum_desired_capacity) {
170 // Capacity too large, compute shrinking size
171 shrink_bytes = capacity_after_gc - maximum_desired_capacity;
172 // We don't want shrink all the way back to initSize if people call
173 // System.gc(), because some programs do that between "phases" and then
174 // we'd just have to grow the heap up again for the next phase. So we
175 // damp the shrinking: 0% on the first call, 10% on the second call, 40%
176 // on the third call, and 100% by the fourth call. But if we recompute
177 // size without shrinking, it goes back to 0%.
178 shrink_bytes = shrink_bytes / 100 * current_shrink_factor;
179 assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");
180 if (current_shrink_factor == 0) {
181 _shrink_factor = 10;
182 } else {
183 _shrink_factor = MIN2(current_shrink_factor * 4, (size_t) 100);
184 }
185 if (PrintGC && Verbose) {
186 gclog_or_tty->print_cr(" "
187 " shrinking:"
188 " initSize: %.1fK"
189 " maximum_desired_capacity: %.1fK",
190 spec()->init_size() / (double) K,
191 maximum_desired_capacity / (double) K);
192 gclog_or_tty->print_cr(" "
193 " shrink_bytes: %.1fK"
194 " current_shrink_factor: %d"
195 " new shrink factor: %d"
196 " _min_heap_delta_bytes: %.1fK",
197 shrink_bytes / (double) K,
198 current_shrink_factor,
199 _shrink_factor,
200 _min_heap_delta_bytes / (double) K);
201 }
202 }
203 }
204
205 if (capacity_after_gc > _capacity_at_prologue) {
206 // We might have expanded for promotions, in which case we might want to
207 // take back that expansion if there's room after GC. That keeps us from
208 // stretching the heap with promotions when there's plenty of room.
209 size_t expansion_for_promotion = capacity_after_gc - _capacity_at_prologue;
210 expansion_for_promotion = MIN2(expansion_for_promotion, max_shrink_bytes);
211 // We have two shrinking computations, take the largest
212 shrink_bytes = MAX2(shrink_bytes, expansion_for_promotion);
213 assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");
214 if (PrintGC && Verbose) {
215 gclog_or_tty->print_cr(" "
216 " aggressive shrinking:"
217 " _capacity_at_prologue: %.1fK"
218 " capacity_after_gc: %.1fK"
219 " expansion_for_promotion: %.1fK"
220 " shrink_bytes: %.1fK",
221 capacity_after_gc / (double) K,
222 _capacity_at_prologue / (double) K,
223 expansion_for_promotion / (double) K,
224 shrink_bytes / (double) K);
225 }
226 }
227 // Don't shrink unless it's significant
228 if (shrink_bytes >= _min_heap_delta_bytes) {
229 shrink(shrink_bytes);
230 }
231 assert(used() == used_after_gc && used_after_gc <= capacity(),
232 "sanity check");
233 }
234
235 void TenuredGeneration::gc_prologue(bool full) {
236 _capacity_at_prologue = capacity();
237 _used_at_prologue = used();
238 if (VerifyBeforeGC) {
239 verify_alloc_buffers_clean();
240 }
241 }
242
243 void TenuredGeneration::gc_epilogue(bool full) {
244 if (VerifyAfterGC) {
245 verify_alloc_buffers_clean();
246 }
247 OneContigSpaceCardGeneration::gc_epilogue(full);
248 }
249
250
251 bool TenuredGeneration::should_collect(bool full,
252 size_t size,
253 bool is_tlab) {
254 // This should be one big conditional or (||), but I want to be able to tell
255 // why it returns what it returns (without re-evaluating the conditionals
256 // in case they aren't idempotent), so I'm doing it this way.
257 // DeMorgan says it's okay.
258 bool result = false;
259 if (!result && full) {
260 result = true;
261 if (PrintGC && Verbose) {
262 gclog_or_tty->print_cr("TenuredGeneration::should_collect: because"
263 " full");
264 }
265 }
266 if (!result && should_allocate(size, is_tlab)) {
267 result = true;
268 if (PrintGC && Verbose) {
269 gclog_or_tty->print_cr("TenuredGeneration::should_collect: because"
270 " should_allocate(" SIZE_FORMAT ")",
271 size);
272 }
273 }
274 // If we don't have very much free space.
275 // XXX: 10000 should be a percentage of the capacity!!!
276 if (!result && free() < 10000) {
277 result = true;
278 if (PrintGC && Verbose) {
279 gclog_or_tty->print_cr("TenuredGeneration::should_collect: because"
280 " free(): " SIZE_FORMAT,
281 free());
282 }
283 }
284 // If we had to expand to accomodate promotions from younger generations
285 if (!result && _capacity_at_prologue < capacity()) {
286 result = true;
287 if (PrintGC && Verbose) {
288 gclog_or_tty->print_cr("TenuredGeneration::should_collect: because"
289 "_capacity_at_prologue: " SIZE_FORMAT " < capacity(): " SIZE_FORMAT,
290 _capacity_at_prologue, capacity());
291 }
292 }
293 return result;
294 }
295
296 void TenuredGeneration::collect(bool full,
297 bool clear_all_soft_refs,
298 size_t size,
299 bool is_tlab) {
300 retire_alloc_buffers_before_full_gc();
301 OneContigSpaceCardGeneration::collect(full, clear_all_soft_refs,
302 size, is_tlab);
303 }
304
305 void TenuredGeneration::update_gc_stats(int current_level,
306 bool full) {
307 // If the next lower level(s) has been collected, gather any statistics
308 // that are of interest at this point.
309 if (!full && (current_level + 1) == level()) {
310 // Calculate size of data promoted from the younger generations
311 // before doing the collection.
312 size_t used_before_gc = used();
313
314 // If the younger gen collections were skipped, then the
315 // number of promoted bytes will be 0 and adding it to the
316 // average will incorrectly lessen the average. It is, however,
317 // also possible that no promotion was needed.
318 if (used_before_gc >= _used_at_prologue) {
319 size_t promoted_in_bytes = used_before_gc - _used_at_prologue;
320 gc_stats()->avg_promoted()->sample(promoted_in_bytes);
321 }
322 }
323 }
324
325 void TenuredGeneration::update_counters() {
326 if (UsePerfData) {
327 _space_counters->update_all();
328 _gen_counters->update_all();
329 }
330 }
331
332
333 #ifndef SERIALGC
334 oop TenuredGeneration::par_promote(int thread_num,
335 oop old, markOop m, size_t word_sz) {
336
337 ParGCAllocBufferWithBOT* buf = _alloc_buffers[thread_num];
338 HeapWord* obj_ptr = buf->allocate(word_sz);
339 bool is_lab = true;
340 if (obj_ptr == NULL) {
341 #ifndef PRODUCT
342 if (Universe::heap()->promotion_should_fail()) {
343 return NULL;
344 }
345 #endif // #ifndef PRODUCT
346
347 // Slow path:
348 if (word_sz * 100 < ParallelGCBufferWastePct * buf->word_sz()) {
349 // Is small enough; abandon this buffer and start a new one.
350 size_t buf_size = buf->word_sz();
351 HeapWord* buf_space =
352 TenuredGeneration::par_allocate(buf_size, false);
353 if (buf_space == NULL) {
354 buf_space = expand_and_allocate(buf_size, false, true /* parallel*/);
355 }
356 if (buf_space != NULL) {
357 buf->retire(false, false);
358 buf->set_buf(buf_space);
359 obj_ptr = buf->allocate(word_sz);
360 assert(obj_ptr != NULL, "Buffer was definitely big enough...");
361 }
362 };
363 // Otherwise, buffer allocation failed; try allocating object
364 // individually.
365 if (obj_ptr == NULL) {
366 obj_ptr = TenuredGeneration::par_allocate(word_sz, false);
367 if (obj_ptr == NULL) {
368 obj_ptr = expand_and_allocate(word_sz, false, true /* parallel */);
369 }
370 }
371 if (obj_ptr == NULL) return NULL;
372 }
373 assert(obj_ptr != NULL, "program logic");
374 Copy::aligned_disjoint_words((HeapWord*)old, obj_ptr, word_sz);
375 oop obj = oop(obj_ptr);
376 // Restore the mark word copied above.
377 obj->set_mark(m);
378 return obj;
379 }
380
381 void TenuredGeneration::par_promote_alloc_undo(int thread_num,
382 HeapWord* obj,
383 size_t word_sz) {
384 ParGCAllocBufferWithBOT* buf = _alloc_buffers[thread_num];
385 if (buf->contains(obj)) {
386 guarantee(buf->contains(obj + word_sz - 1),
387 "should contain whole object");
388 buf->undo_allocation(obj, word_sz);
389 } else {
390 CollectedHeap::fill_with_object(obj, word_sz);
391 }
392 }
393
394 void TenuredGeneration::par_promote_alloc_done(int thread_num) {
395 ParGCAllocBufferWithBOT* buf = _alloc_buffers[thread_num];
396 buf->retire(true, ParallelGCRetainPLAB);
397 }
398
399 void TenuredGeneration::retire_alloc_buffers_before_full_gc() {
400 if (UseParNewGC) {
401 for (uint i = 0; i < ParallelGCThreads; i++) {
402 _alloc_buffers[i]->retire(true /*end_of_gc*/, false /*retain*/);
403 }
404 }
405 }
406
407 // Verify that any retained parallel allocation buffers do not
408 // intersect with dirty cards.
409 void TenuredGeneration::verify_alloc_buffers_clean() {
410 if (UseParNewGC) {
411 for (uint i = 0; i < ParallelGCThreads; i++) {
412 _rs->verify_aligned_region_empty(_alloc_buffers[i]->range());
413 }
414 }
415 }
416
417 #else // SERIALGC
418 void TenuredGeneration::retire_alloc_buffers_before_full_gc() {}
419 void TenuredGeneration::verify_alloc_buffers_clean() {}
420 #endif // SERIALGC
421
422 bool TenuredGeneration::promotion_attempt_is_safe(
423 size_t max_promotion_in_bytes,
424 bool younger_handles_promotion_failure) const {
425
426 bool result = max_contiguous_available() >= max_promotion_in_bytes;
427
428 if (younger_handles_promotion_failure && !result) {
429 result = max_contiguous_available() >=
430 (size_t) gc_stats()->avg_promoted()->padded_average();
431 if (PrintGC && Verbose && result) {
432 gclog_or_tty->print_cr("TenuredGeneration::promotion_attempt_is_safe"
433 " contiguous_available: " SIZE_FORMAT
434 " avg_promoted: " SIZE_FORMAT,
435 max_contiguous_available(),
436 gc_stats()->avg_promoted()->padded_average());
437 }
438 } else {
439 if (PrintGC && Verbose) {
440 gclog_or_tty->print_cr("TenuredGeneration::promotion_attempt_is_safe"
441 " contiguous_available: " SIZE_FORMAT
442 " promotion_in_bytes: " SIZE_FORMAT,
443 max_contiguous_available(), max_promotion_in_bytes);
444 }
445 }
446 return result;
447 }