1 /*
2 * Copyright (c) 2001, 2012, 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 "gc_implementation/shared/collectorCounters.hpp"
27 #include "gc_implementation/shared/parGCAllocBuffer.hpp"
28 #include "memory/allocation.inline.hpp"
29 #include "memory/blockOffsetTable.inline.hpp"
30 #include "memory/generation.inline.hpp"
31 #include "memory/generationSpec.hpp"
32 #include "memory/space.hpp"
33 #include "memory/tenuredGeneration.hpp"
34 #include "oops/oop.inline.hpp"
35 #include "runtime/java.hpp"
36
37 TenuredGeneration::TenuredGeneration(ReservedSpace rs,
38 size_t initial_byte_size, int level,
39 GenRemSet* remset) :
40 OneContigSpaceCardGeneration(rs, initial_byte_size,
41 MinHeapDeltaBytes, level, remset, NULL)
42 {
43 HeapWord* bottom = (HeapWord*) _virtual_space.low();
44 HeapWord* end = (HeapWord*) _virtual_space.high();
45 _the_space = new TenuredSpace(_bts, MemRegion(bottom, end));
46 _the_space->reset_saved_mark();
47 _shrink_factor = 0;
48 _capacity_at_prologue = 0;
49
50 _gc_stats = new GCStats();
51
52 // initialize performance counters
53
54 const char* gen_name = "old";
55
56 // Generation Counters -- generation 1, 1 subspace
57 _gen_counters = new GenerationCounters(gen_name, 1, 1, &_virtual_space);
58
59 _gc_counters = new CollectorCounters("MSC", 1);
60
61 _space_counters = new CSpaceCounters(gen_name, 0,
62 _virtual_space.reserved_size(),
63 _the_space, _gen_counters);
64 #ifndef SERIALGC
65 if (UseParNewGC) {
66 typedef ParGCAllocBufferWithBOT* ParGCAllocBufferWithBOTPtr;
67 _alloc_buffers = NEW_C_HEAP_ARRAY(ParGCAllocBufferWithBOTPtr,
68 ParallelGCThreads, mtGC);
69 if (_alloc_buffers == NULL)
70 vm_exit_during_initialization("Could not allocate alloc_buffers");
71 for (uint i = 0; i < ParallelGCThreads; i++) {
72 _alloc_buffers[i] =
73 new ParGCAllocBufferWithBOT(OldPLABSize, _bts);
74 if (_alloc_buffers[i] == NULL)
75 vm_exit_during_initialization("Could not allocate alloc_buffers");
76 }
77 } else {
78 _alloc_buffers = NULL;
79 }
80 #endif // SERIALGC
81 }
82
83
84 const char* TenuredGeneration::name() const {
85 return "tenured generation";
86 }
87
88 void TenuredGeneration::compute_new_size() {
89 assert(_shrink_factor <= 100, "invalid shrink factor");
90 size_t current_shrink_factor = _shrink_factor;
91 _shrink_factor = 0;
92
93 // We don't have floating point command-line arguments
94 // Note: argument processing ensures that MinHeapFreeRatio < 100.
95 const double minimum_free_percentage = MinHeapFreeRatio / 100.0;
96 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
97
98 // Compute some numbers about the state of the heap.
99 const size_t used_after_gc = used();
100 const size_t capacity_after_gc = capacity();
101
102 const double min_tmp = used_after_gc / maximum_used_percentage;
103 size_t minimum_desired_capacity = (size_t)MIN2(min_tmp, double(max_uintx));
104 // Don't shrink less than the initial generation size
105 minimum_desired_capacity = MAX2(minimum_desired_capacity,
106 spec()->init_size());
107 assert(used_after_gc <= minimum_desired_capacity, "sanity check");
108
109 if (PrintGC && Verbose) {
110 const size_t free_after_gc = free();
111 const double free_percentage = ((double)free_after_gc) / capacity_after_gc;
112 gclog_or_tty->print_cr("TenuredGeneration::compute_new_size: ");
113 gclog_or_tty->print_cr(" "
114 " minimum_free_percentage: %6.2f"
115 " maximum_used_percentage: %6.2f",
116 minimum_free_percentage,
117 maximum_used_percentage);
118 gclog_or_tty->print_cr(" "
119 " free_after_gc : %6.1fK"
120 " used_after_gc : %6.1fK"
121 " capacity_after_gc : %6.1fK",
122 free_after_gc / (double) K,
123 used_after_gc / (double) K,
124 capacity_after_gc / (double) K);
125 gclog_or_tty->print_cr(" "
126 " free_percentage: %6.2f",
127 free_percentage);
128 }
129
130 if (capacity_after_gc < minimum_desired_capacity) {
131 // If we have less free space than we want then expand
132 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
133 // Don't expand unless it's significant
134 if (expand_bytes >= _min_heap_delta_bytes) {
135 expand(expand_bytes, 0); // safe if expansion fails
136 }
137 if (PrintGC && Verbose) {
138 gclog_or_tty->print_cr(" expanding:"
139 " minimum_desired_capacity: %6.1fK"
140 " expand_bytes: %6.1fK"
141 " _min_heap_delta_bytes: %6.1fK",
142 minimum_desired_capacity / (double) K,
143 expand_bytes / (double) K,
144 _min_heap_delta_bytes / (double) K);
145 }
146 return;
147 }
148
149 // No expansion, now see if we want to shrink
150 size_t shrink_bytes = 0;
151 // We would never want to shrink more than this
152 size_t max_shrink_bytes = capacity_after_gc - minimum_desired_capacity;
153
154 if (MaxHeapFreeRatio < 100) {
155 const double maximum_free_percentage = MaxHeapFreeRatio / 100.0;
156 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
157 const double max_tmp = used_after_gc / minimum_used_percentage;
158 size_t maximum_desired_capacity = (size_t)MIN2(max_tmp, double(max_uintx));
159 maximum_desired_capacity = MAX2(maximum_desired_capacity,
160 spec()->init_size());
161 if (PrintGC && Verbose) {
162 gclog_or_tty->print_cr(" "
163 " maximum_free_percentage: %6.2f"
164 " minimum_used_percentage: %6.2f",
165 maximum_free_percentage,
166 minimum_used_percentage);
167 gclog_or_tty->print_cr(" "
168 " _capacity_at_prologue: %6.1fK"
169 " minimum_desired_capacity: %6.1fK"
170 " maximum_desired_capacity: %6.1fK",
171 _capacity_at_prologue / (double) K,
172 minimum_desired_capacity / (double) K,
173 maximum_desired_capacity / (double) K);
174 }
175 assert(minimum_desired_capacity <= maximum_desired_capacity,
176 "sanity check");
177
178 if (capacity_after_gc > maximum_desired_capacity) {
179 // Capacity too large, compute shrinking size
180 shrink_bytes = capacity_after_gc - maximum_desired_capacity;
181 // We don't want shrink all the way back to initSize if people call
182 // System.gc(), because some programs do that between "phases" and then
183 // we'd just have to grow the heap up again for the next phase. So we
184 // damp the shrinking: 0% on the first call, 10% on the second call, 40%
185 // on the third call, and 100% by the fourth call. But if we recompute
186 // size without shrinking, it goes back to 0%.
187 shrink_bytes = shrink_bytes / 100 * current_shrink_factor;
188 assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");
189 if (current_shrink_factor == 0) {
190 _shrink_factor = 10;
191 } else {
192 _shrink_factor = MIN2(current_shrink_factor * 4, (size_t) 100);
193 }
194 if (PrintGC && Verbose) {
195 gclog_or_tty->print_cr(" "
196 " shrinking:"
197 " initSize: %.1fK"
198 " maximum_desired_capacity: %.1fK",
199 spec()->init_size() / (double) K,
200 maximum_desired_capacity / (double) K);
201 gclog_or_tty->print_cr(" "
202 " shrink_bytes: %.1fK"
203 " current_shrink_factor: %d"
204 " new shrink factor: %d"
205 " _min_heap_delta_bytes: %.1fK",
206 shrink_bytes / (double) K,
207 current_shrink_factor,
208 _shrink_factor,
209 _min_heap_delta_bytes / (double) K);
210 }
211 }
212 }
213
214 if (capacity_after_gc > _capacity_at_prologue) {
215 // We might have expanded for promotions, in which case we might want to
216 // take back that expansion if there's room after GC. That keeps us from
217 // stretching the heap with promotions when there's plenty of room.
218 size_t expansion_for_promotion = capacity_after_gc - _capacity_at_prologue;
219 expansion_for_promotion = MIN2(expansion_for_promotion, max_shrink_bytes);
220 // We have two shrinking computations, take the largest
221 shrink_bytes = MAX2(shrink_bytes, expansion_for_promotion);
222 assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");
223 if (PrintGC && Verbose) {
224 gclog_or_tty->print_cr(" "
225 " aggressive shrinking:"
226 " _capacity_at_prologue: %.1fK"
227 " capacity_after_gc: %.1fK"
228 " expansion_for_promotion: %.1fK"
229 " shrink_bytes: %.1fK",
230 capacity_after_gc / (double) K,
231 _capacity_at_prologue / (double) K,
232 expansion_for_promotion / (double) K,
233 shrink_bytes / (double) K);
234 }
235 }
236 // Don't shrink unless it's significant
237 if (shrink_bytes >= _min_heap_delta_bytes) {
238 shrink(shrink_bytes);
239 }
240 assert(used() == used_after_gc && used_after_gc <= capacity(),
241 "sanity check");
242 }
243
244 void TenuredGeneration::gc_prologue(bool full) {
245 _capacity_at_prologue = capacity();
246 _used_at_prologue = used();
247 if (VerifyBeforeGC) {
248 verify_alloc_buffers_clean();
249 }
250 }
251
252 void TenuredGeneration::gc_epilogue(bool full) {
253 if (VerifyAfterGC) {
254 verify_alloc_buffers_clean();
255 }
256 OneContigSpaceCardGeneration::gc_epilogue(full);
257 }
258
259
260 bool TenuredGeneration::should_collect(bool full,
261 size_t size,
262 bool is_tlab) {
263 // This should be one big conditional or (||), but I want to be able to tell
264 // why it returns what it returns (without re-evaluating the conditionals
265 // in case they aren't idempotent), so I'm doing it this way.
266 // DeMorgan says it's okay.
267 bool result = false;
268 if (!result && full) {
269 result = true;
270 if (PrintGC && Verbose) {
271 gclog_or_tty->print_cr("TenuredGeneration::should_collect: because"
272 " full");
273 }
274 }
275 if (!result && should_allocate(size, is_tlab)) {
276 result = true;
277 if (PrintGC && Verbose) {
278 gclog_or_tty->print_cr("TenuredGeneration::should_collect: because"
279 " should_allocate(" SIZE_FORMAT ")",
280 size);
281 }
282 }
283 // If we don't have very much free space.
284 // XXX: 10000 should be a percentage of the capacity!!!
285 if (!result && free() < 10000) {
286 result = true;
287 if (PrintGC && Verbose) {
288 gclog_or_tty->print_cr("TenuredGeneration::should_collect: because"
289 " free(): " SIZE_FORMAT,
290 free());
291 }
292 }
293 // If we had to expand to accomodate promotions from younger generations
294 if (!result && _capacity_at_prologue < capacity()) {
295 result = true;
296 if (PrintGC && Verbose) {
297 gclog_or_tty->print_cr("TenuredGeneration::should_collect: because"
298 "_capacity_at_prologue: " SIZE_FORMAT " < capacity(): " SIZE_FORMAT,
299 _capacity_at_prologue, capacity());
300 }
301 }
302 return result;
303 }
304
305 void TenuredGeneration::collect(bool full,
306 bool clear_all_soft_refs,
307 size_t size,
308 bool is_tlab) {
309 retire_alloc_buffers_before_full_gc();
310 OneContigSpaceCardGeneration::collect(full, clear_all_soft_refs,
311 size, is_tlab);
312 }
313
314 void TenuredGeneration::update_gc_stats(int current_level,
315 bool full) {
316 // If the next lower level(s) has been collected, gather any statistics
317 // that are of interest at this point.
318 if (!full && (current_level + 1) == level()) {
319 // Calculate size of data promoted from the younger generations
320 // before doing the collection.
321 size_t used_before_gc = used();
322
323 // If the younger gen collections were skipped, then the
324 // number of promoted bytes will be 0 and adding it to the
325 // average will incorrectly lessen the average. It is, however,
326 // also possible that no promotion was needed.
327 if (used_before_gc >= _used_at_prologue) {
328 size_t promoted_in_bytes = used_before_gc - _used_at_prologue;
329 gc_stats()->avg_promoted()->sample(promoted_in_bytes);
330 }
331 }
332 }
333
334 void TenuredGeneration::update_counters() {
335 if (UsePerfData) {
336 _space_counters->update_all();
337 _gen_counters->update_all();
338 }
339 }
340
341
342 #ifndef SERIALGC
343 oop TenuredGeneration::par_promote(int thread_num,
344 oop old, markOop m, size_t word_sz) {
345
346 ParGCAllocBufferWithBOT* buf = _alloc_buffers[thread_num];
347 HeapWord* obj_ptr = buf->allocate(word_sz);
348 bool is_lab = true;
349 if (obj_ptr == NULL) {
350 #ifndef PRODUCT
351 if (Universe::heap()->promotion_should_fail()) {
352 return NULL;
353 }
354 #endif // #ifndef PRODUCT
355
356 // Slow path:
357 if (word_sz * 100 < ParallelGCBufferWastePct * buf->word_sz()) {
358 // Is small enough; abandon this buffer and start a new one.
359 size_t buf_size = buf->word_sz();
360 HeapWord* buf_space =
361 TenuredGeneration::par_allocate(buf_size, false);
362 if (buf_space == NULL) {
363 buf_space = expand_and_allocate(buf_size, false, true /* parallel*/);
364 }
365 if (buf_space != NULL) {
366 buf->retire(false, false);
367 buf->set_buf(buf_space);
368 obj_ptr = buf->allocate(word_sz);
369 assert(obj_ptr != NULL, "Buffer was definitely big enough...");
370 }
371 };
372 // Otherwise, buffer allocation failed; try allocating object
373 // individually.
374 if (obj_ptr == NULL) {
375 obj_ptr = TenuredGeneration::par_allocate(word_sz, false);
376 if (obj_ptr == NULL) {
377 obj_ptr = expand_and_allocate(word_sz, false, true /* parallel */);
378 }
379 }
380 if (obj_ptr == NULL) return NULL;
381 }
382 assert(obj_ptr != NULL, "program logic");
383 Copy::aligned_disjoint_words((HeapWord*)old, obj_ptr, word_sz);
384 oop obj = oop(obj_ptr);
385 // Restore the mark word copied above.
386 obj->set_mark(m);
387 return obj;
388 }
389
390 void TenuredGeneration::par_promote_alloc_undo(int thread_num,
391 HeapWord* obj,
392 size_t word_sz) {
393 ParGCAllocBufferWithBOT* buf = _alloc_buffers[thread_num];
394 if (buf->contains(obj)) {
395 guarantee(buf->contains(obj + word_sz - 1),
396 "should contain whole object");
397 buf->undo_allocation(obj, word_sz);
398 } else {
399 CollectedHeap::fill_with_object(obj, word_sz);
400 }
401 }
402
403 void TenuredGeneration::par_promote_alloc_done(int thread_num) {
404 ParGCAllocBufferWithBOT* buf = _alloc_buffers[thread_num];
405 buf->retire(true, ParallelGCRetainPLAB);
406 }
407
408 void TenuredGeneration::retire_alloc_buffers_before_full_gc() {
409 if (UseParNewGC) {
410 for (uint i = 0; i < ParallelGCThreads; i++) {
411 _alloc_buffers[i]->retire(true /*end_of_gc*/, false /*retain*/);
412 }
413 }
414 }
415
416 // Verify that any retained parallel allocation buffers do not
417 // intersect with dirty cards.
418 void TenuredGeneration::verify_alloc_buffers_clean() {
419 if (UseParNewGC) {
420 for (uint i = 0; i < ParallelGCThreads; i++) {
421 _rs->verify_aligned_region_empty(_alloc_buffers[i]->range());
422 }
423 }
424 }
425
426 #else // SERIALGC
427 void TenuredGeneration::retire_alloc_buffers_before_full_gc() {}
428 void TenuredGeneration::verify_alloc_buffers_clean() {}
429 #endif // SERIALGC
430
431 bool TenuredGeneration::promotion_attempt_is_safe(size_t max_promotion_in_bytes) const {
432 size_t available = max_contiguous_available();
433 size_t av_promo = (size_t)gc_stats()->avg_promoted()->padded_average();
434 bool res = (available >= av_promo) || (available >= max_promotion_in_bytes);
435 if (PrintGC && Verbose) {
436 gclog_or_tty->print_cr(
437 "Tenured: promo attempt is%s safe: available("SIZE_FORMAT") %s av_promo("SIZE_FORMAT"),"
438 "max_promo("SIZE_FORMAT")",
439 res? "":" not", available, res? ">=":"<",
440 av_promo, max_promotion_in_bytes);
441 }
442 return res;
443 }