1 #ifdef USE_PRAGMA_IDENT_SRC
2 #pragma ident "@(#)tenuredGeneration.cpp 1.47 07/05/29 09:44:17 JVM"
3 #endif
4 /*
5 * Copyright 2001-2007 Sun Microsystems, Inc. All Rights Reserved.
6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
7 *
8 * This code is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License version 2 only, as
10 * published by the Free Software Foundation.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
23 * CA 95054 USA or visit www.sun.com if you need additional information or
24 * have any questions.
25 *
26 */
27
28 # include "incls/_precompiled.incl"
29 # include "incls/_tenuredGeneration.cpp.incl"
30
31 TenuredGeneration::TenuredGeneration(ReservedSpace rs,
32 size_t initial_byte_size, int level,
33 GenRemSet* remset) :
34 OneContigSpaceCardGeneration(rs, initial_byte_size,
35 MinHeapDeltaBytes, level, remset, NULL)
36 {
37 HeapWord* bottom = (HeapWord*) _virtual_space.low();
38 HeapWord* end = (HeapWord*) _virtual_space.high();
39 _the_space = new TenuredSpace(_bts, MemRegion(bottom, end));
40 _the_space->reset_saved_mark();
41 _shrink_factor = 0;
42 _capacity_at_prologue = 0;
43
44 _gc_stats = new GCStats();
45
46 // initialize performance counters
47
48 const char* gen_name = "old";
49
50 // Generation Counters -- generation 1, 1 subspace
51 _gen_counters = new GenerationCounters(gen_name, 1, 1, &_virtual_space);
52
53 _gc_counters = new CollectorCounters("MSC", 1);
54
55 _space_counters = new CSpaceCounters(gen_name, 0,
56 _virtual_space.reserved_size(),
57 _the_space, _gen_counters);
58 #ifndef SERIALGC
59 if (UseParNewGC && ParallelGCThreads > 0) {
60 typedef ParGCAllocBufferWithBOT* ParGCAllocBufferWithBOTPtr;
61 _alloc_buffers = NEW_C_HEAP_ARRAY(ParGCAllocBufferWithBOTPtr,
62 ParallelGCThreads);
63 if (_alloc_buffers == NULL)
64 vm_exit_during_initialization("Could not allocate alloc_buffers");
65 for (uint i = 0; i < ParallelGCThreads; i++) {
66 _alloc_buffers[i] =
67 new ParGCAllocBufferWithBOT(OldPLABSize, _bts);
68 if (_alloc_buffers[i] == NULL)
69 vm_exit_during_initialization("Could not allocate alloc_buffers");
70 }
71 } else {
72 _alloc_buffers = NULL;
73 }
74 #endif // SERIALGC
75 }
76
77
78 const char* TenuredGeneration::name() const {
79 return "tenured generation";
80 }
81
82 void TenuredGeneration::compute_new_size() {
83 assert(_shrink_factor <= 100, "invalid shrink factor");
84 size_t current_shrink_factor = _shrink_factor;
85 _shrink_factor = 0;
86
87 // We don't have floating point command-line arguments
88 // Note: argument processing ensures that MinHeapFreeRatio < 100.
89 const double minimum_free_percentage = MinHeapFreeRatio / 100.0;
90 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
91
92 // Compute some numbers about the state of the heap.
93 const size_t used_after_gc = used();
94 const size_t capacity_after_gc = capacity();
95
96 const double min_tmp = used_after_gc / maximum_used_percentage;
97 size_t minimum_desired_capacity = (size_t)MIN2(min_tmp, double(max_uintx));
98 // Don't shrink less than the initial generation size
99 minimum_desired_capacity = MAX2(minimum_desired_capacity,
100 spec()->init_size());
101 assert(used_after_gc <= minimum_desired_capacity, "sanity check");
102
103 if (PrintGC && Verbose) {
104 const size_t free_after_gc = free();
105 const double free_percentage = ((double)free_after_gc) / capacity_after_gc;
106 gclog_or_tty->print_cr("TenuredGeneration::compute_new_size: ");
107 gclog_or_tty->print_cr(" "
108 " minimum_free_percentage: %6.2f"
109 " maximum_used_percentage: %6.2f",
110 minimum_free_percentage,
111 maximum_used_percentage);
112 gclog_or_tty->print_cr(" "
113 " free_after_gc : %6.1fK"
114 " used_after_gc : %6.1fK"
115 " capacity_after_gc : %6.1fK",
116 free_after_gc / (double) K,
117 used_after_gc / (double) K,
118 capacity_after_gc / (double) K);
119 gclog_or_tty->print_cr(" "
120 " free_percentage: %6.2f",
121 free_percentage);
122 }
123
124 if (capacity_after_gc < minimum_desired_capacity) {
125 // If we have less free space than we want then expand
126 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
127 // Don't expand unless it's significant
128 if (expand_bytes >= _min_heap_delta_bytes) {
129 expand(expand_bytes, 0); // safe if expansion fails
130 }
131 if (PrintGC && Verbose) {
132 gclog_or_tty->print_cr(" expanding:"
133 " minimum_desired_capacity: %6.1fK"
134 " expand_bytes: %6.1fK"
135 " _min_heap_delta_bytes: %6.1fK",
136 minimum_desired_capacity / (double) K,
137 expand_bytes / (double) K,
138 _min_heap_delta_bytes / (double) K);
139 }
140 return;
141 }
142
143 // No expansion, now see if we want to shrink
144 size_t shrink_bytes = 0;
145 // We would never want to shrink more than this
146 size_t max_shrink_bytes = capacity_after_gc - minimum_desired_capacity;
147
148 if (MaxHeapFreeRatio < 100) {
149 const double maximum_free_percentage = MaxHeapFreeRatio / 100.0;
150 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
151 const double max_tmp = used_after_gc / minimum_used_percentage;
152 size_t maximum_desired_capacity = (size_t)MIN2(max_tmp, double(max_uintx));
153 maximum_desired_capacity = MAX2(maximum_desired_capacity,
154 spec()->init_size());
155 if (PrintGC && Verbose) {
156 gclog_or_tty->print_cr(" "
157 " maximum_free_percentage: %6.2f"
158 " minimum_used_percentage: %6.2f",
159 maximum_free_percentage,
160 minimum_used_percentage);
161 gclog_or_tty->print_cr(" "
162 " _capacity_at_prologue: %6.1fK"
163 " minimum_desired_capacity: %6.1fK"
164 " maximum_desired_capacity: %6.1fK",
165 _capacity_at_prologue / (double) K,
166 minimum_desired_capacity / (double) K,
167 maximum_desired_capacity / (double) K);
168 }
169 assert(minimum_desired_capacity <= maximum_desired_capacity,
170 "sanity check");
171
172 if (capacity_after_gc > maximum_desired_capacity) {
173 // Capacity too large, compute shrinking size
174 shrink_bytes = capacity_after_gc - maximum_desired_capacity;
175 // We don't want shrink all the way back to initSize if people call
176 // System.gc(), because some programs do that between "phases" and then
177 // we'd just have to grow the heap up again for the next phase. So we
178 // damp the shrinking: 0% on the first call, 10% on the second call, 40%
179 // on the third call, and 100% by the fourth call. But if we recompute
180 // size without shrinking, it goes back to 0%.
181 shrink_bytes = shrink_bytes / 100 * current_shrink_factor;
182 assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");
183 if (current_shrink_factor == 0) {
184 _shrink_factor = 10;
185 } else {
186 _shrink_factor = MIN2(current_shrink_factor * 4, (size_t) 100);
187 }
188 if (PrintGC && Verbose) {
189 gclog_or_tty->print_cr(" "
190 " shrinking:"
191 " initSize: %.1fK"
192 " maximum_desired_capacity: %.1fK",
193 spec()->init_size() / (double) K,
194 maximum_desired_capacity / (double) K);
195 gclog_or_tty->print_cr(" "
196 " shrink_bytes: %.1fK"
197 " current_shrink_factor: %d"
198 " new shrink factor: %d"
199 " _min_heap_delta_bytes: %.1fK",
200 shrink_bytes / (double) K,
201 current_shrink_factor,
202 _shrink_factor,
203 _min_heap_delta_bytes / (double) K);
204 }
205 }
206 }
207
208 if (capacity_after_gc > _capacity_at_prologue) {
209 // We might have expanded for promotions, in which case we might want to
210 // take back that expansion if there's room after GC. That keeps us from
211 // stretching the heap with promotions when there's plenty of room.
212 size_t expansion_for_promotion = capacity_after_gc - _capacity_at_prologue;
213 expansion_for_promotion = MIN2(expansion_for_promotion, max_shrink_bytes);
214 // We have two shrinking computations, take the largest
215 shrink_bytes = MAX2(shrink_bytes, expansion_for_promotion);
216 assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");
217 if (PrintGC && Verbose) {
218 gclog_or_tty->print_cr(" "
219 " aggressive shrinking:"
220 " _capacity_at_prologue: %.1fK"
221 " capacity_after_gc: %.1fK"
222 " expansion_for_promotion: %.1fK"
223 " shrink_bytes: %.1fK",
224 capacity_after_gc / (double) K,
225 _capacity_at_prologue / (double) K,
226 expansion_for_promotion / (double) K,
227 shrink_bytes / (double) K);
228 }
229 }
230 // Don't shrink unless it's significant
231 if (shrink_bytes >= _min_heap_delta_bytes) {
232 shrink(shrink_bytes);
233 }
234 assert(used() == used_after_gc && used_after_gc <= capacity(),
235 "sanity check");
236 }
237
238 void TenuredGeneration::gc_prologue(bool full) {
239 _capacity_at_prologue = capacity();
240 _used_at_prologue = used();
241 if (VerifyBeforeGC) {
242 verify_alloc_buffers_clean();
243 }
244 }
245
246 void TenuredGeneration::gc_epilogue(bool full) {
247 if (VerifyAfterGC) {
248 verify_alloc_buffers_clean();
249 }
250 OneContigSpaceCardGeneration::gc_epilogue(full);
251 }
252
253
254 bool TenuredGeneration::should_collect(bool full,
255 size_t size,
256 bool is_tlab) {
257 // This should be one big conditional or (||), but I want to be able to tell
258 // why it returns what it returns (without re-evaluating the conditionals
259 // in case they aren't idempotent), so I'm doing it this way.
260 // DeMorgan says it's okay.
261 bool result = false;
262 if (!result && full) {
263 result = true;
264 if (PrintGC && Verbose) {
265 gclog_or_tty->print_cr("TenuredGeneration::should_collect: because"
266 " full");
267 }
268 }
269 if (!result && should_allocate(size, is_tlab)) {
270 result = true;
271 if (PrintGC && Verbose) {
272 gclog_or_tty->print_cr("TenuredGeneration::should_collect: because"
273 " should_allocate(" SIZE_FORMAT ")",
274 size);
275 }
276 }
277 // If we don't have very much free space.
278 // XXX: 10000 should be a percentage of the capacity!!!
279 if (!result && free() < 10000) {
280 result = true;
281 if (PrintGC && Verbose) {
282 gclog_or_tty->print_cr("TenuredGeneration::should_collect: because"
283 " free(): " SIZE_FORMAT,
284 free());
285 }
286 }
287 // If we had to expand to accomodate promotions from younger generations
288 if (!result && _capacity_at_prologue < capacity()) {
289 result = true;
290 if (PrintGC && Verbose) {
291 gclog_or_tty->print_cr("TenuredGeneration::should_collect: because"
292 "_capacity_at_prologue: " SIZE_FORMAT " < capacity(): " SIZE_FORMAT,
293 _capacity_at_prologue, capacity());
294 }
295 }
296 return result;
297 }
298
299 void TenuredGeneration::collect(bool full,
300 bool clear_all_soft_refs,
301 size_t size,
302 bool is_tlab) {
303 retire_alloc_buffers_before_full_gc();
304 OneContigSpaceCardGeneration::collect(full, clear_all_soft_refs,
305 size, is_tlab);
306 }
307
308 void TenuredGeneration::update_gc_stats(int current_level,
309 bool full) {
310 // If the next lower level(s) has been collected, gather any statistics
311 // that are of interest at this point.
312 if (!full && (current_level + 1) == level()) {
313 // Calculate size of data promoted from the younger generations
314 // before doing the collection.
315 size_t used_before_gc = used();
316
317 // If the younger gen collections were skipped, then the
318 // number of promoted bytes will be 0 and adding it to the
319 // average will incorrectly lessen the average. It is, however,
320 // also possible that no promotion was needed.
321 if (used_before_gc >= _used_at_prologue) {
322 size_t promoted_in_bytes = used_before_gc - _used_at_prologue;
323 gc_stats()->avg_promoted()->sample(promoted_in_bytes);
324 }
325 }
326 }
327
328 void TenuredGeneration::update_counters() {
329 if (UsePerfData) {
330 _space_counters->update_all();
331 _gen_counters->update_all();
332 }
333 }
334
335
336 #ifndef SERIALGC
337 oop TenuredGeneration::par_promote(int thread_num,
338 oop old, markOop m, size_t word_sz) {
339
340 ParGCAllocBufferWithBOT* buf = _alloc_buffers[thread_num];
341 HeapWord* obj_ptr = buf->allocate(word_sz);
342 bool is_lab = true;
343 if (obj_ptr == NULL) {
344 #ifndef PRODUCT
345 if (Universe::heap()->promotion_should_fail()) {
346 return NULL;
347 }
348 #endif // #ifndef PRODUCT
349
350 // Slow path:
351 if (word_sz * 100 < ParallelGCBufferWastePct * buf->word_sz()) {
352 // Is small enough; abandon this buffer and start a new one.
353 size_t buf_size = buf->word_sz();
354 HeapWord* buf_space =
355 TenuredGeneration::par_allocate(buf_size, false);
356 if (buf_space == NULL) {
357 buf_space = expand_and_allocate(buf_size, false, true /* parallel*/);
358 }
359 if (buf_space != NULL) {
360 buf->retire(false, false);
361 buf->set_buf(buf_space);
362 obj_ptr = buf->allocate(word_sz);
363 assert(obj_ptr != NULL, "Buffer was definitely big enough...");
364 }
365 };
366 // Otherwise, buffer allocation failed; try allocating object
367 // individually.
368 if (obj_ptr == NULL) {
369 obj_ptr = TenuredGeneration::par_allocate(word_sz, false);
370 if (obj_ptr == NULL) {
371 obj_ptr = expand_and_allocate(word_sz, false, true /* parallel */);
372 }
373 }
374 if (obj_ptr == NULL) return NULL;
375 }
376 assert(obj_ptr != NULL, "program logic");
377 Copy::aligned_disjoint_words((HeapWord*)old, obj_ptr, word_sz);
378 oop obj = oop(obj_ptr);
379 // Restore the mark word copied above.
380 obj->set_mark(m);
381 return obj;
382 }
383
384 void TenuredGeneration::par_promote_alloc_undo(int thread_num,
385 HeapWord* obj,
386 size_t word_sz) {
387 ParGCAllocBufferWithBOT* buf = _alloc_buffers[thread_num];
388 if (buf->contains(obj)) {
389 guarantee(buf->contains(obj + word_sz - 1),
390 "should contain whole object");
391 buf->undo_allocation(obj, word_sz);
392 } else {
393 SharedHeap::fill_region_with_object(MemRegion(obj, word_sz));
394 }
395 }
396
397 void TenuredGeneration::par_promote_alloc_done(int thread_num) {
398 ParGCAllocBufferWithBOT* buf = _alloc_buffers[thread_num];
399 buf->retire(true, ParallelGCRetainPLAB);
400 }
401
402 void TenuredGeneration::retire_alloc_buffers_before_full_gc() {
403 if (UseParNewGC) {
404 for (uint i = 0; i < ParallelGCThreads; i++) {
405 _alloc_buffers[i]->retire(true /*end_of_gc*/, false /*retain*/);
406 }
407 }
408 }
409
410 // Verify that any retained parallel allocation buffers do not
411 // intersect with dirty cards.
412 void TenuredGeneration::verify_alloc_buffers_clean() {
413 if (UseParNewGC) {
414 for (uint i = 0; i < ParallelGCThreads; i++) {
415 _rs->verify_empty(_alloc_buffers[i]->range());
416 }
417 }
418 }
419 #else // SERIALGC
420 void TenuredGeneration::retire_alloc_buffers_before_full_gc() {}
421 void TenuredGeneration::verify_alloc_buffers_clean() {}
422 #endif // SERIALGC
423
424 bool TenuredGeneration::promotion_attempt_is_safe(
425 size_t max_promotion_in_bytes,
426 bool younger_handles_promotion_failure) const {
427
428 bool result = max_contiguous_available() >= max_promotion_in_bytes;
429
430 if (younger_handles_promotion_failure && !result) {
431 result = max_contiguous_available() >=
432 (size_t) gc_stats()->avg_promoted()->padded_average();
433 if (PrintGC && Verbose && result) {
434 gclog_or_tty->print_cr("TenuredGeneration::promotion_attempt_is_safe"
435 " contiguous_available: " SIZE_FORMAT
436 " avg_promoted: " SIZE_FORMAT,
437 max_contiguous_available(),
438 gc_stats()->avg_promoted()->padded_average());
439 }
440 } else {
441 if (PrintGC && Verbose) {
442 gclog_or_tty->print_cr("TenuredGeneration::promotion_attempt_is_safe"
443 " contiguous_available: " SIZE_FORMAT
444 " promotion_in_bytes: " SIZE_FORMAT,
445 max_contiguous_available(), max_promotion_in_bytes);
446 }
447 }
448 return result;
449 }