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/shared/adaptiveSizePolicy.hpp"
27 #include "gc/shared/collectorPolicy.hpp"
28 #include "gc/shared/gcCause.hpp"
29 #include "gc/shared/workgroup.hpp"
30 #include "runtime/timer.hpp"
31 #include "utilities/ostream.hpp"
32 elapsedTimer AdaptiveSizePolicy::_minor_timer;
33 elapsedTimer AdaptiveSizePolicy::_major_timer;
34 bool AdaptiveSizePolicy::_debug_perturbation = false;
35
36 // The throughput goal is implemented as
37 // _throughput_goal = 1 - ( 1 / (1 + gc_cost_ratio))
38 // gc_cost_ratio is the ratio
39 // application cost / gc cost
40 // For example a gc_cost_ratio of 4 translates into a
41 // throughput goal of .80
42
43 AdaptiveSizePolicy::AdaptiveSizePolicy(size_t init_eden_size,
44 size_t init_promo_size,
45 size_t init_survivor_size,
46 double gc_pause_goal_sec,
47 uint gc_cost_ratio) :
48 _eden_size(init_eden_size),
49 _promo_size(init_promo_size),
149 if (ForceDynamicNumberOfGCThreads) {
150 // Assume this is debugging and jiggle the number of GC threads.
151 if (new_active_workers == prev_active_workers) {
152 if (new_active_workers < total_workers) {
153 new_active_workers++;
154 } else if (new_active_workers > min_workers) {
155 new_active_workers--;
156 }
157 }
158 if (new_active_workers == total_workers) {
159 if (_debug_perturbation) {
160 new_active_workers = min_workers;
161 }
162 _debug_perturbation = !_debug_perturbation;
163 }
164 assert((new_active_workers <= ParallelGCThreads) &&
165 (new_active_workers >= min_workers),
166 "Jiggled active workers too much");
167 }
168
169 if (TraceDynamicGCThreads) {
170 gclog_or_tty->print_cr("GCTaskManager::calc_default_active_workers() : "
171 "active_workers(): " UINTX_FORMAT " new_active_workers: " UINTX_FORMAT " "
172 "prev_active_workers: " UINTX_FORMAT "\n"
173 " active_workers_by_JT: " UINTX_FORMAT " active_workers_by_heap_size: " UINTX_FORMAT,
174 active_workers, new_active_workers, prev_active_workers,
175 active_workers_by_JT, active_workers_by_heap_size);
176 }
177 assert(new_active_workers > 0, "Always need at least 1");
178 return new_active_workers;
179 }
180
181 uint AdaptiveSizePolicy::calc_active_workers(uintx total_workers,
182 uintx active_workers,
183 uintx application_workers) {
184 // If the user has specifically set the number of
185 // GC threads, use them.
186
187 // If the user has turned off using a dynamic number of GC threads
188 // or the users has requested a specific number, set the active
189 // number of workers to all the workers.
190
191 uint new_active_workers;
192 if (!UseDynamicNumberOfGCThreads ||
193 (!FLAG_IS_DEFAULT(ParallelGCThreads) && !ForceDynamicNumberOfGCThreads)) {
194 new_active_workers = total_workers;
195 } else {
196 uintx min_workers = (total_workers == 1) ? 1 : 2;
258 (minor_pause_in_seconds > 0.0)) {
259 double interval_in_seconds =
260 _latest_minor_mutator_interval_seconds + minor_pause_in_seconds;
261 collection_cost =
262 minor_pause_in_seconds / interval_in_seconds;
263 _avg_minor_gc_cost->sample(collection_cost);
264 // Sample for performance counter
265 _avg_minor_interval->sample(interval_in_seconds);
266 }
267
268 // The policy does not have enough data until at least some
269 // young collections have been done.
270 _young_gen_policy_is_ready =
271 (_avg_minor_gc_cost->count() >= AdaptiveSizePolicyReadyThreshold);
272
273 // Calculate variables used to estimate pause time vs. gen sizes
274 double eden_size_in_mbytes = ((double)_eden_size) / ((double)M);
275 update_minor_pause_young_estimator(minor_pause_in_ms);
276 update_minor_pause_old_estimator(minor_pause_in_ms);
277
278 if (PrintAdaptiveSizePolicy && Verbose) {
279 gclog_or_tty->print("AdaptiveSizePolicy::minor_collection_end: "
280 "minor gc cost: %f average: %f", collection_cost,
281 _avg_minor_gc_cost->average());
282 gclog_or_tty->print_cr(" minor pause: %f minor period %f",
283 minor_pause_in_ms,
284 _latest_minor_mutator_interval_seconds * MILLIUNITS);
285 }
286
287 // Calculate variable used to estimate collection cost vs. gen sizes
288 assert(collection_cost >= 0.0, "Expected to be non-negative");
289 _minor_collection_estimator->update(eden_size_in_mbytes, collection_cost);
290 }
291
292 // Interval times use this timer to measure the mutator time.
293 // Reset the timer after the GC pause.
294 _minor_timer.reset();
295 _minor_timer.start();
296 }
297
298 size_t AdaptiveSizePolicy::eden_increment(size_t cur_eden, uint percent_change) {
299 size_t eden_heap_delta;
300 eden_heap_delta = cur_eden / 100 * percent_change;
301 return eden_heap_delta;
302 }
303
304 size_t AdaptiveSizePolicy::eden_increment(size_t cur_eden) {
305 return eden_increment(cur_eden, YoungGenerationSizeIncrement);
371 // small. Use the decaying gc cost only to decide whether to
372 // adjust for throughput. Using it also to determine the adjustment
373 // to be made for throughput also seems reasonable but there is
374 // no test case to use to decide if it is the right thing to do
375 // don't do it yet.
376
377 double AdaptiveSizePolicy::decaying_gc_cost() const {
378 double decayed_major_gc_cost = major_gc_cost();
379 double avg_major_interval = major_gc_interval_average_for_decay();
380 if (UseAdaptiveSizeDecayMajorGCCost &&
381 (AdaptiveSizeMajorGCDecayTimeScale > 0) &&
382 (avg_major_interval > 0.00)) {
383 double time_since_last_major_gc = time_since_major_gc();
384
385 // Decay the major gc cost?
386 if (time_since_last_major_gc >
387 ((double) AdaptiveSizeMajorGCDecayTimeScale) * avg_major_interval) {
388
389 // Decay using the time-since-last-major-gc
390 decayed_major_gc_cost = decaying_major_gc_cost();
391 if (PrintGCDetails && Verbose) {
392 gclog_or_tty->print_cr("\ndecaying_gc_cost: major interval average:"
393 " %f time since last major gc: %f",
394 avg_major_interval, time_since_last_major_gc);
395 gclog_or_tty->print_cr(" major gc cost: %f decayed major gc cost: %f",
396 major_gc_cost(), decayed_major_gc_cost);
397 }
398 }
399 }
400 double result = MIN2(1.0, decayed_major_gc_cost + minor_gc_cost());
401 return result;
402 }
403
404
405 void AdaptiveSizePolicy::clear_generation_free_space_flags() {
406 set_change_young_gen_for_min_pauses(0);
407 set_change_old_gen_for_maj_pauses(0);
408
409 set_change_old_gen_for_throughput(0);
410 set_change_young_gen_for_throughput(0);
411 set_decrease_for_footprint(0);
412 set_decide_at_full_gc(0);
413 }
414
415 void AdaptiveSizePolicy::check_gc_overhead_limit(
416 size_t young_live,
417 size_t eden_live,
418 size_t max_old_gen_size,
419 size_t max_eden_size,
444 // space has suddenly jumped up). If the current is much
445 // higher than the average, use the average since it represents
446 // the longer term behavior.
447 const size_t live_in_eden =
448 MIN2(eden_live, (size_t) avg_eden_live()->average());
449 const size_t free_in_eden = max_eden_size > live_in_eden ?
450 max_eden_size - live_in_eden : 0;
451 const size_t free_in_old_gen = (size_t)(max_old_gen_size - avg_old_live()->average());
452 const size_t total_free_limit = free_in_old_gen + free_in_eden;
453 const size_t total_mem = max_old_gen_size + max_eden_size;
454 const double mem_free_limit = total_mem * (GCHeapFreeLimit/100.0);
455 const double mem_free_old_limit = max_old_gen_size * (GCHeapFreeLimit/100.0);
456 const double mem_free_eden_limit = max_eden_size * (GCHeapFreeLimit/100.0);
457 const double gc_cost_limit = GCTimeLimit/100.0;
458 size_t promo_limit = (size_t)(max_old_gen_size - avg_old_live()->average());
459 // But don't force a promo size below the current promo size. Otherwise,
460 // the promo size will shrink for no good reason.
461 promo_limit = MAX2(promo_limit, _promo_size);
462
463
464 if (PrintAdaptiveSizePolicy && (Verbose ||
465 (free_in_old_gen < (size_t) mem_free_old_limit &&
466 free_in_eden < (size_t) mem_free_eden_limit))) {
467 gclog_or_tty->print_cr(
468 "PSAdaptiveSizePolicy::check_gc_overhead_limit:"
469 " promo_limit: " SIZE_FORMAT
470 " max_eden_size: " SIZE_FORMAT
471 " total_free_limit: " SIZE_FORMAT
472 " max_old_gen_size: " SIZE_FORMAT
473 " max_eden_size: " SIZE_FORMAT
474 " mem_free_limit: " SIZE_FORMAT,
475 promo_limit, max_eden_size, total_free_limit,
476 max_old_gen_size, max_eden_size,
477 (size_t) mem_free_limit);
478 }
479
480 bool print_gc_overhead_limit_would_be_exceeded = false;
481 if (is_full_gc) {
482 if (gc_cost() > gc_cost_limit &&
483 free_in_old_gen < (size_t) mem_free_old_limit &&
484 free_in_eden < (size_t) mem_free_eden_limit) {
485 // Collections, on average, are taking too much time, and
486 // gc_cost() > gc_cost_limit
487 // we have too little space available after a full gc.
488 // total_free_limit < mem_free_limit
489 // where
490 // total_free_limit is the free space available in
491 // both generations
492 // total_mem is the total space available for allocation
493 // in both generations (survivor spaces are not included
494 // just as they are not included in eden_limit).
495 // mem_free_limit is a fraction of total_mem judged to be an
496 // acceptable amount that is still unused.
497 // The heap can ask for the value of this variable when deciding
498 // whether to thrown an OutOfMemory error.
504 // At this point the GC overhead limit is being exceeded.
505 inc_gc_overhead_limit_count();
506 if (UseGCOverheadLimit) {
507 if (gc_overhead_limit_count() >=
508 AdaptiveSizePolicyGCTimeLimitThreshold){
509 // All conditions have been met for throwing an out-of-memory
510 set_gc_overhead_limit_exceeded(true);
511 // Avoid consecutive OOM due to the gc time limit by resetting
512 // the counter.
513 reset_gc_overhead_limit_count();
514 } else {
515 // The required consecutive collections which exceed the
516 // GC time limit may or may not have been reached. We
517 // are approaching that condition and so as not to
518 // throw an out-of-memory before all SoftRef's have been
519 // cleared, set _should_clear_all_soft_refs in CollectorPolicy.
520 // The clearing will be done on the next GC.
521 bool near_limit = gc_overhead_limit_near();
522 if (near_limit) {
523 collector_policy->set_should_clear_all_soft_refs(true);
524 if (PrintGCDetails && Verbose) {
525 gclog_or_tty->print_cr(" Nearing GC overhead limit, "
526 "will be clearing all SoftReference");
527 }
528 }
529 }
530 }
531 // Set this even when the overhead limit will not
532 // cause an out-of-memory. Diagnostic message indicating
533 // that the overhead limit is being exceeded is sometimes
534 // printed.
535 print_gc_overhead_limit_would_be_exceeded = true;
536
537 } else {
538 // Did not exceed overhead limits
539 reset_gc_overhead_limit_count();
540 }
541 }
542
543 if (UseGCOverheadLimit && PrintGCDetails && Verbose) {
544 if (gc_overhead_limit_exceeded()) {
545 gclog_or_tty->print_cr(" GC is exceeding overhead limit "
546 "of " UINTX_FORMAT "%%", GCTimeLimit);
547 reset_gc_overhead_limit_count();
548 } else if (print_gc_overhead_limit_would_be_exceeded) {
549 assert(gc_overhead_limit_count() > 0, "Should not be printing");
550 gclog_or_tty->print_cr(" GC would exceed overhead limit "
551 "of " UINTX_FORMAT "%% %d consecutive time(s)",
552 GCTimeLimit, gc_overhead_limit_count());
553 }
554 }
555 }
556 // Printing
557
558 bool AdaptiveSizePolicy::print_adaptive_size_policy_on(outputStream* st) const {
559
560 // Should only be used with adaptive size policy turned on.
561 // Otherwise, there may be variables that are undefined.
562 if (!UseAdaptiveSizePolicy) return false;
563
564 // Print goal for which action is needed.
565 char* action = NULL;
566 bool change_for_pause = false;
567 if ((change_old_gen_for_maj_pauses() ==
568 decrease_old_gen_for_maj_pauses_true) ||
569 (change_young_gen_for_min_pauses() ==
570 decrease_young_gen_for_min_pauses_true)) {
571 action = (char*) " *** pause time goal ***";
572 change_for_pause = true;
573 } else if ((change_old_gen_for_throughput() ==
574 increase_old_gen_for_throughput_true) ||
575 (change_young_gen_for_throughput() ==
576 increase_young_gen_for_througput_true)) {
577 action = (char*) " *** throughput goal ***";
578 } else if (decrease_for_footprint()) {
579 action = (char*) " *** reduced footprint ***";
580 } else {
581 // No actions were taken. This can legitimately be the
582 // situation if not enough data has been gathered to make
610 if (change_old_gen_for_throughput() == increase_old_gen_for_throughput_true) {
611 assert(change_young_gen_for_throughput() ==
612 increase_young_gen_for_througput_true,
613 "Both generations should be growing");
614 young_gen_action = grow_msg;
615 tenured_gen_action = grow_msg;
616 } else if (change_young_gen_for_throughput() ==
617 increase_young_gen_for_througput_true) {
618 // Only the young generation may grow at start up (before
619 // enough full collections have been done to grow the old generation).
620 young_gen_action = grow_msg;
621 tenured_gen_action = no_change_msg;
622 }
623
624 // Minimum footprint
625 if (decrease_for_footprint() != 0) {
626 young_gen_action = shrink_msg;
627 tenured_gen_action = shrink_msg;
628 }
629
630 st->print_cr(" UseAdaptiveSizePolicy actions to meet %s", action);
631 st->print_cr(" GC overhead (%%)");
632 st->print_cr(" Young generation: %7.2f\t %s",
633 100.0 * avg_minor_gc_cost()->average(),
634 young_gen_action);
635 st->print_cr(" Tenured generation: %7.2f\t %s",
636 100.0 * avg_major_gc_cost()->average(),
637 tenured_gen_action);
638 return true;
639 }
640
641 bool AdaptiveSizePolicy::print_adaptive_size_policy_on(
642 outputStream* st,
643 uint tenuring_threshold_arg) const {
644 if (!AdaptiveSizePolicy::print_adaptive_size_policy_on(st)) {
645 return false;
646 }
647
648 // Tenuring threshold
649 bool tenuring_threshold_changed = true;
650 if (decrement_tenuring_threshold_for_survivor_limit()) {
651 st->print(" Tenuring threshold: (attempted to decrease to avoid"
652 " survivor space overflow) = ");
653 } else if (decrement_tenuring_threshold_for_gc_cost()) {
654 st->print(" Tenuring threshold: (attempted to decrease to balance"
655 " GC costs) = ");
656 } else if (increment_tenuring_threshold_for_gc_cost()) {
657 st->print(" Tenuring threshold: (attempted to increase to balance"
658 " GC costs) = ");
659 } else {
660 tenuring_threshold_changed = false;
661 assert(!tenuring_threshold_change(), "(no change was attempted)");
662 }
663 if (tenuring_threshold_changed) {
664 st->print_cr("%u", tenuring_threshold_arg);
665 }
666 return true;
667 }
|
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/shared/adaptiveSizePolicy.hpp"
27 #include "gc/shared/collectorPolicy.hpp"
28 #include "gc/shared/gcCause.hpp"
29 #include "gc/shared/workgroup.hpp"
30 #include "logging/log.hpp"
31 #include "runtime/timer.hpp"
32 #include "utilities/ostream.hpp"
33 elapsedTimer AdaptiveSizePolicy::_minor_timer;
34 elapsedTimer AdaptiveSizePolicy::_major_timer;
35 bool AdaptiveSizePolicy::_debug_perturbation = false;
36
37 // The throughput goal is implemented as
38 // _throughput_goal = 1 - ( 1 / (1 + gc_cost_ratio))
39 // gc_cost_ratio is the ratio
40 // application cost / gc cost
41 // For example a gc_cost_ratio of 4 translates into a
42 // throughput goal of .80
43
44 AdaptiveSizePolicy::AdaptiveSizePolicy(size_t init_eden_size,
45 size_t init_promo_size,
46 size_t init_survivor_size,
47 double gc_pause_goal_sec,
48 uint gc_cost_ratio) :
49 _eden_size(init_eden_size),
50 _promo_size(init_promo_size),
150 if (ForceDynamicNumberOfGCThreads) {
151 // Assume this is debugging and jiggle the number of GC threads.
152 if (new_active_workers == prev_active_workers) {
153 if (new_active_workers < total_workers) {
154 new_active_workers++;
155 } else if (new_active_workers > min_workers) {
156 new_active_workers--;
157 }
158 }
159 if (new_active_workers == total_workers) {
160 if (_debug_perturbation) {
161 new_active_workers = min_workers;
162 }
163 _debug_perturbation = !_debug_perturbation;
164 }
165 assert((new_active_workers <= ParallelGCThreads) &&
166 (new_active_workers >= min_workers),
167 "Jiggled active workers too much");
168 }
169
170 log_trace(gc, task)("GCTaskManager::calc_default_active_workers() : "
171 "active_workers(): " UINTX_FORMAT " new_active_workers: " UINTX_FORMAT " "
172 "prev_active_workers: " UINTX_FORMAT "\n"
173 " active_workers_by_JT: " UINTX_FORMAT " active_workers_by_heap_size: " UINTX_FORMAT,
174 active_workers, new_active_workers, prev_active_workers,
175 active_workers_by_JT, active_workers_by_heap_size);
176 assert(new_active_workers > 0, "Always need at least 1");
177 return new_active_workers;
178 }
179
180 uint AdaptiveSizePolicy::calc_active_workers(uintx total_workers,
181 uintx active_workers,
182 uintx application_workers) {
183 // If the user has specifically set the number of
184 // GC threads, use them.
185
186 // If the user has turned off using a dynamic number of GC threads
187 // or the users has requested a specific number, set the active
188 // number of workers to all the workers.
189
190 uint new_active_workers;
191 if (!UseDynamicNumberOfGCThreads ||
192 (!FLAG_IS_DEFAULT(ParallelGCThreads) && !ForceDynamicNumberOfGCThreads)) {
193 new_active_workers = total_workers;
194 } else {
195 uintx min_workers = (total_workers == 1) ? 1 : 2;
257 (minor_pause_in_seconds > 0.0)) {
258 double interval_in_seconds =
259 _latest_minor_mutator_interval_seconds + minor_pause_in_seconds;
260 collection_cost =
261 minor_pause_in_seconds / interval_in_seconds;
262 _avg_minor_gc_cost->sample(collection_cost);
263 // Sample for performance counter
264 _avg_minor_interval->sample(interval_in_seconds);
265 }
266
267 // The policy does not have enough data until at least some
268 // young collections have been done.
269 _young_gen_policy_is_ready =
270 (_avg_minor_gc_cost->count() >= AdaptiveSizePolicyReadyThreshold);
271
272 // Calculate variables used to estimate pause time vs. gen sizes
273 double eden_size_in_mbytes = ((double)_eden_size) / ((double)M);
274 update_minor_pause_young_estimator(minor_pause_in_ms);
275 update_minor_pause_old_estimator(minor_pause_in_ms);
276
277 log_trace(gc, ergo)("AdaptiveSizePolicy::minor_collection_end: minor gc cost: %f average: %f",
278 collection_cost, _avg_minor_gc_cost->average());
279 log_trace(gc, ergo)(" minor pause: %f minor period %f",
280 minor_pause_in_ms, _latest_minor_mutator_interval_seconds * MILLIUNITS);
281
282 // Calculate variable used to estimate collection cost vs. gen sizes
283 assert(collection_cost >= 0.0, "Expected to be non-negative");
284 _minor_collection_estimator->update(eden_size_in_mbytes, collection_cost);
285 }
286
287 // Interval times use this timer to measure the mutator time.
288 // Reset the timer after the GC pause.
289 _minor_timer.reset();
290 _minor_timer.start();
291 }
292
293 size_t AdaptiveSizePolicy::eden_increment(size_t cur_eden, uint percent_change) {
294 size_t eden_heap_delta;
295 eden_heap_delta = cur_eden / 100 * percent_change;
296 return eden_heap_delta;
297 }
298
299 size_t AdaptiveSizePolicy::eden_increment(size_t cur_eden) {
300 return eden_increment(cur_eden, YoungGenerationSizeIncrement);
366 // small. Use the decaying gc cost only to decide whether to
367 // adjust for throughput. Using it also to determine the adjustment
368 // to be made for throughput also seems reasonable but there is
369 // no test case to use to decide if it is the right thing to do
370 // don't do it yet.
371
372 double AdaptiveSizePolicy::decaying_gc_cost() const {
373 double decayed_major_gc_cost = major_gc_cost();
374 double avg_major_interval = major_gc_interval_average_for_decay();
375 if (UseAdaptiveSizeDecayMajorGCCost &&
376 (AdaptiveSizeMajorGCDecayTimeScale > 0) &&
377 (avg_major_interval > 0.00)) {
378 double time_since_last_major_gc = time_since_major_gc();
379
380 // Decay the major gc cost?
381 if (time_since_last_major_gc >
382 ((double) AdaptiveSizeMajorGCDecayTimeScale) * avg_major_interval) {
383
384 // Decay using the time-since-last-major-gc
385 decayed_major_gc_cost = decaying_major_gc_cost();
386 log_trace(gc, ergo)("decaying_gc_cost: major interval average: %f time since last major gc: %f",
387 avg_major_interval, time_since_last_major_gc);
388 log_trace(gc, ergo)(" major gc cost: %f decayed major gc cost: %f",
389 major_gc_cost(), decayed_major_gc_cost);
390 }
391 }
392 double result = MIN2(1.0, decayed_major_gc_cost + minor_gc_cost());
393 return result;
394 }
395
396
397 void AdaptiveSizePolicy::clear_generation_free_space_flags() {
398 set_change_young_gen_for_min_pauses(0);
399 set_change_old_gen_for_maj_pauses(0);
400
401 set_change_old_gen_for_throughput(0);
402 set_change_young_gen_for_throughput(0);
403 set_decrease_for_footprint(0);
404 set_decide_at_full_gc(0);
405 }
406
407 void AdaptiveSizePolicy::check_gc_overhead_limit(
408 size_t young_live,
409 size_t eden_live,
410 size_t max_old_gen_size,
411 size_t max_eden_size,
436 // space has suddenly jumped up). If the current is much
437 // higher than the average, use the average since it represents
438 // the longer term behavior.
439 const size_t live_in_eden =
440 MIN2(eden_live, (size_t) avg_eden_live()->average());
441 const size_t free_in_eden = max_eden_size > live_in_eden ?
442 max_eden_size - live_in_eden : 0;
443 const size_t free_in_old_gen = (size_t)(max_old_gen_size - avg_old_live()->average());
444 const size_t total_free_limit = free_in_old_gen + free_in_eden;
445 const size_t total_mem = max_old_gen_size + max_eden_size;
446 const double mem_free_limit = total_mem * (GCHeapFreeLimit/100.0);
447 const double mem_free_old_limit = max_old_gen_size * (GCHeapFreeLimit/100.0);
448 const double mem_free_eden_limit = max_eden_size * (GCHeapFreeLimit/100.0);
449 const double gc_cost_limit = GCTimeLimit/100.0;
450 size_t promo_limit = (size_t)(max_old_gen_size - avg_old_live()->average());
451 // But don't force a promo size below the current promo size. Otherwise,
452 // the promo size will shrink for no good reason.
453 promo_limit = MAX2(promo_limit, _promo_size);
454
455
456 log_trace(gc, ergo)(
457 "PSAdaptiveSizePolicy::check_gc_overhead_limit:"
458 " promo_limit: " SIZE_FORMAT
459 " max_eden_size: " SIZE_FORMAT
460 " total_free_limit: " SIZE_FORMAT
461 " max_old_gen_size: " SIZE_FORMAT
462 " max_eden_size: " SIZE_FORMAT
463 " mem_free_limit: " SIZE_FORMAT,
464 promo_limit, max_eden_size, total_free_limit,
465 max_old_gen_size, max_eden_size,
466 (size_t) mem_free_limit);
467
468 bool print_gc_overhead_limit_would_be_exceeded = false;
469 if (is_full_gc) {
470 if (gc_cost() > gc_cost_limit &&
471 free_in_old_gen < (size_t) mem_free_old_limit &&
472 free_in_eden < (size_t) mem_free_eden_limit) {
473 // Collections, on average, are taking too much time, and
474 // gc_cost() > gc_cost_limit
475 // we have too little space available after a full gc.
476 // total_free_limit < mem_free_limit
477 // where
478 // total_free_limit is the free space available in
479 // both generations
480 // total_mem is the total space available for allocation
481 // in both generations (survivor spaces are not included
482 // just as they are not included in eden_limit).
483 // mem_free_limit is a fraction of total_mem judged to be an
484 // acceptable amount that is still unused.
485 // The heap can ask for the value of this variable when deciding
486 // whether to thrown an OutOfMemory error.
492 // At this point the GC overhead limit is being exceeded.
493 inc_gc_overhead_limit_count();
494 if (UseGCOverheadLimit) {
495 if (gc_overhead_limit_count() >=
496 AdaptiveSizePolicyGCTimeLimitThreshold){
497 // All conditions have been met for throwing an out-of-memory
498 set_gc_overhead_limit_exceeded(true);
499 // Avoid consecutive OOM due to the gc time limit by resetting
500 // the counter.
501 reset_gc_overhead_limit_count();
502 } else {
503 // The required consecutive collections which exceed the
504 // GC time limit may or may not have been reached. We
505 // are approaching that condition and so as not to
506 // throw an out-of-memory before all SoftRef's have been
507 // cleared, set _should_clear_all_soft_refs in CollectorPolicy.
508 // The clearing will be done on the next GC.
509 bool near_limit = gc_overhead_limit_near();
510 if (near_limit) {
511 collector_policy->set_should_clear_all_soft_refs(true);
512 log_trace(gc, ergo)("Nearing GC overhead limit, will be clearing all SoftReference");
513 }
514 }
515 }
516 // Set this even when the overhead limit will not
517 // cause an out-of-memory. Diagnostic message indicating
518 // that the overhead limit is being exceeded is sometimes
519 // printed.
520 print_gc_overhead_limit_would_be_exceeded = true;
521
522 } else {
523 // Did not exceed overhead limits
524 reset_gc_overhead_limit_count();
525 }
526 }
527
528 if (UseGCOverheadLimit) {
529 if (gc_overhead_limit_exceeded()) {
530 log_trace(gc, ergo)("GC is exceeding overhead limit of " UINTX_FORMAT "%%", GCTimeLimit);
531 reset_gc_overhead_limit_count();
532 } else if (print_gc_overhead_limit_would_be_exceeded) {
533 assert(gc_overhead_limit_count() > 0, "Should not be printing");
534 log_trace(gc, ergo)("GC would exceed overhead limit of " UINTX_FORMAT "%% %d consecutive time(s)",
535 GCTimeLimit, gc_overhead_limit_count());
536 }
537 }
538 }
539 // Printing
540
541 bool AdaptiveSizePolicy::print() const {
542 assert(UseAdaptiveSizePolicy, "UseAdaptiveSizePolicy need to be enabled.");
543
544 if (!Log<LOG_TAGS(gc, ergo)>::is_debug()) {
545 return false;
546 }
547
548 // Print goal for which action is needed.
549 char* action = NULL;
550 bool change_for_pause = false;
551 if ((change_old_gen_for_maj_pauses() ==
552 decrease_old_gen_for_maj_pauses_true) ||
553 (change_young_gen_for_min_pauses() ==
554 decrease_young_gen_for_min_pauses_true)) {
555 action = (char*) " *** pause time goal ***";
556 change_for_pause = true;
557 } else if ((change_old_gen_for_throughput() ==
558 increase_old_gen_for_throughput_true) ||
559 (change_young_gen_for_throughput() ==
560 increase_young_gen_for_througput_true)) {
561 action = (char*) " *** throughput goal ***";
562 } else if (decrease_for_footprint()) {
563 action = (char*) " *** reduced footprint ***";
564 } else {
565 // No actions were taken. This can legitimately be the
566 // situation if not enough data has been gathered to make
594 if (change_old_gen_for_throughput() == increase_old_gen_for_throughput_true) {
595 assert(change_young_gen_for_throughput() ==
596 increase_young_gen_for_througput_true,
597 "Both generations should be growing");
598 young_gen_action = grow_msg;
599 tenured_gen_action = grow_msg;
600 } else if (change_young_gen_for_throughput() ==
601 increase_young_gen_for_througput_true) {
602 // Only the young generation may grow at start up (before
603 // enough full collections have been done to grow the old generation).
604 young_gen_action = grow_msg;
605 tenured_gen_action = no_change_msg;
606 }
607
608 // Minimum footprint
609 if (decrease_for_footprint() != 0) {
610 young_gen_action = shrink_msg;
611 tenured_gen_action = shrink_msg;
612 }
613
614 log_debug(gc, ergo)("UseAdaptiveSizePolicy actions to meet %s", action);
615 log_debug(gc, ergo)(" GC overhead (%%)");
616 log_debug(gc, ergo)(" Young generation: %7.2f\t %s",
617 100.0 * avg_minor_gc_cost()->average(), young_gen_action);
618 log_debug(gc, ergo)(" Tenured generation: %7.2f\t %s",
619 100.0 * avg_major_gc_cost()->average(), tenured_gen_action);
620 return true;
621 }
622
623 void AdaptiveSizePolicy::print_tenuring_threshold( uint new_tenuring_threshold_arg) const {
624 // Tenuring threshold
625 if (decrement_tenuring_threshold_for_survivor_limit()) {
626 log_debug(gc, ergo)("Tenuring threshold: (attempted to decrease to avoid survivor space overflow) = %u", new_tenuring_threshold_arg);
627 } else if (decrement_tenuring_threshold_for_gc_cost()) {
628 log_debug(gc, ergo)("Tenuring threshold: (attempted to decrease to balance GC costs) = %u", new_tenuring_threshold_arg);
629 } else if (increment_tenuring_threshold_for_gc_cost()) {
630 log_debug(gc, ergo)("Tenuring threshold: (attempted to increase to balance GC costs) = %u", new_tenuring_threshold_arg);
631 } else {
632 assert(!tenuring_threshold_change(), "(no change was attempted)");
633 }
634 }
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