1 /*
  2  * Copyright (c) 2018, 2020, Red Hat, Inc. All rights reserved.
  3  * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
  4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  5  *
  6  * This code is free software; you can redistribute it and/or modify it
  7  * under the terms of the GNU General Public License version 2 only, as
  8  * published by the Free Software Foundation.
  9  *
 10  * This code is distributed in the hope that it will be useful, but WITHOUT
 11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 13  * version 2 for more details (a copy is included in the LICENSE file that
 14  * accompanied this code).
 15  *
 16  * You should have received a copy of the GNU General Public License version
 17  * 2 along with this work; if not, write to the Free Software Foundation,
 18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 19  *
 20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 21  * or visit www.oracle.com if you need additional information or have any
 22  * questions.
 23  *
 24  */
 25 
 26 #include "precompiled.hpp"
 27 #include "gc/shared/gcCause.hpp"
 28 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
 29 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
 30 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
 31 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
 32 #include "logging/log.hpp"
 33 #include "logging/logTag.hpp"
 34 #include "runtime/globals_extension.hpp"
 35 #include "utilities/quickSort.hpp"
 36 
 37 // sort by decreasing garbage (so most garbage comes first)
 38 int ShenandoahHeuristics::compare_by_garbage(RegionData a, RegionData b) {
 39   if (a.get_garbage() > b.get_garbage()) {
 40     return -1;
 41   } else if (a.get_garbage() < b.get_garbage()) {
 42     return 1;
 43   } else {
 44     return 0;
 45   }
 46 }
 47 
 48 ShenandoahHeuristics::ShenandoahHeuristics(ShenandoahSpaceInfo* space_info) :
 49   _space_info(space_info),
 50   _region_data(nullptr),
 51   _guaranteed_gc_interval(0),
 52   _cycle_start(os::elapsedTime()),
 53   _last_cycle_end(0),
 54   _gc_times_learned(0),
 55   _gc_time_penalties(0),
 56   _gc_cycle_time_history(new TruncatedSeq(Moving_Average_Samples, ShenandoahAdaptiveDecayFactor)),
 57   _metaspace_oom()
 58 {
 59   size_t num_regions = ShenandoahHeap::heap()->num_regions();
 60   assert(num_regions > 0, "Sanity");
 61 
 62   _region_data = NEW_C_HEAP_ARRAY(RegionData, num_regions, mtGC);
 63 #ifdef ASSERT
 64   for (size_t i = 0; i < num_regions; i++) {
 65     _region_data[i].clear();
 66   }
 67 #endif
 68 }
 69 
 70 ShenandoahHeuristics::~ShenandoahHeuristics() {
 71   FREE_C_HEAP_ARRAY(RegionGarbage, _region_data);
 72 }
 73 
 74 void ShenandoahHeuristics::choose_collection_set(ShenandoahCollectionSet* collection_set) {
 75   assert(collection_set->is_empty(), "Must be empty");
 76 
 77   ShenandoahHeap* heap = ShenandoahHeap::heap();
 78 
 79   // Check all pinned regions have updated status before choosing the collection set.
 80   heap->assert_pinned_region_status();
 81 
 82   // Step 1. Build up the region candidates we care about, rejecting losers and accepting winners right away.
 83 
 84   size_t num_regions = heap->num_regions();
 85 
 86   RegionData* candidates = _region_data;
 87 
 88   size_t cand_idx = 0;
 89 
 90   size_t total_garbage = 0;
 91 
 92   size_t immediate_garbage = 0;
 93   size_t immediate_regions = 0;
 94 
 95   size_t free = 0;
 96   size_t free_regions = 0;
 97 
 98   ShenandoahMarkingContext* const ctx = heap->complete_marking_context();
 99 
100   for (size_t i = 0; i < num_regions; i++) {
101     ShenandoahHeapRegion* region = heap->get_region(i);
102 
103     size_t garbage = region->garbage();
104     total_garbage += garbage;
105 
106     if (region->is_empty()) {
107       free_regions++;
108       free += ShenandoahHeapRegion::region_size_bytes();
109     } else if (region->is_regular()) {
110       if (!region->has_live()) {
111         // We can recycle it right away and put it in the free set.
112         immediate_regions++;
113         immediate_garbage += garbage;
114         region->make_trash_immediate();
115       } else {
116         // This is our candidate for later consideration.
117         candidates[cand_idx].set_region_and_garbage(region, garbage);
118         cand_idx++;
119       }
120     } else if (region->is_humongous_start()) {
121       // Reclaim humongous regions here, and count them as the immediate garbage
122 #ifdef ASSERT
123       bool reg_live = region->has_live();
124       bool bm_live = ctx->is_marked(cast_to_oop(region->bottom()));
125       assert(reg_live == bm_live,
126              "Humongous liveness and marks should agree. Region live: %s; Bitmap live: %s; Region Live Words: " SIZE_FORMAT,
127              BOOL_TO_STR(reg_live), BOOL_TO_STR(bm_live), region->get_live_data_words());
128 #endif
129       if (!region->has_live()) {
130         heap->trash_humongous_region_at(region);
131 
132         // Count only the start. Continuations would be counted on "trash" path
133         immediate_regions++;
134         immediate_garbage += garbage;
135       }
136     } else if (region->is_trash()) {
137       // Count in just trashed collection set, during coalesced CM-with-UR
138       immediate_regions++;
139       immediate_garbage += garbage;
140     }
141   }
142 
143   // Step 2. Look back at garbage statistics, and decide if we want to collect anything,
144   // given the amount of immediately reclaimable garbage. If we do, figure out the collection set.
145 
146   assert (immediate_garbage <= total_garbage,
147           "Cannot have more immediate garbage than total garbage: " SIZE_FORMAT "%s vs " SIZE_FORMAT "%s",
148           byte_size_in_proper_unit(immediate_garbage), proper_unit_for_byte_size(immediate_garbage),
149           byte_size_in_proper_unit(total_garbage),     proper_unit_for_byte_size(total_garbage));
150 
151   size_t immediate_percent = (total_garbage == 0) ? 0 : (immediate_garbage * 100 / total_garbage);
152 
153   if (immediate_percent <= ShenandoahImmediateThreshold) {
154     choose_collection_set_from_regiondata(collection_set, candidates, cand_idx, immediate_garbage + free);
155   }
156 
157   size_t cset_percent = (total_garbage == 0) ? 0 : (collection_set->garbage() * 100 / total_garbage);
158   size_t collectable_garbage = collection_set->garbage() + immediate_garbage;
159   size_t collectable_garbage_percent = (total_garbage == 0) ? 0 : (collectable_garbage * 100 / total_garbage);
160 
161   log_info(gc, ergo)("Collectable Garbage: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), "
162                      "Immediate: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), " SIZE_FORMAT " regions, "
163                      "CSet: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), " SIZE_FORMAT " regions",
164 
165                      byte_size_in_proper_unit(collectable_garbage),
166                      proper_unit_for_byte_size(collectable_garbage),
167                      collectable_garbage_percent,
168 
169                      byte_size_in_proper_unit(immediate_garbage),
170                      proper_unit_for_byte_size(immediate_garbage),
171                      immediate_percent,
172                      immediate_regions,
173 
174                      byte_size_in_proper_unit(collection_set->garbage()),
175                      proper_unit_for_byte_size(collection_set->garbage()),
176                      cset_percent,
177                      collection_set->count());
178 }
179 
180 void ShenandoahHeuristics::record_cycle_start() {
181   _cycle_start = os::elapsedTime();
182 }
183 
184 void ShenandoahHeuristics::record_cycle_end() {
185   _last_cycle_end = os::elapsedTime();
186 }
187 
188 bool ShenandoahHeuristics::should_start_gc() {
189   // Perform GC to cleanup metaspace
190   if (has_metaspace_oom()) {
191     // Some of vmTestbase/metaspace tests depend on following line to count GC cycles
192     log_info(gc)("Trigger: %s", GCCause::to_string(GCCause::_metadata_GC_threshold));
193     return true;
194   }
195 
196   if (_guaranteed_gc_interval > 0) {
197     double last_time_ms = (os::elapsedTime() - _last_cycle_end) * 1000;
198     if (last_time_ms > _guaranteed_gc_interval) {
199       log_info(gc)("Trigger (%s): Time since last GC (%.0f ms) is larger than guaranteed interval (" UINTX_FORMAT " ms)",
200                    _space_info->name(), last_time_ms, _guaranteed_gc_interval);
201       return true;
202     }
203   }
204 
205   return false;
206 }
207 
208 bool ShenandoahHeuristics::should_degenerate_cycle() {
209   return ShenandoahHeap::heap()->shenandoah_policy()->consecutive_degenerated_gc_count() <= ShenandoahFullGCThreshold;
210 }
211 
212 void ShenandoahHeuristics::adjust_penalty(intx step) {
213   assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
214          "In range before adjustment: " INTX_FORMAT, _gc_time_penalties);
215 
216   intx new_val = _gc_time_penalties + step;
217   if (new_val < 0) {
218     new_val = 0;
219   }
220   if (new_val > 100) {
221     new_val = 100;
222   }
223   _gc_time_penalties = new_val;
224 
225   assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
226          "In range after adjustment: " INTX_FORMAT, _gc_time_penalties);
227 }
228 
229 void ShenandoahHeuristics::record_success_concurrent() {
230   _gc_cycle_time_history->add(elapsed_cycle_time());
231   _gc_times_learned++;
232 
233   adjust_penalty(Concurrent_Adjust);
234 }
235 
236 void ShenandoahHeuristics::record_success_degenerated() {
237   adjust_penalty(Degenerated_Penalty);
238 }
239 
240 void ShenandoahHeuristics::record_success_full() {
241   adjust_penalty(Full_Penalty);
242 }
243 
244 void ShenandoahHeuristics::record_allocation_failure_gc() {
245   // Do nothing.
246 }
247 
248 void ShenandoahHeuristics::record_requested_gc() {
249   // Assume users call System.gc() when external state changes significantly,
250   // which forces us to re-learn the GC timings and allocation rates.
251   _gc_times_learned = 0;
252 }
253 
254 bool ShenandoahHeuristics::can_unload_classes() {
255   return ClassUnloading;
256 }
257 
258 bool ShenandoahHeuristics::should_unload_classes() {
259   if (!can_unload_classes()) return false;
260   if (has_metaspace_oom()) return true;
261   return ClassUnloadingWithConcurrentMark;
262 }
263 
264 void ShenandoahHeuristics::initialize() {
265   // Nothing to do by default.
266 }
267 
268 double ShenandoahHeuristics::elapsed_cycle_time() const {
269   return os::elapsedTime() - _cycle_start;
270 }