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._u._garbage > b._u._garbage)
 40     return -1;
 41   else if (a._u._garbage < b._u._garbage)
 42     return 1;
 43   else return 0;
 44 }
 45 
 46 ShenandoahHeuristics::ShenandoahHeuristics(ShenandoahSpaceInfo* space_info) :
 47   _space_info(space_info),
 48   _region_data(nullptr),
 49   _guaranteed_gc_interval(0),

 50   _cycle_start(os::elapsedTime()),
 51   _last_cycle_end(0),
 52   _gc_times_learned(0),
 53   _gc_time_penalties(0),
 54   _gc_cycle_time_history(new TruncatedSeq(Moving_Average_Samples, ShenandoahAdaptiveDecayFactor)),
 55   _metaspace_oom()
 56 {
 57   size_t num_regions = ShenandoahHeap::heap()->num_regions();
 58   assert(num_regions > 0, "Sanity");
 59 
 60   _region_data = NEW_C_HEAP_ARRAY(RegionData, num_regions, mtGC);
 61 }
 62 
 63 ShenandoahHeuristics::~ShenandoahHeuristics() {
 64   FREE_C_HEAP_ARRAY(RegionGarbage, _region_data);
 65 }
 66 
 67 void ShenandoahHeuristics::choose_collection_set(ShenandoahCollectionSet* collection_set) {
 68   assert(collection_set->is_empty(), "Must be empty");
 69 
 70   ShenandoahHeap* heap = ShenandoahHeap::heap();
 71 
 72   // Check all pinned regions have updated status before choosing the collection set.
 73   heap->assert_pinned_region_status();
 74 
 75   // Step 1. Build up the region candidates we care about, rejecting losers and accepting winners right away.
 76 
 77   size_t num_regions = heap->num_regions();
 78 
 79   RegionData* candidates = _region_data;
 80 
 81   size_t cand_idx = 0;
 82 
 83   size_t total_garbage = 0;
 84 
 85   size_t immediate_garbage = 0;
 86   size_t immediate_regions = 0;
 87 
 88   size_t free = 0;
 89   size_t free_regions = 0;
 90 
 91   ShenandoahMarkingContext* const ctx = heap->complete_marking_context();
 92 
 93   for (size_t i = 0; i < num_regions; i++) {
 94     ShenandoahHeapRegion* region = heap->get_region(i);
 95 
 96     size_t garbage = region->garbage();
 97     total_garbage += garbage;
 98 
 99     if (region->is_empty()) {
100       free_regions++;
101       free += ShenandoahHeapRegion::region_size_bytes();
102     } else if (region->is_regular()) {
103       if (!region->has_live()) {
104         // We can recycle it right away and put it in the free set.
105         immediate_regions++;
106         immediate_garbage += garbage;
107         region->make_trash_immediate();
108       } else {
109         // This is our candidate for later consideration.
110         candidates[cand_idx]._region = region;
111         candidates[cand_idx]._u._garbage = garbage;
112         cand_idx++;
113       }
114     } else if (region->is_humongous_start()) {
115       // Reclaim humongous regions here, and count them as the immediate garbage
116 #ifdef ASSERT
117       bool reg_live = region->has_live();
118       bool bm_live = ctx->is_marked(cast_to_oop(region->bottom()));
119       assert(reg_live == bm_live,
120              "Humongous liveness and marks should agree. Region live: %s; Bitmap live: %s; Region Live Words: " SIZE_FORMAT,
121              BOOL_TO_STR(reg_live), BOOL_TO_STR(bm_live), region->get_live_data_words());
122 #endif
123       if (!region->has_live()) {
124         heap->trash_humongous_region_at(region);
125 
126         // Count only the start. Continuations would be counted on "trash" path
127         immediate_regions++;
128         immediate_garbage += garbage;
129       }
130     } else if (region->is_trash()) {
131       // Count in just trashed collection set, during coalesced CM-with-UR
132       immediate_regions++;
133       immediate_garbage += garbage;
134     }
135   }
136 
137   // Step 2. Look back at garbage statistics, and decide if we want to collect anything,
138   // given the amount of immediately reclaimable garbage. If we do, figure out the collection set.
139 
140   assert (immediate_garbage <= total_garbage,
141           "Cannot have more immediate garbage than total garbage: " SIZE_FORMAT "%s vs " SIZE_FORMAT "%s",
142           byte_size_in_proper_unit(immediate_garbage), proper_unit_for_byte_size(immediate_garbage),
143           byte_size_in_proper_unit(total_garbage),     proper_unit_for_byte_size(total_garbage));
144 
145   size_t immediate_percent = (total_garbage == 0) ? 0 : (immediate_garbage * 100 / total_garbage);
146 
147   if (immediate_percent <= ShenandoahImmediateThreshold) {
148     choose_collection_set_from_regiondata(collection_set, candidates, cand_idx, immediate_garbage + free);
149   }
150 
151   size_t cset_percent = (total_garbage == 0) ? 0 : (collection_set->garbage() * 100 / total_garbage);

152   size_t collectable_garbage = collection_set->garbage() + immediate_garbage;
153   size_t collectable_garbage_percent = (total_garbage == 0) ? 0 : (collectable_garbage * 100 / total_garbage);
154 
155   log_info(gc, ergo)("Collectable Garbage: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), "
156                      "Immediate: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), " SIZE_FORMAT " regions, "
157                      "CSet: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), " SIZE_FORMAT " regions",
158 
159                      byte_size_in_proper_unit(collectable_garbage),
160                      proper_unit_for_byte_size(collectable_garbage),
161                      collectable_garbage_percent,
162 
163                      byte_size_in_proper_unit(immediate_garbage),
164                      proper_unit_for_byte_size(immediate_garbage),
165                      immediate_percent,
166                      immediate_regions,
167 
168                      byte_size_in_proper_unit(collection_set->garbage()),
169                      proper_unit_for_byte_size(collection_set->garbage()),
170                      cset_percent,
171                      collection_set->count());
172 }
173 
174 void ShenandoahHeuristics::record_cycle_start() {
175   _cycle_start = os::elapsedTime();
176 }
177 
178 void ShenandoahHeuristics::record_cycle_end() {
179   _last_cycle_end = os::elapsedTime();
180 }
181 
182 bool ShenandoahHeuristics::should_start_gc() {
183   // Perform GC to cleanup metaspace
184   if (has_metaspace_oom()) {
185     // Some of vmTestbase/metaspace tests depend on following line to count GC cycles
186     log_info(gc)("Trigger: %s", GCCause::to_string(GCCause::_metadata_GC_threshold));
187     return true;
188   }
189 
190   if (_guaranteed_gc_interval > 0) {
191     double last_time_ms = (os::elapsedTime() - _last_cycle_end) * 1000;
192     if (last_time_ms > _guaranteed_gc_interval) {
193       log_info(gc)("Trigger (%s): Time since last GC (%.0f ms) is larger than guaranteed interval (" UINTX_FORMAT " ms)",
194                    _space_info->name(), last_time_ms, _guaranteed_gc_interval);
195       return true;
196     }
197   }
198 
199   return false;
200 }
201 
202 bool ShenandoahHeuristics::should_degenerate_cycle() {
203   return ShenandoahHeap::heap()->shenandoah_policy()->consecutive_degenerated_gc_count() <= ShenandoahFullGCThreshold;
204 }
205 
206 void ShenandoahHeuristics::adjust_penalty(intx step) {
207   assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
208          "In range before adjustment: " INTX_FORMAT, _gc_time_penalties);
209 
210   intx new_val = _gc_time_penalties + step;
211   if (new_val < 0) {
212     new_val = 0;
213   }
214   if (new_val > 100) {
215     new_val = 100;
216   }
217   _gc_time_penalties = new_val;
218 
219   assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
220          "In range after adjustment: " INTX_FORMAT, _gc_time_penalties);
221 }
222 
223 void ShenandoahHeuristics::record_success_concurrent(bool abbreviated) {




224   _gc_times_learned++;
225 
226   adjust_penalty(Concurrent_Adjust);
227 
228   if (_gc_times_learned <= ShenandoahLearningSteps || !(abbreviated && ShenandoahAdaptiveIgnoreShortCycles)) {
229     _gc_cycle_time_history->add(elapsed_cycle_time());
230   }
231 }
232 
233 void ShenandoahHeuristics::record_success_degenerated() {



234   adjust_penalty(Degenerated_Penalty);
235 }
236 
237 void ShenandoahHeuristics::record_success_full() {



238   adjust_penalty(Full_Penalty);
239 }
240 
241 void ShenandoahHeuristics::record_allocation_failure_gc() {
242   // Do nothing.
243 }
244 
245 void ShenandoahHeuristics::record_requested_gc() {
246   // Assume users call System.gc() when external state changes significantly,
247   // which forces us to re-learn the GC timings and allocation rates.
248   _gc_times_learned = 0;
249 }
250 
251 bool ShenandoahHeuristics::can_unload_classes() {
252   return ClassUnloading;

253 }
254 
255 bool ShenandoahHeuristics::should_unload_classes() {
256   if (!can_unload_classes()) return false;
257   if (has_metaspace_oom()) return true;
258   return ClassUnloadingWithConcurrentMark;
259 }
260 
261 void ShenandoahHeuristics::initialize() {
262   // Nothing to do by default.
263 }
264 
265 double ShenandoahHeuristics::elapsed_cycle_time() const {
266   return os::elapsedTime() - _cycle_start;
267 }
--- EOF ---