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src/hotspot/share/gc/shenandoah/shenandoahCollectionSet.cpp

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  1 /*
  2  * Copyright (c) 2016, 2023, Red Hat, Inc. 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 
 27 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
 28 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
 29 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
 30 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
 31 #include "gc/shenandoah/shenandoahUtils.hpp"
 32 #include "runtime/atomic.hpp"
 33 #include "services/memTracker.hpp"
 34 #include "utilities/copy.hpp"
 35 
 36 ShenandoahCollectionSet::ShenandoahCollectionSet(ShenandoahHeap* heap, ReservedSpace space, char* heap_base) :
 37   _map_size(heap->num_regions()),
 38   _region_size_bytes_shift(ShenandoahHeapRegion::region_size_bytes_shift()),
 39   _map_space(space),
 40   _cset_map(_map_space.base() + ((uintx)heap_base >> _region_size_bytes_shift)),
 41   _biased_cset_map(_map_space.base()),
 42   _heap(heap),

 43   _garbage(0),
 44   _used(0),

 45   _region_count(0),

 46   _current_index(0) {
 47 
 48   // The collection set map is reserved to cover the entire heap *and* zero addresses.
 49   // This is needed to accept in-cset checks for both heap oops and nulls, freeing
 50   // high-performance code from checking for null first.
 51   //
 52   // Since heap_base can be far away, committing the entire map would waste memory.
 53   // Therefore, we only commit the parts that are needed to operate: the heap view,
 54   // and the zero page.
 55   //
 56   // Note: we could instead commit the entire map, and piggyback on OS virtual memory
 57   // subsystem for mapping not-yet-written-to pages to a single physical backing page,
 58   // but this is not guaranteed, and would confuse NMT and other memory accounting tools.
 59 
 60   MemTracker::record_virtual_memory_type(_map_space.base(), mtGC);
 61 
 62   size_t page_size = os::vm_page_size();
 63 
 64   if (!_map_space.special()) {
 65     // Commit entire pages that cover the heap cset map.
 66     char* bot_addr = align_down(_cset_map, page_size);
 67     char* top_addr = align_up(_cset_map + _map_size, page_size);
 68     os::commit_memory_or_exit(bot_addr, pointer_delta(top_addr, bot_addr, 1), false,
 69                               "Unable to commit collection set bitmap: heap");
 70 
 71     // Commit the zero page, if not yet covered by heap cset map.
 72     if (bot_addr != _biased_cset_map) {
 73       os::commit_memory_or_exit(_biased_cset_map, page_size, false,
 74                                 "Unable to commit collection set bitmap: zero page");
 75     }
 76   }
 77 
 78   Copy::zero_to_bytes(_cset_map, _map_size);
 79   Copy::zero_to_bytes(_biased_cset_map, page_size);
 80 }
 81 
 82 void ShenandoahCollectionSet::add_region(ShenandoahHeapRegion* r) {
 83   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
 84   assert(Thread::current()->is_VM_thread(), "Must be VMThread");
 85   assert(!is_in(r), "Already in collection set");


 86   _cset_map[r->index()] = 1;

















 87   _region_count++;
 88   _garbage += r->garbage();

 89   _used += r->used();
 90 
 91   // Update the region status too. State transition would be checked internally.
 92   r->make_cset();
 93 }
 94 
 95 void ShenandoahCollectionSet::clear() {
 96   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");

 97   Copy::zero_to_bytes(_cset_map, _map_size);
 98 
 99 #ifdef ASSERT
100   for (size_t index = 0; index < _heap->num_regions(); index ++) {
101     assert (!_heap->get_region(index)->is_cset(), "should have been cleared before");
102   }
103 #endif
104 
105   _garbage = 0;

106   _used = 0;

107 
108   _region_count = 0;
109   _current_index = 0;












110 }
111 
112 ShenandoahHeapRegion* ShenandoahCollectionSet::claim_next() {
113   // This code is optimized for the case when collection set contains only
114   // a few regions. In this case, it is more constructive to check for is_in
115   // before hitting the (potentially contended) atomic index.
116 
117   size_t max = _heap->num_regions();
118   size_t old = Atomic::load(&_current_index);
119 
120   for (size_t index = old; index < max; index++) {
121     if (is_in(index)) {
122       size_t cur = Atomic::cmpxchg(&_current_index, old, index + 1, memory_order_relaxed);
123       assert(cur >= old, "Always move forward");
124       if (cur == old) {
125         // Successfully moved the claim index, this is our region.
126         return _heap->get_region(index);
127       } else {
128         // Somebody else moved the claim index, restart from there.
129         index = cur - 1; // adjust for loop post-increment

133   }
134   return nullptr;
135 }
136 
137 ShenandoahHeapRegion* ShenandoahCollectionSet::next() {
138   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
139   assert(Thread::current()->is_VM_thread(), "Must be VMThread");
140 
141   size_t max = _heap->num_regions();
142   for (size_t index = _current_index; index < max; index++) {
143     if (is_in(index)) {
144       _current_index = index + 1;
145       return _heap->get_region(index);
146     }
147   }
148 
149   return nullptr;
150 }
151 
152 void ShenandoahCollectionSet::print_on(outputStream* out) const {
153   out->print_cr("Collection Set : " SIZE_FORMAT "", count());




154 
155   debug_only(size_t regions = 0;)
156   for (size_t index = 0; index < _heap->num_regions(); index ++) {
157     if (is_in(index)) {
158       _heap->get_region(index)->print_on(out);
159       debug_only(regions ++;)
160     }
161   }
162   assert(regions == count(), "Must match");
163 }

  1 /*
  2  * Copyright (c) 2016, 2023, 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 
 28 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
 29 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
 30 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
 31 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
 32 #include "gc/shenandoah/shenandoahUtils.hpp"
 33 #include "runtime/atomic.hpp"
 34 #include "services/memTracker.hpp"
 35 #include "utilities/copy.hpp"
 36 
 37 ShenandoahCollectionSet::ShenandoahCollectionSet(ShenandoahHeap* heap, ReservedSpace space, char* heap_base) :
 38   _map_size(heap->num_regions()),
 39   _region_size_bytes_shift(ShenandoahHeapRegion::region_size_bytes_shift()),
 40   _map_space(space),
 41   _cset_map(_map_space.base() + ((uintx)heap_base >> _region_size_bytes_shift)),
 42   _biased_cset_map(_map_space.base()),
 43   _heap(heap),
 44   _has_old_regions(false),
 45   _garbage(0),
 46   _used(0),
 47   _live(0),
 48   _region_count(0),
 49   _old_garbage(0),
 50   _current_index(0) {
 51 
 52   // The collection set map is reserved to cover the entire heap *and* zero addresses.
 53   // This is needed to accept in-cset checks for both heap oops and nulls, freeing
 54   // high-performance code from checking for null first.
 55   //
 56   // Since heap_base can be far away, committing the entire map would waste memory.
 57   // Therefore, we only commit the parts that are needed to operate: the heap view,
 58   // and the zero page.
 59   //
 60   // Note: we could instead commit the entire map, and piggyback on OS virtual memory
 61   // subsystem for mapping not-yet-written-to pages to a single physical backing page,
 62   // but this is not guaranteed, and would confuse NMT and other memory accounting tools.
 63 
 64   MemTracker::record_virtual_memory_type(_map_space.base(), mtGC);
 65 
 66   size_t page_size = os::vm_page_size();
 67 
 68   if (!_map_space.special()) {
 69     // Commit entire pages that cover the heap cset map.
 70     char* bot_addr = align_down(_cset_map, page_size);
 71     char* top_addr = align_up(_cset_map + _map_size, page_size);
 72     os::commit_memory_or_exit(bot_addr, pointer_delta(top_addr, bot_addr, 1), false,
 73                               "Unable to commit collection set bitmap: heap");
 74 
 75     // Commit the zero page, if not yet covered by heap cset map.
 76     if (bot_addr != _biased_cset_map) {
 77       os::commit_memory_or_exit(_biased_cset_map, page_size, false,
 78                                 "Unable to commit collection set bitmap: zero page");
 79     }
 80   }
 81 
 82   Copy::zero_to_bytes(_cset_map, _map_size);
 83   Copy::zero_to_bytes(_biased_cset_map, page_size);
 84 }
 85 
 86 void ShenandoahCollectionSet::add_region(ShenandoahHeapRegion* r) {
 87   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
 88   assert(Thread::current()->is_VM_thread(), "Must be VMThread");
 89   assert(!is_in(r), "Already in collection set");
 90   assert(!r->is_humongous(), "Only add regular regions to the collection set");
 91 
 92   _cset_map[r->index()] = 1;
 93   size_t live    = r->get_live_data_bytes();
 94   size_t garbage = r->garbage();
 95   size_t free    = r->free();
 96   if (r->is_young()) {
 97     _young_region_count++;
 98     _young_bytes_to_evacuate += live;
 99     _young_available_bytes_collected += free;
100     if (ShenandoahHeap::heap()->mode()->is_generational() && r->age() >= ShenandoahHeap::heap()->age_census()->tenuring_threshold()) {
101       _young_bytes_to_promote += live;
102     }
103   } else if (r->is_old()) {
104     _old_region_count++;
105     _old_bytes_to_evacuate += live;
106     _old_garbage += garbage;
107     _old_available_bytes_collected += free;
108   }
109 
110   _region_count++;
111   _has_old_regions |= r->is_old();
112   _garbage += garbage;
113   _used += r->used();
114   _live += live;
115   // Update the region status too. State transition would be checked internally.
116   r->make_cset();
117 }
118 
119 void ShenandoahCollectionSet::clear() {
120   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
121 
122   Copy::zero_to_bytes(_cset_map, _map_size);
123 
124 #ifdef ASSERT
125   for (size_t index = 0; index < _heap->num_regions(); index ++) {
126     assert (!_heap->get_region(index)->is_cset(), "should have been cleared before");
127   }
128 #endif
129 
130   _garbage = 0;
131   _old_garbage = 0;
132   _used = 0;
133   _live = 0;
134 
135   _region_count = 0;
136   _current_index = 0;
137 
138   _young_region_count = 0;
139   _young_bytes_to_evacuate = 0;
140   _young_bytes_to_promote = 0;
141 
142   _old_region_count = 0;
143   _old_bytes_to_evacuate = 0;
144 
145   _young_available_bytes_collected = 0;
146   _old_available_bytes_collected = 0;
147 
148   _has_old_regions = false;
149 }
150 
151 ShenandoahHeapRegion* ShenandoahCollectionSet::claim_next() {
152   // This code is optimized for the case when collection set contains only
153   // a few regions. In this case, it is more constructive to check for is_in
154   // before hitting the (potentially contended) atomic index.
155 
156   size_t max = _heap->num_regions();
157   size_t old = Atomic::load(&_current_index);
158 
159   for (size_t index = old; index < max; index++) {
160     if (is_in(index)) {
161       size_t cur = Atomic::cmpxchg(&_current_index, old, index + 1, memory_order_relaxed);
162       assert(cur >= old, "Always move forward");
163       if (cur == old) {
164         // Successfully moved the claim index, this is our region.
165         return _heap->get_region(index);
166       } else {
167         // Somebody else moved the claim index, restart from there.
168         index = cur - 1; // adjust for loop post-increment

172   }
173   return nullptr;
174 }
175 
176 ShenandoahHeapRegion* ShenandoahCollectionSet::next() {
177   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
178   assert(Thread::current()->is_VM_thread(), "Must be VMThread");
179 
180   size_t max = _heap->num_regions();
181   for (size_t index = _current_index; index < max; index++) {
182     if (is_in(index)) {
183       _current_index = index + 1;
184       return _heap->get_region(index);
185     }
186   }
187 
188   return nullptr;
189 }
190 
191 void ShenandoahCollectionSet::print_on(outputStream* out) const {
192   out->print_cr("Collection Set: Regions: "
193                 SIZE_FORMAT ", Garbage: " SIZE_FORMAT "%s, Live: " SIZE_FORMAT "%s, Used: " SIZE_FORMAT "%s", count(),
194                 byte_size_in_proper_unit(garbage()), proper_unit_for_byte_size(garbage()),
195                 byte_size_in_proper_unit(live()),    proper_unit_for_byte_size(live()),
196                 byte_size_in_proper_unit(used()),    proper_unit_for_byte_size(used()));
197 
198   debug_only(size_t regions = 0;)
199   for (size_t index = 0; index < _heap->num_regions(); index ++) {
200     if (is_in(index)) {
201       _heap->get_region(index)->print_on(out);
202       debug_only(regions ++;)
203     }
204   }
205   assert(regions == count(), "Must match");
206 }
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