1 /*
2  * Copyright (c) 2016, 2018, Red Hat, Inc. All rights reserved.
3  *
4  * This code is free software; you can redistribute it and/or modify it
5  * under the terms of the GNU General Public License version 2 only, as
6  * published by the Free Software Foundation.
7  *
8  * This code is distributed in the hope that it will be useful, but WITHOUT
9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
11  * version 2 for more details (a copy is included in the LICENSE file that
12  * accompanied this code).
13  *
14  * You should have received a copy of the GNU General Public License version
15  * 2 along with this work; if not, write to the Free Software Foundation,
16  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
17  *
18  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
19  * or visit www.oracle.com if you need additional information or have any
20  * questions.
21  *
22  */
23 
24 #include "precompiled.hpp"
25 
26 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
27 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
28 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
29 #include "gc/shenandoah/shenandoahUtils.hpp"
30 #include "runtime/atomic.hpp"
31 #include "services/memTracker.hpp"
32 #include "utilities/copy.hpp"
33 
ShenandoahCollectionSet(ShenandoahHeap * heap,char * heap_base,size_t size)34 ShenandoahCollectionSet::ShenandoahCollectionSet(ShenandoahHeap* heap, char* heap_base, size_t size) :
35   _map_size(heap->num_regions()),
36   _region_size_bytes_shift(ShenandoahHeapRegion::region_size_bytes_shift()),
37   _map_space(align_up(((uintx)heap_base + size) >> _region_size_bytes_shift, os::vm_allocation_granularity())),
38   _cset_map(_map_space.base() + ((uintx)heap_base >> _region_size_bytes_shift)),
39   _biased_cset_map(_map_space.base()),
40   _heap(heap),
41   _garbage(0),
42   _live_data(0),
43   _used(0),
44   _region_count(0),
45   _current_index(0) {
46 
47   // The collection set map is reserved to cover the entire heap *and* zero addresses.
48   // This is needed to accept in-cset checks for both heap oops and NULLs, freeing
49   // high-performance code from checking for NULL first.
50   //
51   // Since heap_base can be far away, committing the entire map would waste memory.
52   // Therefore, we only commit the parts that are needed to operate: the heap view,
53   // and the zero page.
54   //
55   // Note: we could instead commit the entire map, and piggyback on OS virtual memory
56   // subsystem for mapping not-yet-written-to pages to a single physical backing page,
57   // but this is not guaranteed, and would confuse NMT and other memory accounting tools.
58 
59   MemTracker::record_virtual_memory_type(_map_space.base(), mtGC);
60 
61   size_t page_size = (size_t)os::vm_page_size();
62 
63   if (!_map_space.special()) {
64     // Commit entire pages that cover the heap cset map.
65     char* bot_addr = align_down(_cset_map, page_size);
66     char* top_addr = align_up(_cset_map + _map_size, page_size);
67     os::commit_memory_or_exit(bot_addr, pointer_delta(top_addr, bot_addr, 1), false,
68                               "Unable to commit collection set bitmap: heap");
69 
70     // Commit the zero page, if not yet covered by heap cset map.
71     if (bot_addr != _biased_cset_map) {
72       os::commit_memory_or_exit(_biased_cset_map, page_size, false,
73                                 "Unable to commit collection set bitmap: zero page");
74     }
75   }
76 
77   Copy::zero_to_bytes(_cset_map, _map_size);
78   Copy::zero_to_bytes(_biased_cset_map, page_size);
79 }
80 
add_region(ShenandoahHeapRegion * r)81 void ShenandoahCollectionSet::add_region(ShenandoahHeapRegion* r) {
82   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
83   assert(Thread::current()->is_VM_thread(), "Must be VMThread");
84   assert(!is_in(r), "Already in collection set");
85   _cset_map[r->region_number()] = 1;
86   _region_count ++;
87   _garbage += r->garbage();
88   _live_data += r->get_live_data_bytes();
89   _used += r->used();
90 }
91 
add_region_check_for_duplicates(ShenandoahHeapRegion * r)92 bool ShenandoahCollectionSet::add_region_check_for_duplicates(ShenandoahHeapRegion* r) {
93   if (!is_in(r)) {
94     add_region(r);
95     return true;
96   } else {
97     return false;
98   }
99 }
100 
remove_region(ShenandoahHeapRegion * r)101 void ShenandoahCollectionSet::remove_region(ShenandoahHeapRegion* r) {
102   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
103   assert(Thread::current()->is_VM_thread(), "Must be VMThread");
104   assert(is_in(r), "Not in collection set");
105   _cset_map[r->region_number()] = 0;
106   _region_count --;
107 }
108 
update_region_status()109 void ShenandoahCollectionSet::update_region_status() {
110   for (size_t index = 0; index < _heap->num_regions(); index ++) {
111     ShenandoahHeapRegion* r = _heap->get_region(index);
112     if (is_in(r)) {
113       r->make_cset();
114     } else {
115       assert (!r->is_cset(), "should not be cset");
116     }
117   }
118 }
119 
clear()120 void ShenandoahCollectionSet::clear() {
121   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
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   _live_data = 0;
132   _used = 0;
133 
134   _region_count = 0;
135   _current_index = 0;
136 }
137 
claim_next()138 ShenandoahHeapRegion* ShenandoahCollectionSet::claim_next() {
139   size_t num_regions = _heap->num_regions();
140   if (_current_index >= (jint)num_regions) {
141     return NULL;
142   }
143 
144   jint saved_current = _current_index;
145   size_t index = (size_t)saved_current;
146 
147   while(index < num_regions) {
148     if (is_in(index)) {
149       jint cur = Atomic::cmpxchg((jint)(index + 1), &_current_index, saved_current);
150       assert(cur >= (jint)saved_current, "Must move forward");
151       if (cur == saved_current) {
152         assert(is_in(index), "Invariant");
153         return _heap->get_region(index);
154       } else {
155         index = (size_t)cur;
156         saved_current = cur;
157       }
158     } else {
159       index ++;
160     }
161   }
162   return NULL;
163 }
164 
next()165 ShenandoahHeapRegion* ShenandoahCollectionSet::next() {
166   assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint");
167   assert(Thread::current()->is_VM_thread(), "Must be VMThread");
168   size_t num_regions = _heap->num_regions();
169   for (size_t index = (size_t)_current_index; index < num_regions; index ++) {
170     if (is_in(index)) {
171       _current_index = (jint)(index + 1);
172       return _heap->get_region(index);
173     }
174   }
175 
176   return NULL;
177 }
178 
print_on(outputStream * out) const179 void ShenandoahCollectionSet::print_on(outputStream* out) const {
180   out->print_cr("Collection Set : " SIZE_FORMAT "", count());
181 
182   debug_only(size_t regions = 0;)
183   for (size_t index = 0; index < _heap->num_regions(); index ++) {
184     if (is_in(index)) {
185       _heap->get_region(index)->print_on(out);
186       debug_only(regions ++;)
187     }
188   }
189   assert(regions == count(), "Must match");
190 }
191