1 /* 2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. 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 #include "gc/g1/collectionSetChooser.hpp" 27 #include "gc/g1/g1CollectedHeap.inline.hpp" 28 #include "gc/g1/g1CollectorPolicy.hpp" 29 #include "gc/shared/space.inline.hpp" 30 #include "runtime/atomic.inline.hpp" 31 32 // Even though we don't use the GC efficiency in our heuristics as 33 // much as we used to, we still order according to GC efficiency. This 34 // will cause regions with a lot of live objects and large RSets to 35 // end up at the end of the array. Given that we might skip collecting 36 // the last few old regions, if after a few mixed GCs the remaining 37 // have reclaimable bytes under a certain threshold, the hope is that 38 // the ones we'll skip are ones with both large RSets and a lot of 39 // live objects, not the ones with just a lot of live objects if we 40 // ordered according to the amount of reclaimable bytes per region. 41 static int order_regions(HeapRegion* hr1, HeapRegion* hr2) { 42 if (hr1 == NULL) { 43 if (hr2 == NULL) { 44 return 0; 45 } else { 46 return 1; 47 } 48 } else if (hr2 == NULL) { 49 return -1; 50 } 51 52 double gc_eff1 = hr1->gc_efficiency(); 53 double gc_eff2 = hr2->gc_efficiency(); 54 if (gc_eff1 > gc_eff2) { 55 return -1; 56 } if (gc_eff1 < gc_eff2) { 57 return 1; 58 } else { 59 return 0; 60 } 61 } 62 63 static int order_regions(HeapRegion** hr1p, HeapRegion** hr2p) { 64 return order_regions(*hr1p, *hr2p); 65 } 66 67 CollectionSetChooser::CollectionSetChooser() : 68 // The line below is the worst bit of C++ hackery I've ever written 69 // (Detlefs, 11/23). You should think of it as equivalent to 70 // "_regions(100, true)": initialize the growable array and inform it 71 // that it should allocate its elem array(s) on the C heap. 72 // 73 // The first argument, however, is actually a comma expression 74 // (set_allocation_type(this, C_HEAP), 100). The purpose of the 75 // set_allocation_type() call is to replace the default allocation 76 // type for embedded objects STACK_OR_EMBEDDED with C_HEAP. It will 77 // allow to pass the assert in GenericGrowableArray() which checks 78 // that a growable array object must be on C heap if elements are. 79 // 80 // Note: containing object is allocated on C heap since it is CHeapObj. 81 // 82 _regions((ResourceObj::set_allocation_type((address) &_regions, 83 ResourceObj::C_HEAP), 84 100), true /* C_Heap */), 85 _front(0), _end(0), _first_par_unreserved_idx(0), 86 _region_live_threshold_bytes(0), _remaining_reclaimable_bytes(0) { 87 _region_live_threshold_bytes = 88 HeapRegion::GrainBytes * (size_t) G1MixedGCLiveThresholdPercent / 100; 89 } 90 91 #ifndef PRODUCT 92 void CollectionSetChooser::verify() { 93 guarantee(_end <= regions_length(), "_end: %u regions length: %u", _end, regions_length()); 94 guarantee(_front <= _end, "_front: %u _end: %u", _front, _end); 95 uint index = 0; 96 size_t sum_of_reclaimable_bytes = 0; 97 while (index < _front) { 98 guarantee(regions_at(index) == NULL, 99 "all entries before _front should be NULL"); 100 index += 1; 101 } 102 HeapRegion *prev = NULL; 103 while (index < _end) { 104 HeapRegion *curr = regions_at(index++); 105 guarantee(curr != NULL, "Regions in _regions array cannot be NULL"); 106 guarantee(!curr->is_young(), "should not be young!"); 107 guarantee(!curr->is_pinned(), 108 "Pinned region should not be in collection set (index %u)", curr->hrm_index()); 109 if (prev != NULL) { 110 guarantee(order_regions(prev, curr) != 1, 111 "GC eff prev: %1.4f GC eff curr: %1.4f", 112 prev->gc_efficiency(), curr->gc_efficiency()); 113 } 114 sum_of_reclaimable_bytes += curr->reclaimable_bytes(); 115 prev = curr; 116 } 117 guarantee(sum_of_reclaimable_bytes == _remaining_reclaimable_bytes, 118 "reclaimable bytes inconsistent, " 119 "remaining: " SIZE_FORMAT " sum: " SIZE_FORMAT, 120 _remaining_reclaimable_bytes, sum_of_reclaimable_bytes); 121 } 122 #endif // !PRODUCT 123 124 void CollectionSetChooser::sort_regions() { 125 // First trim any unused portion of the top in the parallel case. 126 if (_first_par_unreserved_idx > 0) { 127 assert(_first_par_unreserved_idx <= regions_length(), 128 "Or we didn't reserved enough length"); 129 regions_trunc_to(_first_par_unreserved_idx); 130 } 131 _regions.sort(order_regions); 132 assert(_end <= regions_length(), "Requirement"); 133 #ifdef ASSERT 134 for (uint i = 0; i < _end; i++) { 135 assert(regions_at(i) != NULL, "Should be true by sorting!"); 136 } 137 #endif // ASSERT 138 if (Log<LOG_TAGS(gc, liveness)>::is_trace()) { 139 G1PrintRegionLivenessInfoClosure cl("Post-Sorting"); 140 for (uint i = 0; i < _end; ++i) { 141 HeapRegion* r = regions_at(i); 142 cl.doHeapRegion(r); 143 } 144 } 145 verify(); 146 } 147 148 149 void CollectionSetChooser::add_region(HeapRegion* hr) { 150 assert(!hr->is_pinned(), 151 "Pinned region shouldn't be added to the collection set (index %u)", hr->hrm_index()); 152 assert(!hr->is_young(), "should not be young!"); 153 _regions.append(hr); 154 _end++; 155 _remaining_reclaimable_bytes += hr->reclaimable_bytes(); 156 hr->calc_gc_efficiency(); 157 } 158 159 void CollectionSetChooser::push(HeapRegion* hr) { 160 assert(hr != NULL, "Can't put back a NULL region"); 161 assert(_front >= 1, "Too many regions have been put back"); 162 _front--; 163 regions_at_put(_front, hr); 164 _remaining_reclaimable_bytes += hr->reclaimable_bytes(); 165 } 166 167 void CollectionSetChooser::prepare_for_par_region_addition(uint n_threads, 168 uint n_regions, 169 uint chunk_size) { 170 _first_par_unreserved_idx = 0; 171 uint max_waste = n_threads * chunk_size; 172 // it should be aligned with respect to chunk_size 173 uint aligned_n_regions = (n_regions + chunk_size - 1) / chunk_size * chunk_size; 174 assert(aligned_n_regions % chunk_size == 0, "should be aligned"); 175 regions_at_put_grow(aligned_n_regions + max_waste - 1, NULL); 176 } 177 178 uint CollectionSetChooser::claim_array_chunk(uint chunk_size) { 179 uint res = (uint) Atomic::add((jint) chunk_size, 180 (volatile jint*) &_first_par_unreserved_idx); 181 assert(regions_length() > res + chunk_size - 1, 182 "Should already have been expanded"); 183 return res - chunk_size; 184 } 185 186 void CollectionSetChooser::set_region(uint index, HeapRegion* hr) { 187 assert(regions_at(index) == NULL, "precondition"); 188 assert(!hr->is_young(), "should not be young!"); 189 regions_at_put(index, hr); 190 hr->calc_gc_efficiency(); 191 } 192 193 void CollectionSetChooser::update_totals(uint region_num, 194 size_t reclaimable_bytes) { 195 // Only take the lock if we actually need to update the totals. 196 if (region_num > 0) { 197 assert(reclaimable_bytes > 0, "invariant"); 198 // We could have just used atomics instead of taking the 199 // lock. However, we currently don't have an atomic add for size_t. 200 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 201 _end += region_num; 202 _remaining_reclaimable_bytes += reclaimable_bytes; 203 } else { 204 assert(reclaimable_bytes == 0, "invariant"); 205 } 206 } 207 208 void CollectionSetChooser::clear() { 209 _regions.clear(); 210 _front = 0; 211 _end = 0; 212 _remaining_reclaimable_bytes = 0; 213 };