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/g1/g1ErgoVerbose.hpp" 30 #include "gc/shared/space.inline.hpp" 31 #include "runtime/atomic.inline.hpp" 32 33 // Even though we don't use the GC efficiency in our heuristics as 34 // much as we used to, we still order according to GC efficiency. This 35 // will cause regions with a lot of live objects and large RSets to 36 // end up at the end of the array. Given that we might skip collecting 37 // the last few old regions, if after a few mixed GCs the remaining 38 // have reclaimable bytes under a certain threshold, the hope is that 39 // the ones we'll skip are ones with both large RSets and a lot of 40 // live objects, not the ones with just a lot of live objects if we 41 // ordered according to the amount of reclaimable bytes per region. 42 static int order_regions(HeapRegion* hr1, HeapRegion* hr2) { 43 if (hr1 == NULL) { 44 if (hr2 == NULL) { 45 return 0; 46 } else { 47 return 1; 48 } 49 } else if (hr2 == NULL) { 50 return -1; 51 } 52 53 double gc_eff1 = hr1->gc_efficiency(); 54 double gc_eff2 = hr2->gc_efficiency(); 55 if (gc_eff1 > gc_eff2) { 56 return -1; 57 } if (gc_eff1 < gc_eff2) { 58 return 1; 59 } else { 60 return 0; 61 } 62 } 63 64 static int order_regions(HeapRegion** hr1p, HeapRegion** hr2p) { 65 return order_regions(*hr1p, *hr2p); 66 } 67 68 CollectionSetChooser::CollectionSetChooser() : 69 // The line below is the worst bit of C++ hackery I've ever written 70 // (Detlefs, 11/23). You should think of it as equivalent to 71 // "_regions(100, true)": initialize the growable array and inform it 72 // that it should allocate its elem array(s) on the C heap. 73 // 74 // The first argument, however, is actually a comma expression 75 // (set_allocation_type(this, C_HEAP), 100). The purpose of the 76 // set_allocation_type() call is to replace the default allocation 77 // type for embedded objects STACK_OR_EMBEDDED with C_HEAP. It will 78 // allow to pass the assert in GenericGrowableArray() which checks 79 // that a growable array object must be on C heap if elements are. 80 // 81 // Note: containing object is allocated on C heap since it is CHeapObj. 82 // 83 _regions((ResourceObj::set_allocation_type((address) &_regions, 84 ResourceObj::C_HEAP), 85 100), true /* C_Heap */), 86 _curr_index(0), _length(0), _first_par_unreserved_idx(0), 87 _region_live_threshold_bytes(0), _remaining_reclaimable_bytes(0) { 88 _region_live_threshold_bytes = 89 HeapRegion::GrainBytes * (size_t) G1MixedGCLiveThresholdPercent / 100; 90 } 91 92 #ifndef PRODUCT 93 void CollectionSetChooser::verify() { 94 guarantee(_length <= regions_length(), 95 err_msg("_length: %u regions length: %u", _length, regions_length())); 96 guarantee(_curr_index <= _length, 97 err_msg("_curr_index: %u _length: %u", _curr_index, _length)); 98 uint index = 0; 99 size_t sum_of_reclaimable_bytes = 0; 100 while (index < _curr_index) { 101 guarantee(regions_at(index) == NULL, 102 "all entries before _curr_index should be NULL"); 103 index += 1; 104 } 105 HeapRegion *prev = NULL; 106 while (index < _length) { 107 HeapRegion *curr = regions_at(index++); 108 guarantee(curr != NULL, "Regions in _regions array cannot be NULL"); 109 guarantee(!curr->is_young(), "should not be young!"); 110 guarantee(!curr->is_humongous(), "should not be humongous!"); 111 if (prev != NULL) { 112 guarantee(order_regions(prev, curr) != 1, 113 err_msg("GC eff prev: %1.4f GC eff curr: %1.4f", 114 prev->gc_efficiency(), curr->gc_efficiency())); 115 } 116 sum_of_reclaimable_bytes += curr->reclaimable_bytes(); 117 prev = curr; 118 } 119 guarantee(sum_of_reclaimable_bytes == _remaining_reclaimable_bytes, 120 err_msg("reclaimable bytes inconsistent, " 121 "remaining: "SIZE_FORMAT" sum: "SIZE_FORMAT, 122 _remaining_reclaimable_bytes, sum_of_reclaimable_bytes)); 123 } 124 #endif // !PRODUCT 125 126 void CollectionSetChooser::sort_regions() { 127 // First trim any unused portion of the top in the parallel case. 128 if (_first_par_unreserved_idx > 0) { 129 assert(_first_par_unreserved_idx <= regions_length(), 130 "Or we didn't reserved enough length"); 131 regions_trunc_to(_first_par_unreserved_idx); 132 } 133 _regions.sort(order_regions); 134 assert(_length <= regions_length(), "Requirement"); 135 #ifdef ASSERT 136 for (uint i = 0; i < _length; i++) { 137 assert(regions_at(i) != NULL, "Should be true by sorting!"); 138 } 139 #endif // ASSERT 140 if (G1PrintRegionLivenessInfo) { 141 G1PrintRegionLivenessInfoClosure cl(gclog_or_tty, "Post-Sorting"); 142 for (uint i = 0; i < _length; ++i) { 143 HeapRegion* r = regions_at(i); 144 cl.doHeapRegion(r); 145 } 146 } 147 verify(); 148 } 149 150 151 void CollectionSetChooser::add_region(HeapRegion* hr) { 152 assert(!hr->is_humongous(), 153 "Humongous regions shouldn't be added to the collection set"); 154 assert(!hr->is_young(), "should not be young!"); 155 _regions.append(hr); 156 _length++; 157 _remaining_reclaimable_bytes += hr->reclaimable_bytes(); 158 hr->calc_gc_efficiency(); 159 } 160 161 void CollectionSetChooser::prepare_for_par_region_addition(uint n_regions, 162 uint chunk_size) { 163 _first_par_unreserved_idx = 0; 164 uint n_threads = (uint) ParallelGCThreads; 165 if (UseDynamicNumberOfGCThreads) { 166 assert(G1CollectedHeap::heap()->workers()->active_workers() > 0, 167 "Should have been set earlier"); 168 // This is defensive code. As the assertion above says, the number 169 // of active threads should be > 0, but in case there is some path 170 // or some improperly initialized variable with leads to no 171 // active threads, protect against that in a product build. 172 n_threads = MAX2(G1CollectedHeap::heap()->workers()->active_workers(), 173 1U); 174 } 175 uint max_waste = n_threads * chunk_size; 176 // it should be aligned with respect to chunk_size 177 uint aligned_n_regions = (n_regions + chunk_size - 1) / chunk_size * chunk_size; 178 assert(aligned_n_regions % chunk_size == 0, "should be aligned"); 179 regions_at_put_grow(aligned_n_regions + max_waste - 1, NULL); 180 } 181 182 uint CollectionSetChooser::claim_array_chunk(uint chunk_size) { 183 uint res = (uint) Atomic::add((jint) chunk_size, 184 (volatile jint*) &_first_par_unreserved_idx); 185 assert(regions_length() > res + chunk_size - 1, 186 "Should already have been expanded"); 187 return res - chunk_size; 188 } 189 190 void CollectionSetChooser::set_region(uint index, HeapRegion* hr) { 191 assert(regions_at(index) == NULL, "precondition"); 192 assert(!hr->is_young(), "should not be young!"); 193 regions_at_put(index, hr); 194 hr->calc_gc_efficiency(); 195 } 196 197 void CollectionSetChooser::update_totals(uint region_num, 198 size_t reclaimable_bytes) { 199 // Only take the lock if we actually need to update the totals. 200 if (region_num > 0) { 201 assert(reclaimable_bytes > 0, "invariant"); 202 // We could have just used atomics instead of taking the 203 // lock. However, we currently don't have an atomic add for size_t. 204 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag); 205 _length += region_num; 206 _remaining_reclaimable_bytes += reclaimable_bytes; 207 } else { 208 assert(reclaimable_bytes == 0, "invariant"); 209 } 210 } 211 212 void CollectionSetChooser::clear() { 213 _regions.clear(); 214 _curr_index = 0; 215 _length = 0; 216 _remaining_reclaimable_bytes = 0; 217 };