1 /* 2 * Copyright (c) 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/heuristics/shenandoahPassiveHeuristics.hpp" 27 #include "gc/shenandoah/shenandoahCollectionSet.hpp" 28 #include "gc/shenandoah/shenandoahHeapRegion.hpp" 29 #include "logging/log.hpp" 30 #include "logging/logTag.hpp" 31 32 ShenandoahPassiveHeuristics::ShenandoahPassiveHeuristics() : ShenandoahHeuristics() { 33 // Do not allow concurrent cycles. 34 FLAG_SET_DEFAULT(ExplicitGCInvokesConcurrent, false); 35 FLAG_SET_DEFAULT(ShenandoahImplicitGCInvokesConcurrent, false); 36 37 // Passive runs with max speed, reacts on allocation failure. 38 FLAG_SET_DEFAULT(ShenandoahPacing, false); 39 40 // No need for evacuation reserve with Full GC, only for Degenerated GC. 41 if (!ShenandoahDegeneratedGC) { 42 SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahEvacReserve, 0); 43 } 44 45 // Disable known barriers by default. 46 SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahLoadRefBarrier); 47 SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahSATBBarrier); 48 SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahKeepAliveBarrier); 49 SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahStoreValEnqueueBarrier); 50 SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahCASBarrier); 51 SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahCloneBarrier); 52 53 // Final configuration checks 54 // No barriers are required to run. 55 } 56 57 bool ShenandoahPassiveHeuristics::should_start_normal_gc() const { 58 // Never do concurrent GCs. 59 return false; 60 } 61 62 bool ShenandoahPassiveHeuristics::should_process_references() { 63 // Always process references, if we can. 64 return can_process_references(); 65 } 66 67 bool ShenandoahPassiveHeuristics::should_unload_classes() { 68 // Always unload classes, if we can. 69 return can_unload_classes(); 70 } 71 72 bool ShenandoahPassiveHeuristics::should_degenerate_cycle() { 73 // Always fail to Degenerated GC, if enabled 74 return ShenandoahDegeneratedGC; 75 } 76 77 void ShenandoahPassiveHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset, 78 RegionData* data, size_t size, 79 size_t actual_free) { 80 assert(ShenandoahDegeneratedGC, "This path is only taken for Degenerated GC"); 81 82 // Do not select too large CSet that would overflow the available free space. 83 // Take at least the entire evacuation reserve, and be free to overflow to free space. 84 size_t capacity = ShenandoahHeap::heap()->max_capacity(); 85 size_t available = MAX2(capacity / 100 * ShenandoahEvacReserve, actual_free); 86 size_t max_cset = (size_t)(available / ShenandoahEvacWaste); 87 88 log_info(gc, ergo)("CSet Selection. Actual Free: " SIZE_FORMAT "M, Max CSet: " SIZE_FORMAT "M", 89 actual_free / M, max_cset / M); 90 91 size_t threshold = ShenandoahHeapRegion::region_size_bytes() * ShenandoahGarbageThreshold / 100; 92 93 size_t live_cset = 0; 94 for (size_t idx = 0; idx < size; idx++) { 95 ShenandoahHeapRegion* r = data[idx]._region; 96 size_t new_cset = live_cset + r->get_live_data_bytes(); 97 if (new_cset < max_cset && r->garbage() > threshold) { 98 live_cset = new_cset; 99 cset->add_region(r); 100 } 101 } 102 } 103 104 const char* ShenandoahPassiveHeuristics::name() { 105 return "passive"; 106 } 107 108 bool ShenandoahPassiveHeuristics::is_diagnostic() { 109 return true; 110 } 111 112 bool ShenandoahPassiveHeuristics::is_experimental() { 113 return false; 114 }