1 /* 2 * Copyright (c) 2001, 2018, 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 #ifndef SHARE_VM_GC_CMS_ALLOCATIONSTATS_HPP 26 #define SHARE_VM_GC_CMS_ALLOCATIONSTATS_HPP 27 28 #include "gc/shared/gcUtil.hpp" 29 #include "logging/log.hpp" 30 #include "utilities/globalDefinitions.hpp" 31 #include "utilities/macros.hpp" 32 33 class AllocationStats { 34 // A duration threshold (in ms) used to filter 35 // possibly unreliable samples. 36 static float _threshold; 37 38 // We measure the demand between the end of the previous sweep and 39 // beginning of this sweep: 40 // Count(end_last_sweep) - Count(start_this_sweep) 41 // + split_births(between) - split_deaths(between) 42 // The above number divided by the time since the end of the 43 // previous sweep gives us a time rate of demand for blocks 44 // of this size. We compute a padded average of this rate as 45 // our current estimate for the time rate of demand for blocks 46 // of this size. Similarly, we keep a padded average for the time 47 // between sweeps. Our current estimate for demand for blocks of 48 // this size is then simply computed as the product of these two 49 // estimates. 50 AdaptivePaddedAverage _demand_rate_estimate; 51 52 ssize_t _desired; // Demand estimate computed as described above 53 ssize_t _coal_desired; // desired +/- small-percent for tuning coalescing 54 55 ssize_t _surplus; // count - (desired +/- small-percent), 56 // used to tune splitting in best fit 57 ssize_t _bfr_surp; // surplus at start of current sweep 58 ssize_t _prev_sweep; // count from end of previous sweep 59 ssize_t _before_sweep; // count from before current sweep 60 ssize_t _coal_births; // additional chunks from coalescing 61 ssize_t _coal_deaths; // loss from coalescing 62 ssize_t _split_births; // additional chunks from splitting 63 ssize_t _split_deaths; // loss from splitting 64 size_t _returned_bytes; // number of bytes returned to list. 65 public: 66 void initialize(bool split_birth = false); 67 AllocationStats()68 AllocationStats() { 69 initialize(); 70 } 71 72 // The rate estimate is in blocks per second. compute_desired(size_t count,float inter_sweep_current,float inter_sweep_estimate,float intra_sweep_estimate)73 void compute_desired(size_t count, 74 float inter_sweep_current, 75 float inter_sweep_estimate, 76 float intra_sweep_estimate) { 77 // If the latest inter-sweep time is below our granularity 78 // of measurement, we may call in here with 79 // inter_sweep_current == 0. However, even for suitably small 80 // but non-zero inter-sweep durations, we may not trust the accuracy 81 // of accumulated data, since it has not been "integrated" 82 // (read "low-pass-filtered") long enough, and would be 83 // vulnerable to noisy glitches. In such cases, we 84 // ignore the current sample and use currently available 85 // historical estimates. 86 assert(prev_sweep() + split_births() + coal_births() // "Total Production Stock" 87 >= split_deaths() + coal_deaths() + (ssize_t)count, // "Current stock + depletion" 88 "Conservation Principle"); 89 if (inter_sweep_current > _threshold) { 90 ssize_t demand = prev_sweep() - (ssize_t)count + split_births() + coal_births() 91 - split_deaths() - coal_deaths(); 92 assert(demand >= 0, 93 "Demand (" SSIZE_FORMAT ") should be non-negative for " 94 PTR_FORMAT " (size=" SIZE_FORMAT ")", 95 demand, p2i(this), count); 96 // Defensive: adjust for imprecision in event counting 97 if (demand < 0) { 98 demand = 0; 99 } 100 float old_rate = _demand_rate_estimate.padded_average(); 101 float rate = ((float)demand)/inter_sweep_current; 102 _demand_rate_estimate.sample(rate); 103 float new_rate = _demand_rate_estimate.padded_average(); 104 ssize_t old_desired = _desired; 105 float delta_ise = (CMSExtrapolateSweep ? intra_sweep_estimate : 0.0); 106 _desired = (ssize_t)(new_rate * (inter_sweep_estimate + delta_ise)); 107 log_trace(gc, freelist)("demand: " SSIZE_FORMAT ", old_rate: %f, current_rate: %f, " 108 "new_rate: %f, old_desired: " SSIZE_FORMAT ", new_desired: " SSIZE_FORMAT, 109 demand, old_rate, rate, new_rate, old_desired, _desired); 110 } 111 } 112 desired() const113 ssize_t desired() const { return _desired; } set_desired(ssize_t v)114 void set_desired(ssize_t v) { _desired = v; } 115 coal_desired() const116 ssize_t coal_desired() const { return _coal_desired; } set_coal_desired(ssize_t v)117 void set_coal_desired(ssize_t v) { _coal_desired = v; } 118 surplus() const119 ssize_t surplus() const { return _surplus; } set_surplus(ssize_t v)120 void set_surplus(ssize_t v) { _surplus = v; } increment_surplus()121 void increment_surplus() { _surplus++; } decrement_surplus()122 void decrement_surplus() { _surplus--; } 123 bfr_surp() const124 ssize_t bfr_surp() const { return _bfr_surp; } set_bfr_surp(ssize_t v)125 void set_bfr_surp(ssize_t v) { _bfr_surp = v; } prev_sweep() const126 ssize_t prev_sweep() const { return _prev_sweep; } set_prev_sweep(ssize_t v)127 void set_prev_sweep(ssize_t v) { _prev_sweep = v; } before_sweep() const128 ssize_t before_sweep() const { return _before_sweep; } set_before_sweep(ssize_t v)129 void set_before_sweep(ssize_t v) { _before_sweep = v; } 130 coal_births() const131 ssize_t coal_births() const { return _coal_births; } set_coal_births(ssize_t v)132 void set_coal_births(ssize_t v) { _coal_births = v; } increment_coal_births()133 void increment_coal_births() { _coal_births++; } 134 coal_deaths() const135 ssize_t coal_deaths() const { return _coal_deaths; } set_coal_deaths(ssize_t v)136 void set_coal_deaths(ssize_t v) { _coal_deaths = v; } increment_coal_deaths()137 void increment_coal_deaths() { _coal_deaths++; } 138 split_births() const139 ssize_t split_births() const { return _split_births; } set_split_births(ssize_t v)140 void set_split_births(ssize_t v) { _split_births = v; } increment_split_births()141 void increment_split_births() { _split_births++; } 142 split_deaths() const143 ssize_t split_deaths() const { return _split_deaths; } set_split_deaths(ssize_t v)144 void set_split_deaths(ssize_t v) { _split_deaths = v; } increment_split_deaths()145 void increment_split_deaths() { _split_deaths++; } 146 147 NOT_PRODUCT( 148 size_t returned_bytes() const { return _returned_bytes; } 149 void set_returned_bytes(size_t v) { _returned_bytes = v; } 150 ) 151 }; 152 153 #endif // SHARE_VM_GC_CMS_ALLOCATIONSTATS_HPP 154