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17780
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1 /*
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2 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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20 * or visit www.oracle.com if you need additional information or have any
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21 * questions.
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22 *
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23 */
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24
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25 #ifndef SHARE_VM_RUNTIME_RTMLOCKING_HPP
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26 #define SHARE_VM_RUNTIME_RTMLOCKING_HPP
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27
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28 // Generate RTM (Restricted Transactional Memory) locking code for all inflated
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29 // locks when "UseRTMLocking" option is on with normal locking mechanism as fall back
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30 // handler.
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31 //
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32 // On abort/lock busy the lock will be retried a fixed number of times under RTM
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33 // as specified by "RTMRetryCount" option. The locks which abort too often
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34 // can be auto tuned or manually tuned.
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35 //
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36 // Auto-tuning can be done on an option like UseRTMDeopt and it will need abort
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37 // ratio calculation for each lock. The abort ratio will be calculated after
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38 // "RTMAbortThreshold" number of aborts is reached. The formulas are:
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39 //
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40 // Aborted transactions = abort_count * 100
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41 // All transactions = total_count * RTMTotalCountIncrRate
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42 //
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43 // Aborted transactions >= All transactions * RTMAbortRatio
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44 //
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45 // If "UseRTMDeopt" is on and the aborts ratio reaches "RTMAbortRatio"
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46 // the method containing the lock will be deoptimized and recompiled with
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47 // all locks as normal locks. If the abort ratio continues to remain low after
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48 // "RTMLockingThreshold" locks are attempted, then the method will be deoptimized
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49 // and recompiled with all locks as RTM locks without abort ratio calculation code.
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50 // The abort ratio calculation can be delayed by specifying flag
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51 // -XX:RTMLockingCalculationDelay in millisecond.
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52 //
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53 // For manual tuning the abort statistics for each lock needs to be provided
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54 // to the user on some JVM option like "PrintPreciseRTMLockingStatistics".
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55 // Based on the abort statistics users can create a .hotspot_compiler file
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56 // or use -XX:CompileCommand=option,class::method,NoRTMLockEliding
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57 // to specify for which methods to disable RTM locking.
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58 //
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59 // When UseRTMForStackLocks option is enabled along with UseRTMLocking option,
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60 // the RTM locking code is generated for stack locks too.
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61 // The retries, auto-tuning support and rtm locking statistics are all
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62 // supported for stack locks just like inflated locks.
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63
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64 // RTM locking counters
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65 class RTMLockingCounters VALUE_OBJ_CLASS_SPEC {
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66 private:
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67 uintx _total_count; // Total RTM locks count
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68 uintx _abort_count; // Total aborts count
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69
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70 public:
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71 enum { ABORT_STATUS_LIMIT = 6 };
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72 // Counters per RTM Abort Status. Incremented with +PrintPreciseRTMLockingStatistics
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73 // RTM uses the EAX register to communicate abort status to software.
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74 // Following an RTM abort the EAX register has the following definition.
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75 //
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76 // EAX register bit position Meaning
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77 // 0 Set if abort caused by XABORT instruction.
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78 // 1 If set, the transaction may succeed on a retry. This bit is always clear if bit 0 is set.
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79 // 2 Set if another logical processor conflicted with a memory address that was part of the transaction that aborted.
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80 // 3 Set if an internal buffer overflowed.
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81 // 4 Set if a debug breakpoint was hit.
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82 // 5 Set if an abort occurred during execution of a nested transaction.
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83 private:
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84 uintx _abortX_count[ABORT_STATUS_LIMIT];
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85
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86 public:
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87 static uintx _calculation_flag;
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88 static uintx* rtm_calculation_flag_addr() { return &_calculation_flag; }
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89
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90 static void init();
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91
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92 RTMLockingCounters() : _total_count(0), _abort_count(0) {
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93 for (int i = 0; i < ABORT_STATUS_LIMIT; i++) {
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94 _abortX_count[i] = 0;
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95 }
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96 }
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97
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98 uintx* total_count_addr() { return &_total_count; }
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99 uintx* abort_count_addr() { return &_abort_count; }
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100 uintx* abortX_count_addr() { return &_abortX_count[0]; }
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101
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102 static int total_count_offset() { return (int)offset_of(RTMLockingCounters, _total_count); }
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103 static int abort_count_offset() { return (int)offset_of(RTMLockingCounters, _abort_count); }
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104 static int abortX_count_offset() { return (int)offset_of(RTMLockingCounters, _abortX_count[0]); }
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105
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106
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107 bool nonzero() { return (_abort_count + _total_count) > 0; }
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108
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109 void print_on(outputStream* st);
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110 void print() { print_on(tty); }
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111 };
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112
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113 #endif // SHARE_VM_RUNTIME_RTMLOCKING_HPP
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