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1 /*
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2 * Copyright 1998-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 //
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26 // Prioritized queue of VM operations.
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27 //
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28 // Encapsulates both queue management and
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29 // and priority policy
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30 //
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31 class VMOperationQueue : public CHeapObj {
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32 private:
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33 enum Priorities {
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34 SafepointPriority, // Highest priority (operation executed at a safepoint)
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35 MediumPriority, // Medium priority
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36 nof_priorities
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37 };
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38
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39 // We maintain a doubled linked list, with explicit count.
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40 int _queue_length[nof_priorities];
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41 int _queue_counter;
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42 VM_Operation* _queue [nof_priorities];
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43 // we also allow the vmThread to register the ops it has drained so we
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44 // can scan them from oops_do
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45 VM_Operation* _drain_list;
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46
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47 // Double-linked non-empty list insert.
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48 void insert(VM_Operation* q,VM_Operation* n);
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49 void unlink(VM_Operation* q);
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50
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51 // Basic queue manipulation
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52 bool queue_empty (int prio);
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53 void queue_add_front (int prio, VM_Operation *op);
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54 void queue_add_back (int prio, VM_Operation *op);
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55 VM_Operation* queue_remove_front(int prio);
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56 void queue_oops_do(int queue, OopClosure* f);
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57 void drain_list_oops_do(OopClosure* f);
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58 VM_Operation* queue_drain(int prio);
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59 // lock-free query: may return the wrong answer but must not break
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60 bool queue_peek(int prio) { return _queue_length[prio] > 0; }
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61
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62 public:
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63 VMOperationQueue();
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64
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65 // Highlevel operations. Encapsulates policy
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66 bool add(VM_Operation *op);
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67 VM_Operation* remove_next(); // Returns next or null
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68 VM_Operation* remove_next_at_safepoint_priority() { return queue_remove_front(SafepointPriority); }
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69 VM_Operation* drain_at_safepoint_priority() { return queue_drain(SafepointPriority); }
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70 void set_drain_list(VM_Operation* list) { _drain_list = list; }
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71 bool peek_at_safepoint_priority() { return queue_peek(SafepointPriority); }
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72
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73 // GC support
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74 void oops_do(OopClosure* f);
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75
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76 void verify_queue(int prio) PRODUCT_RETURN;
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77 };
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78
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79
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80 //
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81 // A single VMThread (the primordial thread) spawns all other threads
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82 // and is itself used by other threads to offload heavy vm operations
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83 // like scavenge, garbage_collect etc.
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84 //
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85
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86 class VMThread: public Thread {
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87 private:
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88 static ThreadPriority _current_priority;
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89
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90 static bool _should_terminate;
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91 static bool _terminated;
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92 static Monitor * _terminate_lock;
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93 static PerfCounter* _perf_accumulated_vm_operation_time;
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94
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95 void evaluate_operation(VM_Operation* op);
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96 public:
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97 // Constructor
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98 VMThread();
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99
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100 // Tester
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101 bool is_VM_thread() const { return true; }
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102 bool is_GC_thread() const { return true; }
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103
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104 char* name() const { return (char*)"VM Thread"; }
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105
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106 // The ever running loop for the VMThread
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107 void loop();
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108
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109 // Called to stop the VM thread
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110 static void wait_for_vm_thread_exit();
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111 static bool should_terminate() { return _should_terminate; }
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112 static bool is_terminated() { return _terminated == true; }
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113
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114 // Execution of vm operation
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115 static void execute(VM_Operation* op);
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116
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117 // Returns the current vm operation if any.
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118 static VM_Operation* vm_operation() { return _cur_vm_operation; }
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119
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120 // Returns the single instance of VMThread.
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121 static VMThread* vm_thread() { return _vm_thread; }
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122
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123 // GC support
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124 void oops_do(OopClosure* f);
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125
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126 // Debugging
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127 void print_on(outputStream* st) const;
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128 void print() const { print_on(tty); }
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129 void verify();
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130
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131 // Performance measurement
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132 static PerfCounter* perf_accumulated_vm_operation_time() { return _perf_accumulated_vm_operation_time; }
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133
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134 // Entry for starting vm thread
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135 virtual void run();
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136
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137 // Creations/Destructions
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138 static void create();
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139 static void destroy();
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140
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141 private:
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142 // VM_Operation support
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143 static VM_Operation* _cur_vm_operation; // Current VM operation
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144 static VMOperationQueue* _vm_queue; // Queue (w/ policy) of VM operations
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145
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146 // Pointer to single-instance of VM thread
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147 static VMThread* _vm_thread;
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148 };
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