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1 /*
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2 * Copyright 1997-2005 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 # include "incls/_precompiled.incl"
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26 # include "incls/_sweeper.cpp.incl"
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27
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28 long NMethodSweeper::_traversals = 0; // No. of stack traversals performed
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29 CodeBlob* NMethodSweeper::_current = NULL; // Current nmethod
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30 int NMethodSweeper::_seen = 0 ; // No. of blobs we have currently processed in current pass of CodeCache
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31 int NMethodSweeper::_invocations = 0; // No. of invocations left until we are completed with this pass
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32
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33 jint NMethodSweeper::_locked_seen = 0;
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34 jint NMethodSweeper::_not_entrant_seen_on_stack = 0;
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35 bool NMethodSweeper::_rescan = false;
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36
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37 void NMethodSweeper::sweep() {
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38 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
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39 if (!MethodFlushing) return;
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40
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41 // No need to synchronize access, since this is always executed at a
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42 // safepoint. If we aren't in the middle of scan and a rescan
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43 // hasn't been requested then just return.
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44 if (_current == NULL && !_rescan) return;
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45
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46 // Make sure CompiledIC_lock in unlocked, since we might update some
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47 // inline caches. If it is, we just bail-out and try later.
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48 if (CompiledIC_lock->is_locked() || Patching_lock->is_locked()) return;
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49
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50 // Check for restart
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51 assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");
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52 if (_current == NULL) {
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53 _seen = 0;
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54 _invocations = NmethodSweepFraction;
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55 _current = CodeCache::first();
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56 _traversals += 1;
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57 if (PrintMethodFlushing) {
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58 tty->print_cr("### Sweep: stack traversal %d", _traversals);
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59 }
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60 Threads::nmethods_do();
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61
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62 // reset the flags since we started a scan from the beginning.
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63 _rescan = false;
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64 _locked_seen = 0;
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65 _not_entrant_seen_on_stack = 0;
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66 }
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67
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68 if (PrintMethodFlushing && Verbose) {
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69 tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_blobs(), _invocations);
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70 }
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71
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72 // We want to visit all nmethods after NmethodSweepFraction invocations.
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73 // If invocation is 1 we do the rest
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74 int todo = CodeCache::nof_blobs();
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75 if (_invocations != 1) {
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76 todo = (CodeCache::nof_blobs() - _seen) / _invocations;
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77 _invocations--;
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78 }
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79
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80 for(int i = 0; i < todo && _current != NULL; i++) {
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81 CodeBlob* next = CodeCache::next(_current); // Read next before we potentially delete current
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82 if (_current->is_nmethod()) {
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83 process_nmethod((nmethod *)_current);
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84 }
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85 _seen++;
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86 _current = next;
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87 }
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88 // Because we could stop on a codeBlob other than an nmethod we skip forward
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89 // to the next nmethod (if any). codeBlobs other than nmethods can be freed
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90 // async to us and make _current invalid while we sleep.
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91 while (_current != NULL && !_current->is_nmethod()) {
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92 _current = CodeCache::next(_current);
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93 }
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94
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95 if (_current == NULL && !_rescan && (_locked_seen || _not_entrant_seen_on_stack)) {
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96 // we've completed a scan without making progress but there were
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97 // nmethods we were unable to process either because they were
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98 // locked or were still on stack. We don't have to aggresively
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99 // clean them up so just stop scanning. We could scan once more
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100 // but that complicates the control logic and it's unlikely to
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101 // matter much.
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102 if (PrintMethodFlushing) {
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103 tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");
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104 }
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105 }
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106 }
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107
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108
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109 void NMethodSweeper::process_nmethod(nmethod *nm) {
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110 // Skip methods that are currently referenced by the VM
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111 if (nm->is_locked_by_vm()) {
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112 // But still remember to clean-up inline caches for alive nmethods
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113 if (nm->is_alive()) {
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114 // Clean-up all inline caches that points to zombie/non-reentrant methods
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115 nm->cleanup_inline_caches();
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116 } else {
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117 _locked_seen++;
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118 }
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119 return;
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120 }
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121
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122 if (nm->is_zombie()) {
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123 // If it is first time, we see nmethod then we mark it. Otherwise,
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124 // we reclame it. When we have seen a zombie method twice, we know that
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125 // there are no inline caches that referes to it.
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126 if (nm->is_marked_for_reclamation()) {
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127 assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
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941
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128 if (PrintMethodFlushing && Verbose) {
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129 tty->print_cr("### Nmethod 0x%x (marked for reclamation) being flushed", nm);
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130 }
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0
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131 nm->flush();
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132 } else {
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941
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133 if (PrintMethodFlushing && Verbose) {
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134 tty->print_cr("### Nmethod 0x%x (zombie) being marked for reclamation", nm);
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135 }
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0
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136 nm->mark_for_reclamation();
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137 _rescan = true;
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138 }
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139 } else if (nm->is_not_entrant()) {
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140 // If there is no current activations of this method on the
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141 // stack we can safely convert it to a zombie method
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142 if (nm->can_not_entrant_be_converted()) {
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941
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143 if (PrintMethodFlushing && Verbose) {
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144 tty->print_cr("### Nmethod 0x%x (not entrant) being made zombie", nm);
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145 }
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0
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146 nm->make_zombie();
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147 _rescan = true;
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148 } else {
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149 // Still alive, clean up its inline caches
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150 nm->cleanup_inline_caches();
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151 // we coudn't transition this nmethod so don't immediately
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152 // request a rescan. If this method stays on the stack for a
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153 // long time we don't want to keep rescanning at every safepoint.
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154 _not_entrant_seen_on_stack++;
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155 }
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156 } else if (nm->is_unloaded()) {
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157 // Unloaded code, just make it a zombie
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941
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158 if (PrintMethodFlushing && Verbose)
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159 tty->print_cr("### Nmethod 0x%x (unloaded) being made zombie", nm);
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160 if (nm->is_osr_method()) {
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0
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161 // No inline caches will ever point to osr methods, so we can just remove it
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162 nm->flush();
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163 } else {
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164 nm->make_zombie();
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165 _rescan = true;
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166 }
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167 } else {
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168 assert(nm->is_alive(), "should be alive");
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169 // Clean-up all inline caches that points to zombie/non-reentrant methods
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170 nm->cleanup_inline_caches();
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171 }
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172 }
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