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1 /*
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948
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2 * Copyright 1997-2009 Sun Microsystems, Inc. All Rights Reserved.
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0
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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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1202
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36 bool NMethodSweeper::_was_full = false;
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37 jint NMethodSweeper::_advise_to_sweep = 0;
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38 jlong NMethodSweeper::_last_was_full = 0;
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39 uint NMethodSweeper::_highest_marked = 0;
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40 long NMethodSweeper::_was_full_traversal = 0;
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0
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41
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989
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42 class MarkActivationClosure: public CodeBlobClosure {
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43 public:
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44 virtual void do_code_blob(CodeBlob* cb) {
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45 // If we see an activation belonging to a non_entrant nmethod, we mark it.
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46 if (cb->is_nmethod() && ((nmethod*)cb)->is_not_entrant()) {
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47 ((nmethod*)cb)->mark_as_seen_on_stack();
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48 }
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49 }
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50 };
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51 static MarkActivationClosure mark_activation_closure;
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52
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0
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53 void NMethodSweeper::sweep() {
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54 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
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55 if (!MethodFlushing) return;
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56
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57 // No need to synchronize access, since this is always executed at a
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58 // safepoint. If we aren't in the middle of scan and a rescan
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59 // hasn't been requested then just return.
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60 if (_current == NULL && !_rescan) return;
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61
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62 // Make sure CompiledIC_lock in unlocked, since we might update some
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63 // inline caches. If it is, we just bail-out and try later.
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64 if (CompiledIC_lock->is_locked() || Patching_lock->is_locked()) return;
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65
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66 // Check for restart
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67 assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");
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68 if (_current == NULL) {
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69 _seen = 0;
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70 _invocations = NmethodSweepFraction;
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71 _current = CodeCache::first();
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72 _traversals += 1;
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73 if (PrintMethodFlushing) {
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74 tty->print_cr("### Sweep: stack traversal %d", _traversals);
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75 }
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989
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76 Threads::nmethods_do(&mark_activation_closure);
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0
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77
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78 // reset the flags since we started a scan from the beginning.
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79 _rescan = false;
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80 _locked_seen = 0;
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81 _not_entrant_seen_on_stack = 0;
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82 }
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83
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84 if (PrintMethodFlushing && Verbose) {
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85 tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_blobs(), _invocations);
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86 }
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87
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88 // We want to visit all nmethods after NmethodSweepFraction invocations.
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89 // If invocation is 1 we do the rest
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90 int todo = CodeCache::nof_blobs();
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91 if (_invocations != 1) {
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92 todo = (CodeCache::nof_blobs() - _seen) / _invocations;
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93 _invocations--;
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94 }
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95
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96 for(int i = 0; i < todo && _current != NULL; i++) {
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97 CodeBlob* next = CodeCache::next(_current); // Read next before we potentially delete current
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98 if (_current->is_nmethod()) {
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99 process_nmethod((nmethod *)_current);
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100 }
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101 _seen++;
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102 _current = next;
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103 }
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104 // Because we could stop on a codeBlob other than an nmethod we skip forward
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105 // to the next nmethod (if any). codeBlobs other than nmethods can be freed
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106 // async to us and make _current invalid while we sleep.
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107 while (_current != NULL && !_current->is_nmethod()) {
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108 _current = CodeCache::next(_current);
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109 }
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110
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111 if (_current == NULL && !_rescan && (_locked_seen || _not_entrant_seen_on_stack)) {
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112 // we've completed a scan without making progress but there were
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113 // nmethods we were unable to process either because they were
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114 // locked or were still on stack. We don't have to aggresively
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115 // clean them up so just stop scanning. We could scan once more
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116 // but that complicates the control logic and it's unlikely to
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117 // matter much.
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118 if (PrintMethodFlushing) {
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119 tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");
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120 }
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121 }
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1202
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122
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123 if (UseCodeCacheFlushing) {
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124 if (!CodeCache::needs_flushing()) {
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125 // In a safepoint, no race with setters
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126 _advise_to_sweep = 0;
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127 }
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128
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129 if (was_full()) {
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130 // There was some progress so attempt to restart the compiler
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131 jlong now = os::javaTimeMillis();
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132 jlong max_interval = (jlong)MinCodeCacheFlushingInterval * (jlong)1000;
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133 jlong curr_interval = now - _last_was_full;
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134 if ((!CodeCache::needs_flushing()) && (curr_interval > max_interval)) {
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135 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
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136 set_was_full(false);
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137
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138 // Update the _last_was_full time so we can tell how fast the
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139 // code cache is filling up
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140 _last_was_full = os::javaTimeMillis();
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141
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142 if (PrintMethodFlushing) {
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143 tty->print_cr("### sweeper: Live blobs:" UINT32_FORMAT "/Free code cache:" SIZE_FORMAT " bytes, restarting compiler",
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144 CodeCache::nof_blobs(), CodeCache::unallocated_capacity());
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145 }
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146 if (LogCompilation && (xtty != NULL)) {
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147 ttyLocker ttyl;
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148 xtty->begin_elem("restart_compiler live_blobs='" UINT32_FORMAT "' free_code_cache='" SIZE_FORMAT "'",
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149 CodeCache::nof_blobs(), CodeCache::unallocated_capacity());
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150 xtty->stamp();
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151 xtty->end_elem();
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152 }
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153 }
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154 }
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155 }
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0
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156 }
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157
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158
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159 void NMethodSweeper::process_nmethod(nmethod *nm) {
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160 // Skip methods that are currently referenced by the VM
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161 if (nm->is_locked_by_vm()) {
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162 // But still remember to clean-up inline caches for alive nmethods
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163 if (nm->is_alive()) {
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164 // Clean-up all inline caches that points to zombie/non-reentrant methods
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165 nm->cleanup_inline_caches();
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166 } else {
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167 _locked_seen++;
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168 }
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169 return;
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170 }
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171
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172 if (nm->is_zombie()) {
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173 // If it is first time, we see nmethod then we mark it. Otherwise,
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174 // we reclame it. When we have seen a zombie method twice, we know that
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175 // there are no inline caches that referes to it.
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176 if (nm->is_marked_for_reclamation()) {
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177 assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
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941
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178 if (PrintMethodFlushing && Verbose) {
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1202
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179 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm);
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941
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180 }
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0
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181 nm->flush();
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182 } else {
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941
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183 if (PrintMethodFlushing && Verbose) {
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1202
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184 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);
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941
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185 }
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0
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186 nm->mark_for_reclamation();
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187 _rescan = true;
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188 }
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189 } else if (nm->is_not_entrant()) {
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190 // If there is no current activations of this method on the
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191 // stack we can safely convert it to a zombie method
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192 if (nm->can_not_entrant_be_converted()) {
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941
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193 if (PrintMethodFlushing && Verbose) {
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1202
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194 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);
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941
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195 }
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0
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196 nm->make_zombie();
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197 _rescan = true;
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198 } else {
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199 // Still alive, clean up its inline caches
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200 nm->cleanup_inline_caches();
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201 // we coudn't transition this nmethod so don't immediately
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202 // request a rescan. If this method stays on the stack for a
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203 // long time we don't want to keep rescanning at every safepoint.
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204 _not_entrant_seen_on_stack++;
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205 }
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206 } else if (nm->is_unloaded()) {
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207 // Unloaded code, just make it a zombie
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941
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208 if (PrintMethodFlushing && Verbose)
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1202
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209 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm);
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941
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210 if (nm->is_osr_method()) {
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0
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211 // No inline caches will ever point to osr methods, so we can just remove it
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212 nm->flush();
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213 } else {
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214 nm->make_zombie();
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215 _rescan = true;
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216 }
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217 } else {
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218 assert(nm->is_alive(), "should be alive");
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1202
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219
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220 if (UseCodeCacheFlushing) {
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221 if ((nm->method()->code() != nm) && !(nm->is_locked_by_vm()) && !(nm->is_osr_method()) &&
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222 (_traversals > _was_full_traversal+2) && (((uint)nm->compile_id()) < _highest_marked) &&
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223 CodeCache::needs_flushing()) {
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224 // This method has not been called since the forced cleanup happened
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225 nm->make_not_entrant();
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226 }
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227 }
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228
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0
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229 // Clean-up all inline caches that points to zombie/non-reentrant methods
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230 nm->cleanup_inline_caches();
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231 }
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232 }
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1202
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233
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234 // Code cache unloading: when compilers notice the code cache is getting full,
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235 // they will call a vm op that comes here. This code attempts to speculatively
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236 // unload the oldest half of the nmethods (based on the compile job id) by
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237 // saving the old code in a list in the CodeCache. Then
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238 // execution resumes. If a method so marked is not called by the second
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239 // safepoint from the current one, the nmethod will be marked non-entrant and
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240 // got rid of by normal sweeping. If the method is called, the methodOop's
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241 // _code field is restored and the methodOop/nmethod
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242 // go back to their normal state.
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243 void NMethodSweeper::handle_full_code_cache(bool is_full) {
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244 // Only the first one to notice can advise us to start early cleaning
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245 if (!is_full){
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246 jint old = Atomic::cmpxchg( 1, &_advise_to_sweep, 0 );
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247 if (old != 0) {
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248 return;
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249 }
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250 }
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251
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252 if (is_full) {
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253 // Since code cache is full, immediately stop new compiles
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254 bool did_set = CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation);
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255 if (!did_set) {
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256 // only the first to notice can start the cleaning,
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257 // others will go back and block
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258 return;
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259 }
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260 set_was_full(true);
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261
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262 // If we run out within MinCodeCacheFlushingInterval of the last unload time, give up
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263 jlong now = os::javaTimeMillis();
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264 jlong max_interval = (jlong)MinCodeCacheFlushingInterval * (jlong)1000;
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265 jlong curr_interval = now - _last_was_full;
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266 if (curr_interval < max_interval) {
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267 _rescan = true;
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268 if (PrintMethodFlushing) {
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269 tty->print_cr("### handle full too often, turning off compiler");
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270 }
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271 if (LogCompilation && (xtty != NULL)) {
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272 ttyLocker ttyl;
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273 xtty->begin_elem("disable_compiler flushing_interval='" UINT64_FORMAT "' live_blobs='" UINT32_FORMAT "' free_code_cache='" SIZE_FORMAT "'",
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274 curr_interval/1000, CodeCache::nof_blobs(), CodeCache::unallocated_capacity());
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275 xtty->stamp();
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276 xtty->end_elem();
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277 }
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278 return;
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279 }
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280 }
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281
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282 VM_HandleFullCodeCache op(is_full);
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283 VMThread::execute(&op);
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284
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285 // rescan again as soon as possible
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286 _rescan = true;
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287 }
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288
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289 void NMethodSweeper::speculative_disconnect_nmethods(bool is_full) {
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290 // If there was a race in detecting full code cache, only run
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291 // one vm op for it or keep the compiler shut off
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292
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293 debug_only(jlong start = os::javaTimeMillis();)
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294
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295 if ((!was_full()) && (is_full)) {
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296 if (!CodeCache::needs_flushing()) {
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297 if (PrintMethodFlushing) {
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298 tty->print_cr("### sweeper: Live blobs:" UINT32_FORMAT "/Free code cache:" SIZE_FORMAT " bytes, restarting compiler",
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299 CodeCache::nof_blobs(), CodeCache::unallocated_capacity());
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300 }
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301 if (LogCompilation && (xtty != NULL)) {
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302 ttyLocker ttyl;
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303 xtty->begin_elem("restart_compiler live_blobs='" UINT32_FORMAT "' free_code_cache='" SIZE_FORMAT "'",
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304 CodeCache::nof_blobs(), CodeCache::unallocated_capacity());
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305 xtty->stamp();
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306 xtty->end_elem();
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307 }
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308 CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
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309 return;
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310 }
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311 }
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312
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313 // Traverse the code cache trying to dump the oldest nmethods
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314 uint curr_max_comp_id = CompileBroker::get_compilation_id();
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315 uint flush_target = ((curr_max_comp_id - _highest_marked) >> 1) + _highest_marked;
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316 if (PrintMethodFlushing && Verbose) {
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317 tty->print_cr("### Cleaning code cache: Live blobs:" UINT32_FORMAT "/Free code cache:" SIZE_FORMAT " bytes",
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318 CodeCache::nof_blobs(), CodeCache::unallocated_capacity());
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319 }
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320 if (LogCompilation && (xtty != NULL)) {
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321 ttyLocker ttyl;
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322 xtty->begin_elem("start_cleaning_code_cache live_blobs='" UINT32_FORMAT "' free_code_cache='" SIZE_FORMAT "'",
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323 CodeCache::nof_blobs(), CodeCache::unallocated_capacity());
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324 xtty->stamp();
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325 xtty->end_elem();
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326 }
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327
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328 nmethod* nm = CodeCache::alive_nmethod(CodeCache::first());
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329 jint disconnected = 0;
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330 jint made_not_entrant = 0;
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331 while ((nm != NULL)){
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332 uint curr_comp_id = nm->compile_id();
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333
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334 // OSR methods cannot be flushed like this. Also, don't flush native methods
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335 // since they are part of the JDK in most cases
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336 if (nm->is_in_use() && (!nm->is_osr_method()) && (!nm->is_locked_by_vm()) &&
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337 (!nm->is_native_method()) && ((curr_comp_id < flush_target))) {
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338
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339 if ((nm->method()->code() == nm)) {
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340 // This method has not been previously considered for
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341 // unloading or it was restored already
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342 CodeCache::speculatively_disconnect(nm);
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343 disconnected++;
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344 } else if (nm->is_speculatively_disconnected()) {
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345 // This method was previously considered for preemptive unloading and was not called since then
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346 nm->method()->invocation_counter()->decay();
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347 nm->method()->backedge_counter()->decay();
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348 nm->make_not_entrant();
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349 made_not_entrant++;
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350 }
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351
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352 if (curr_comp_id > _highest_marked) {
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353 _highest_marked = curr_comp_id;
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354 }
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355 }
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356 nm = CodeCache::alive_nmethod(CodeCache::next(nm));
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357 }
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358
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359 if (LogCompilation && (xtty != NULL)) {
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360 ttyLocker ttyl;
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361 xtty->begin_elem("stop_cleaning_code_cache disconnected='" UINT32_FORMAT "' made_not_entrant='" UINT32_FORMAT "' live_blobs='" UINT32_FORMAT "' free_code_cache='" SIZE_FORMAT "'",
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362 disconnected, made_not_entrant, CodeCache::nof_blobs(), CodeCache::unallocated_capacity());
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363 xtty->stamp();
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364 xtty->end_elem();
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365 }
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366
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367 // Shut off compiler. Sweeper will run exiting from this safepoint
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368 // and turn it back on if it clears enough space
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369 if (was_full()) {
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370 _last_was_full = os::javaTimeMillis();
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371 CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation);
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372 }
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373
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374 // After two more traversals the sweeper will get rid of unrestored nmethods
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375 _was_full_traversal = _traversals;
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376 #ifdef ASSERT
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377 jlong end = os::javaTimeMillis();
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378 if(PrintMethodFlushing && Verbose) {
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379 tty->print_cr("### sweeper: unload time: " INT64_FORMAT, end-start);
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380 }
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381 #endif
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382 }
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