1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/vm/runtime/sweeper.cpp Sat Dec 01 00:00:00 2007 +0000
1.3 @@ -0,0 +1,161 @@
1.4 +/*
1.5 + * Copyright 1997-2005 Sun Microsystems, Inc. All Rights Reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation.
1.11 + *
1.12 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.13 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.14 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.15 + * version 2 for more details (a copy is included in the LICENSE file that
1.16 + * accompanied this code).
1.17 + *
1.18 + * You should have received a copy of the GNU General Public License version
1.19 + * 2 along with this work; if not, write to the Free Software Foundation,
1.20 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.21 + *
1.22 + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
1.23 + * CA 95054 USA or visit www.sun.com if you need additional information or
1.24 + * have any questions.
1.25 + *
1.26 + */
1.27 +
1.28 +# include "incls/_precompiled.incl"
1.29 +# include "incls/_sweeper.cpp.incl"
1.30 +
1.31 +long NMethodSweeper::_traversals = 0; // No. of stack traversals performed
1.32 +CodeBlob* NMethodSweeper::_current = NULL; // Current nmethod
1.33 +int NMethodSweeper::_seen = 0 ; // No. of blobs we have currently processed in current pass of CodeCache
1.34 +int NMethodSweeper::_invocations = 0; // No. of invocations left until we are completed with this pass
1.35 +
1.36 +jint NMethodSweeper::_locked_seen = 0;
1.37 +jint NMethodSweeper::_not_entrant_seen_on_stack = 0;
1.38 +bool NMethodSweeper::_rescan = false;
1.39 +
1.40 +void NMethodSweeper::sweep() {
1.41 + assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
1.42 + if (!MethodFlushing) return;
1.43 +
1.44 + // No need to synchronize access, since this is always executed at a
1.45 + // safepoint. If we aren't in the middle of scan and a rescan
1.46 + // hasn't been requested then just return.
1.47 + if (_current == NULL && !_rescan) return;
1.48 +
1.49 + // Make sure CompiledIC_lock in unlocked, since we might update some
1.50 + // inline caches. If it is, we just bail-out and try later.
1.51 + if (CompiledIC_lock->is_locked() || Patching_lock->is_locked()) return;
1.52 +
1.53 + // Check for restart
1.54 + assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");
1.55 + if (_current == NULL) {
1.56 + _seen = 0;
1.57 + _invocations = NmethodSweepFraction;
1.58 + _current = CodeCache::first();
1.59 + _traversals += 1;
1.60 + if (PrintMethodFlushing) {
1.61 + tty->print_cr("### Sweep: stack traversal %d", _traversals);
1.62 + }
1.63 + Threads::nmethods_do();
1.64 +
1.65 + // reset the flags since we started a scan from the beginning.
1.66 + _rescan = false;
1.67 + _locked_seen = 0;
1.68 + _not_entrant_seen_on_stack = 0;
1.69 + }
1.70 +
1.71 + if (PrintMethodFlushing && Verbose) {
1.72 + tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_blobs(), _invocations);
1.73 + }
1.74 +
1.75 + // We want to visit all nmethods after NmethodSweepFraction invocations.
1.76 + // If invocation is 1 we do the rest
1.77 + int todo = CodeCache::nof_blobs();
1.78 + if (_invocations != 1) {
1.79 + todo = (CodeCache::nof_blobs() - _seen) / _invocations;
1.80 + _invocations--;
1.81 + }
1.82 +
1.83 + for(int i = 0; i < todo && _current != NULL; i++) {
1.84 + CodeBlob* next = CodeCache::next(_current); // Read next before we potentially delete current
1.85 + if (_current->is_nmethod()) {
1.86 + process_nmethod((nmethod *)_current);
1.87 + }
1.88 + _seen++;
1.89 + _current = next;
1.90 + }
1.91 + // Because we could stop on a codeBlob other than an nmethod we skip forward
1.92 + // to the next nmethod (if any). codeBlobs other than nmethods can be freed
1.93 + // async to us and make _current invalid while we sleep.
1.94 + while (_current != NULL && !_current->is_nmethod()) {
1.95 + _current = CodeCache::next(_current);
1.96 + }
1.97 +
1.98 + if (_current == NULL && !_rescan && (_locked_seen || _not_entrant_seen_on_stack)) {
1.99 + // we've completed a scan without making progress but there were
1.100 + // nmethods we were unable to process either because they were
1.101 + // locked or were still on stack. We don't have to aggresively
1.102 + // clean them up so just stop scanning. We could scan once more
1.103 + // but that complicates the control logic and it's unlikely to
1.104 + // matter much.
1.105 + if (PrintMethodFlushing) {
1.106 + tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");
1.107 + }
1.108 + }
1.109 +}
1.110 +
1.111 +
1.112 +void NMethodSweeper::process_nmethod(nmethod *nm) {
1.113 + // Skip methods that are currently referenced by the VM
1.114 + if (nm->is_locked_by_vm()) {
1.115 + // But still remember to clean-up inline caches for alive nmethods
1.116 + if (nm->is_alive()) {
1.117 + // Clean-up all inline caches that points to zombie/non-reentrant methods
1.118 + nm->cleanup_inline_caches();
1.119 + } else {
1.120 + _locked_seen++;
1.121 + }
1.122 + return;
1.123 + }
1.124 +
1.125 + if (nm->is_zombie()) {
1.126 + // If it is first time, we see nmethod then we mark it. Otherwise,
1.127 + // we reclame it. When we have seen a zombie method twice, we know that
1.128 + // there are no inline caches that referes to it.
1.129 + if (nm->is_marked_for_reclamation()) {
1.130 + assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
1.131 + nm->flush();
1.132 + } else {
1.133 + nm->mark_for_reclamation();
1.134 + _rescan = true;
1.135 + }
1.136 + } else if (nm->is_not_entrant()) {
1.137 + // If there is no current activations of this method on the
1.138 + // stack we can safely convert it to a zombie method
1.139 + if (nm->can_not_entrant_be_converted()) {
1.140 + nm->make_zombie();
1.141 + _rescan = true;
1.142 + } else {
1.143 + // Still alive, clean up its inline caches
1.144 + nm->cleanup_inline_caches();
1.145 + // we coudn't transition this nmethod so don't immediately
1.146 + // request a rescan. If this method stays on the stack for a
1.147 + // long time we don't want to keep rescanning at every safepoint.
1.148 + _not_entrant_seen_on_stack++;
1.149 + }
1.150 + } else if (nm->is_unloaded()) {
1.151 + // Unloaded code, just make it a zombie
1.152 + if (nm->is_osr_only_method()) {
1.153 + // No inline caches will ever point to osr methods, so we can just remove it
1.154 + nm->flush();
1.155 + } else {
1.156 + nm->make_zombie();
1.157 + _rescan = true;
1.158 + }
1.159 + } else {
1.160 + assert(nm->is_alive(), "should be alive");
1.161 + // Clean-up all inline caches that points to zombie/non-reentrant methods
1.162 + nm->cleanup_inline_caches();
1.163 + }
1.164 +}
