comparison src/share/vm/runtime/sweeper.cpp @ 0:a61af66fc99e jdk7-b24

Initial load
author duke
date Sat, 01 Dec 2007 00:00:00 +0000
parents
children 8b46c4d82093 148e5441d916
comparison
equal deleted inserted replaced
-1:000000000000 0:a61af66fc99e
1 /*
2 * Copyright 1997-2005 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 # include "incls/_precompiled.incl"
26 # include "incls/_sweeper.cpp.incl"
27
28 long NMethodSweeper::_traversals = 0; // No. of stack traversals performed
29 CodeBlob* NMethodSweeper::_current = NULL; // Current nmethod
30 int NMethodSweeper::_seen = 0 ; // No. of blobs we have currently processed in current pass of CodeCache
31 int NMethodSweeper::_invocations = 0; // No. of invocations left until we are completed with this pass
32
33 jint NMethodSweeper::_locked_seen = 0;
34 jint NMethodSweeper::_not_entrant_seen_on_stack = 0;
35 bool NMethodSweeper::_rescan = false;
36
37 void NMethodSweeper::sweep() {
38 assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
39 if (!MethodFlushing) return;
40
41 // No need to synchronize access, since this is always executed at a
42 // safepoint. If we aren't in the middle of scan and a rescan
43 // hasn't been requested then just return.
44 if (_current == NULL && !_rescan) return;
45
46 // Make sure CompiledIC_lock in unlocked, since we might update some
47 // inline caches. If it is, we just bail-out and try later.
48 if (CompiledIC_lock->is_locked() || Patching_lock->is_locked()) return;
49
50 // Check for restart
51 assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");
52 if (_current == NULL) {
53 _seen = 0;
54 _invocations = NmethodSweepFraction;
55 _current = CodeCache::first();
56 _traversals += 1;
57 if (PrintMethodFlushing) {
58 tty->print_cr("### Sweep: stack traversal %d", _traversals);
59 }
60 Threads::nmethods_do();
61
62 // reset the flags since we started a scan from the beginning.
63 _rescan = false;
64 _locked_seen = 0;
65 _not_entrant_seen_on_stack = 0;
66 }
67
68 if (PrintMethodFlushing && Verbose) {
69 tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_blobs(), _invocations);
70 }
71
72 // We want to visit all nmethods after NmethodSweepFraction invocations.
73 // If invocation is 1 we do the rest
74 int todo = CodeCache::nof_blobs();
75 if (_invocations != 1) {
76 todo = (CodeCache::nof_blobs() - _seen) / _invocations;
77 _invocations--;
78 }
79
80 for(int i = 0; i < todo && _current != NULL; i++) {
81 CodeBlob* next = CodeCache::next(_current); // Read next before we potentially delete current
82 if (_current->is_nmethod()) {
83 process_nmethod((nmethod *)_current);
84 }
85 _seen++;
86 _current = next;
87 }
88 // Because we could stop on a codeBlob other than an nmethod we skip forward
89 // to the next nmethod (if any). codeBlobs other than nmethods can be freed
90 // async to us and make _current invalid while we sleep.
91 while (_current != NULL && !_current->is_nmethod()) {
92 _current = CodeCache::next(_current);
93 }
94
95 if (_current == NULL && !_rescan && (_locked_seen || _not_entrant_seen_on_stack)) {
96 // we've completed a scan without making progress but there were
97 // nmethods we were unable to process either because they were
98 // locked or were still on stack. We don't have to aggresively
99 // clean them up so just stop scanning. We could scan once more
100 // but that complicates the control logic and it's unlikely to
101 // matter much.
102 if (PrintMethodFlushing) {
103 tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");
104 }
105 }
106 }
107
108
109 void NMethodSweeper::process_nmethod(nmethod *nm) {
110 // Skip methods that are currently referenced by the VM
111 if (nm->is_locked_by_vm()) {
112 // But still remember to clean-up inline caches for alive nmethods
113 if (nm->is_alive()) {
114 // Clean-up all inline caches that points to zombie/non-reentrant methods
115 nm->cleanup_inline_caches();
116 } else {
117 _locked_seen++;
118 }
119 return;
120 }
121
122 if (nm->is_zombie()) {
123 // If it is first time, we see nmethod then we mark it. Otherwise,
124 // we reclame it. When we have seen a zombie method twice, we know that
125 // there are no inline caches that referes to it.
126 if (nm->is_marked_for_reclamation()) {
127 assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
128 nm->flush();
129 } else {
130 nm->mark_for_reclamation();
131 _rescan = true;
132 }
133 } else if (nm->is_not_entrant()) {
134 // If there is no current activations of this method on the
135 // stack we can safely convert it to a zombie method
136 if (nm->can_not_entrant_be_converted()) {
137 nm->make_zombie();
138 _rescan = true;
139 } else {
140 // Still alive, clean up its inline caches
141 nm->cleanup_inline_caches();
142 // we coudn't transition this nmethod so don't immediately
143 // request a rescan. If this method stays on the stack for a
144 // long time we don't want to keep rescanning at every safepoint.
145 _not_entrant_seen_on_stack++;
146 }
147 } else if (nm->is_unloaded()) {
148 // Unloaded code, just make it a zombie
149 if (nm->is_osr_only_method()) {
150 // No inline caches will ever point to osr methods, so we can just remove it
151 nm->flush();
152 } else {
153 nm->make_zombie();
154 _rescan = true;
155 }
156 } else {
157 assert(nm->is_alive(), "should be alive");
158 // Clean-up all inline caches that points to zombie/non-reentrant methods
159 nm->cleanup_inline_caches();
160 }
161 }