Mercurial > hg > truffle

comparison src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp @ 0:a61af66fc99e jdk7-b24

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Initial load
author duke
date Sat, 01 Dec 2007 00:00:00 +0000
parents
children c18cbe5936b8
comparison
equal deleted inserted replaced
-1:000000000000 0:a61af66fc99e
1 /*
2 * Copyright 2001-2006 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 class ConcurrentMarkSweepGeneration;
26 class CMSCollector;
27
28 // The Concurrent Mark Sweep GC Thread (could be several in the future).
29 class ConcurrentMarkSweepThread: public ConcurrentGCThread {
30 friend class VMStructs;
31 friend class ConcurrentMarkSweepGeneration; // XXX should remove friendship
32 friend class CMSCollector;
33 public:
34 virtual void run();
35
36 private:
37 static ConcurrentMarkSweepThread* _cmst;
38 static CMSCollector* _collector;
39 static SurrogateLockerThread* _slt;
40 static SurrogateLockerThread::SLT_msg_type _sltBuffer;
41 static Monitor* _sltMonitor;
42
43 ConcurrentMarkSweepThread* _next;
44
45 static bool _should_terminate;
46
47 enum CMS_flag_type {
48 CMS_nil = NoBits,
49 CMS_cms_wants_token = nth_bit(0),
50 CMS_cms_has_token = nth_bit(1),
51 CMS_vm_wants_token = nth_bit(2),
52 CMS_vm_has_token = nth_bit(3)
53 };
54
55 static int _CMS_flag;
56
57 static bool CMS_flag_is_set(int b) { return (_CMS_flag & b) != 0; }
58 static bool set_CMS_flag(int b) { return (_CMS_flag |= b) != 0; }
59 static bool clear_CMS_flag(int b) { return (_CMS_flag &= ~b) != 0; }
60 void sleepBeforeNextCycle();
61
62 // CMS thread should yield for a young gen collection, direct allocation,
63 // and iCMS activity.
64 static char _pad_1[64 - sizeof(jint)]; // prevent cache-line sharing
65 static volatile jint _pending_yields;
66 static volatile jint _pending_decrements; // decrements to _pending_yields
67 static char _pad_2[64 - sizeof(jint)]; // prevent cache-line sharing
68
69 // Tracing messages, enabled by CMSTraceThreadState.
70 static inline void trace_state(const char* desc);
71
72 static volatile bool _icms_enabled; // iCMS enabled?
73 static volatile bool _should_run; // iCMS may run
74 static volatile bool _should_stop; // iCMS should stop
75
76 // debugging
77 void verify_ok_to_terminate() const PRODUCT_RETURN;
78
79 public:
80 // Constructor
81 ConcurrentMarkSweepThread(CMSCollector* collector);
82
83 static void makeSurrogateLockerThread(TRAPS);
84 static SurrogateLockerThread* slt() { return _slt; }
85
86 // Tester
87 bool is_ConcurrentGC_thread() const { return true; }
88
89 static void threads_do(ThreadClosure* tc);
90
91 // Printing
92 void print_on(outputStream* st) const;
93 void print() const { print_on(tty); }
94 static void print_all_on(outputStream* st);
95 static void print_all() { print_all_on(tty); }
96
97 // Returns the CMS Thread
98 static ConcurrentMarkSweepThread* cmst() { return _cmst; }
99 static CMSCollector* collector() { return _collector; }
100
101 // Create and start the CMS Thread, or stop it on shutdown
102 static ConcurrentMarkSweepThread* start(CMSCollector* collector);
103 static void stop();
104 static bool should_terminate() { return _should_terminate; }
105
106 // Synchronization using CMS token
107 static void synchronize(bool is_cms_thread);
108 static void desynchronize(bool is_cms_thread);
109 static bool vm_thread_has_cms_token() {
110 return CMS_flag_is_set(CMS_vm_has_token);
111 }
112 static bool cms_thread_has_cms_token() {
113 return CMS_flag_is_set(CMS_cms_has_token);
114 }
115 static bool vm_thread_wants_cms_token() {
116 return CMS_flag_is_set(CMS_vm_wants_token);
117 }
118 static bool cms_thread_wants_cms_token() {
119 return CMS_flag_is_set(CMS_cms_wants_token);
120 }
121
122 // Wait on CMS lock until the next synchronous GC
123 // or given timeout, whichever is earlier.
124 void wait_on_cms_lock(long t); // milliseconds
125
126 // The CMS thread will yield during the work portion of it's cycle
127 // only when requested to. Both synchronous and asychronous requests
128 // are provided. A synchronous request is used for young gen
129 // collections and direct allocations. The requesting thread increments
130 // pending_yields at the beginning of an operation, and decrements it when
131 // the operation is completed. The CMS thread yields when pending_yields
132 // is positive. An asynchronous request is used by iCMS in the stop_icms()
133 // operation. A single yield satisfies the outstanding asynch yield requests.
134 // The requesting thread increments both pending_yields and pending_decrements.
135 // After yielding, the CMS thread decrements both by the amount in
136 // pending_decrements.
137 // Note that, while "_pending_yields >= _pending_decrements" is an invariant,
138 // we cannot easily test that invariant, since the counters are manipulated via
139 // atomic instructions without explicit locking and we cannot read
140 // the two counters atomically together: one suggestion is to
141 // use (for example) 16-bit counters so as to be able to read the
142 // two counters atomically even on 32-bit platforms. Notice that
143 // the second assert in acknowledge_yield_request() does indeed
144 // check a form of the above invariant, albeit indirectly.
145
146 static void increment_pending_yields() {
147 Atomic::inc(&_pending_yields);
148 assert(_pending_yields >= 0, "can't be negative");
149 }
150 static void decrement_pending_yields() {
151 Atomic::dec(&_pending_yields);
152 assert(_pending_yields >= 0, "can't be negative");
153 }
154 static void asynchronous_yield_request() {
155 increment_pending_yields();
156 Atomic::inc(&_pending_decrements);
157 assert(_pending_decrements >= 0, "can't be negative");
158 }
159 static void acknowledge_yield_request() {
160 jint decrement = _pending_decrements;
161 if (decrement > 0) {
162 // Order important to preserve: _pending_yields >= _pending_decrements
163 Atomic::add(-decrement, &_pending_decrements);
164 Atomic::add(-decrement, &_pending_yields);
165 assert(_pending_decrements >= 0, "can't be negative");
166 assert(_pending_yields >= 0, "can't be negative");
167 }
168 }
169 static bool should_yield() { return _pending_yields > 0; }
170
171 // CMS incremental mode.
172 static void start_icms(); // notify thread to start a quantum of work
173 static void stop_icms(); // request thread to stop working
174 void icms_wait(); // if asked to stop, wait until notified to start
175
176 // Incremental mode is enabled globally by the flag CMSIncrementalMode. It
177 // must also be enabled/disabled dynamically to allow foreground collections.
178 static inline void enable_icms() { _icms_enabled = true; }
179 static inline void disable_icms() { _icms_enabled = false; }
180 static inline void set_icms_enabled(bool val) { _icms_enabled = val; }
181 static inline bool icms_enabled() { return _icms_enabled; }
182 };
183
184 inline void ConcurrentMarkSweepThread::trace_state(const char* desc) {
185 if (CMSTraceThreadState) {
186 char buf[128];
187 TimeStamp& ts = gclog_or_tty->time_stamp();
188 if (!ts.is_updated()) {
189 ts.update();
190 }
191 jio_snprintf(buf, sizeof(buf), " [%.3f: CMSThread %s] ",
192 ts.seconds(), desc);
193 buf[sizeof(buf) - 1] = '\0';
194 gclog_or_tty->print(buf);
195 }
196 }
197
198 // For scoped increment/decrement of yield requests
199 class CMSSynchronousYieldRequest: public StackObj {
200 public:
201 CMSSynchronousYieldRequest() {
202 ConcurrentMarkSweepThread::increment_pending_yields();
203 }
204 ~CMSSynchronousYieldRequest() {
205 ConcurrentMarkSweepThread::decrement_pending_yields();
206 }
207 };
208
209 // Used to emit a warning in case of unexpectedly excessive
210 // looping (in "apparently endless loops") in CMS code.
211 class CMSLoopCountWarn: public StackObj {
212 private:
213 const char* _src;
214 const char* _msg;
215 const intx _threshold;
216 intx _ticks;
217
218 public:
219 inline CMSLoopCountWarn(const char* src, const char* msg,
220 const intx threshold) :
221 _src(src), _msg(msg), _threshold(threshold), _ticks(0) { }
222
223 inline void tick() {
224 _ticks++;
225 if (CMSLoopWarn && _ticks % _threshold == 0) {
226 warning("%s has looped %d times %s", _src, _ticks, _msg);
227 }
228 }
229 };