1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp Sat Dec 01 00:00:00 2007 +0000
1.3 @@ -0,0 +1,229 @@
1.4 +/*
1.5 + * Copyright 2001-2006 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 +class ConcurrentMarkSweepGeneration;
1.29 +class CMSCollector;
1.30 +
1.31 +// The Concurrent Mark Sweep GC Thread (could be several in the future).
1.32 +class ConcurrentMarkSweepThread: public ConcurrentGCThread {
1.33 + friend class VMStructs;
1.34 + friend class ConcurrentMarkSweepGeneration; // XXX should remove friendship
1.35 + friend class CMSCollector;
1.36 + public:
1.37 + virtual void run();
1.38 +
1.39 + private:
1.40 + static ConcurrentMarkSweepThread* _cmst;
1.41 + static CMSCollector* _collector;
1.42 + static SurrogateLockerThread* _slt;
1.43 + static SurrogateLockerThread::SLT_msg_type _sltBuffer;
1.44 + static Monitor* _sltMonitor;
1.45 +
1.46 + ConcurrentMarkSweepThread* _next;
1.47 +
1.48 + static bool _should_terminate;
1.49 +
1.50 + enum CMS_flag_type {
1.51 + CMS_nil = NoBits,
1.52 + CMS_cms_wants_token = nth_bit(0),
1.53 + CMS_cms_has_token = nth_bit(1),
1.54 + CMS_vm_wants_token = nth_bit(2),
1.55 + CMS_vm_has_token = nth_bit(3)
1.56 + };
1.57 +
1.58 + static int _CMS_flag;
1.59 +
1.60 + static bool CMS_flag_is_set(int b) { return (_CMS_flag & b) != 0; }
1.61 + static bool set_CMS_flag(int b) { return (_CMS_flag |= b) != 0; }
1.62 + static bool clear_CMS_flag(int b) { return (_CMS_flag &= ~b) != 0; }
1.63 + void sleepBeforeNextCycle();
1.64 +
1.65 + // CMS thread should yield for a young gen collection, direct allocation,
1.66 + // and iCMS activity.
1.67 + static char _pad_1[64 - sizeof(jint)]; // prevent cache-line sharing
1.68 + static volatile jint _pending_yields;
1.69 + static volatile jint _pending_decrements; // decrements to _pending_yields
1.70 + static char _pad_2[64 - sizeof(jint)]; // prevent cache-line sharing
1.71 +
1.72 + // Tracing messages, enabled by CMSTraceThreadState.
1.73 + static inline void trace_state(const char* desc);
1.74 +
1.75 + static volatile bool _icms_enabled; // iCMS enabled?
1.76 + static volatile bool _should_run; // iCMS may run
1.77 + static volatile bool _should_stop; // iCMS should stop
1.78 +
1.79 + // debugging
1.80 + void verify_ok_to_terminate() const PRODUCT_RETURN;
1.81 +
1.82 + public:
1.83 + // Constructor
1.84 + ConcurrentMarkSweepThread(CMSCollector* collector);
1.85 +
1.86 + static void makeSurrogateLockerThread(TRAPS);
1.87 + static SurrogateLockerThread* slt() { return _slt; }
1.88 +
1.89 + // Tester
1.90 + bool is_ConcurrentGC_thread() const { return true; }
1.91 +
1.92 + static void threads_do(ThreadClosure* tc);
1.93 +
1.94 + // Printing
1.95 + void print_on(outputStream* st) const;
1.96 + void print() const { print_on(tty); }
1.97 + static void print_all_on(outputStream* st);
1.98 + static void print_all() { print_all_on(tty); }
1.99 +
1.100 + // Returns the CMS Thread
1.101 + static ConcurrentMarkSweepThread* cmst() { return _cmst; }
1.102 + static CMSCollector* collector() { return _collector; }
1.103 +
1.104 + // Create and start the CMS Thread, or stop it on shutdown
1.105 + static ConcurrentMarkSweepThread* start(CMSCollector* collector);
1.106 + static void stop();
1.107 + static bool should_terminate() { return _should_terminate; }
1.108 +
1.109 + // Synchronization using CMS token
1.110 + static void synchronize(bool is_cms_thread);
1.111 + static void desynchronize(bool is_cms_thread);
1.112 + static bool vm_thread_has_cms_token() {
1.113 + return CMS_flag_is_set(CMS_vm_has_token);
1.114 + }
1.115 + static bool cms_thread_has_cms_token() {
1.116 + return CMS_flag_is_set(CMS_cms_has_token);
1.117 + }
1.118 + static bool vm_thread_wants_cms_token() {
1.119 + return CMS_flag_is_set(CMS_vm_wants_token);
1.120 + }
1.121 + static bool cms_thread_wants_cms_token() {
1.122 + return CMS_flag_is_set(CMS_cms_wants_token);
1.123 + }
1.124 +
1.125 + // Wait on CMS lock until the next synchronous GC
1.126 + // or given timeout, whichever is earlier.
1.127 + void wait_on_cms_lock(long t); // milliseconds
1.128 +
1.129 + // The CMS thread will yield during the work portion of it's cycle
1.130 + // only when requested to. Both synchronous and asychronous requests
1.131 + // are provided. A synchronous request is used for young gen
1.132 + // collections and direct allocations. The requesting thread increments
1.133 + // pending_yields at the beginning of an operation, and decrements it when
1.134 + // the operation is completed. The CMS thread yields when pending_yields
1.135 + // is positive. An asynchronous request is used by iCMS in the stop_icms()
1.136 + // operation. A single yield satisfies the outstanding asynch yield requests.
1.137 + // The requesting thread increments both pending_yields and pending_decrements.
1.138 + // After yielding, the CMS thread decrements both by the amount in
1.139 + // pending_decrements.
1.140 + // Note that, while "_pending_yields >= _pending_decrements" is an invariant,
1.141 + // we cannot easily test that invariant, since the counters are manipulated via
1.142 + // atomic instructions without explicit locking and we cannot read
1.143 + // the two counters atomically together: one suggestion is to
1.144 + // use (for example) 16-bit counters so as to be able to read the
1.145 + // two counters atomically even on 32-bit platforms. Notice that
1.146 + // the second assert in acknowledge_yield_request() does indeed
1.147 + // check a form of the above invariant, albeit indirectly.
1.148 +
1.149 + static void increment_pending_yields() {
1.150 + Atomic::inc(&_pending_yields);
1.151 + assert(_pending_yields >= 0, "can't be negative");
1.152 + }
1.153 + static void decrement_pending_yields() {
1.154 + Atomic::dec(&_pending_yields);
1.155 + assert(_pending_yields >= 0, "can't be negative");
1.156 + }
1.157 + static void asynchronous_yield_request() {
1.158 + increment_pending_yields();
1.159 + Atomic::inc(&_pending_decrements);
1.160 + assert(_pending_decrements >= 0, "can't be negative");
1.161 + }
1.162 + static void acknowledge_yield_request() {
1.163 + jint decrement = _pending_decrements;
1.164 + if (decrement > 0) {
1.165 + // Order important to preserve: _pending_yields >= _pending_decrements
1.166 + Atomic::add(-decrement, &_pending_decrements);
1.167 + Atomic::add(-decrement, &_pending_yields);
1.168 + assert(_pending_decrements >= 0, "can't be negative");
1.169 + assert(_pending_yields >= 0, "can't be negative");
1.170 + }
1.171 + }
1.172 + static bool should_yield() { return _pending_yields > 0; }
1.173 +
1.174 + // CMS incremental mode.
1.175 + static void start_icms(); // notify thread to start a quantum of work
1.176 + static void stop_icms(); // request thread to stop working
1.177 + void icms_wait(); // if asked to stop, wait until notified to start
1.178 +
1.179 + // Incremental mode is enabled globally by the flag CMSIncrementalMode. It
1.180 + // must also be enabled/disabled dynamically to allow foreground collections.
1.181 + static inline void enable_icms() { _icms_enabled = true; }
1.182 + static inline void disable_icms() { _icms_enabled = false; }
1.183 + static inline void set_icms_enabled(bool val) { _icms_enabled = val; }
1.184 + static inline bool icms_enabled() { return _icms_enabled; }
1.185 +};
1.186 +
1.187 +inline void ConcurrentMarkSweepThread::trace_state(const char* desc) {
1.188 + if (CMSTraceThreadState) {
1.189 + char buf[128];
1.190 + TimeStamp& ts = gclog_or_tty->time_stamp();
1.191 + if (!ts.is_updated()) {
1.192 + ts.update();
1.193 + }
1.194 + jio_snprintf(buf, sizeof(buf), " [%.3f: CMSThread %s] ",
1.195 + ts.seconds(), desc);
1.196 + buf[sizeof(buf) - 1] = '\0';
1.197 + gclog_or_tty->print(buf);
1.198 + }
1.199 +}
1.200 +
1.201 +// For scoped increment/decrement of yield requests
1.202 +class CMSSynchronousYieldRequest: public StackObj {
1.203 + public:
1.204 + CMSSynchronousYieldRequest() {
1.205 + ConcurrentMarkSweepThread::increment_pending_yields();
1.206 + }
1.207 + ~CMSSynchronousYieldRequest() {
1.208 + ConcurrentMarkSweepThread::decrement_pending_yields();
1.209 + }
1.210 +};
1.211 +
1.212 +// Used to emit a warning in case of unexpectedly excessive
1.213 +// looping (in "apparently endless loops") in CMS code.
1.214 +class CMSLoopCountWarn: public StackObj {
1.215 + private:
1.216 + const char* _src;
1.217 + const char* _msg;
1.218 + const intx _threshold;
1.219 + intx _ticks;
1.220 +
1.221 + public:
1.222 + inline CMSLoopCountWarn(const char* src, const char* msg,
1.223 + const intx threshold) :
1.224 + _src(src), _msg(msg), _threshold(threshold), _ticks(0) { }
1.225 +
1.226 + inline void tick() {
1.227 + _ticks++;
1.228 + if (CMSLoopWarn && _ticks % _threshold == 0) {
1.229 + warning("%s has looped %d times %s", _src, _ticks, _msg);
1.230 + }
1.231 + }
1.232 +};
