1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/vm/runtime/safepoint.hpp Sat Dec 01 00:00:00 2007 +0000
1.3 @@ -0,0 +1,234 @@
1.4 +/*
1.5 + * Copyright 1997-2007 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 +//
1.29 +// Safepoint synchronization
1.30 +////
1.31 +// The VMThread or CMS_thread uses the SafepointSynchronize::begin/end
1.32 +// methods to enter/exit a safepoint region. The begin method will roll
1.33 +// all JavaThreads forward to a safepoint.
1.34 +//
1.35 +// JavaThreads must use the ThreadSafepointState abstraction (defined in
1.36 +// thread.hpp) to indicate that that they are at a safepoint.
1.37 +//
1.38 +// The Mutex/Condition variable and ObjectLocker classes calls the enter/
1.39 +// exit safepoint methods, when a thread is blocked/restarted. Hence, all mutex exter/
1.40 +// exit points *must* be at a safepoint.
1.41 +
1.42 +
1.43 +class ThreadSafepointState;
1.44 +class SnippetCache;
1.45 +class nmethod;
1.46 +
1.47 +//
1.48 +// Implements roll-forward to safepoint (safepoint synchronization)
1.49 +//
1.50 +class SafepointSynchronize : AllStatic {
1.51 + public:
1.52 + enum SynchronizeState {
1.53 + _not_synchronized = 0, // Threads not synchronized at a safepoint
1.54 + // Keep this value 0. See the coment in do_call_back()
1.55 + _synchronizing = 1, // Synchronizing in progress
1.56 + _synchronized = 2 // All Java threads are stopped at a safepoint. Only VM thread is running
1.57 + };
1.58 +
1.59 + enum SafepointingThread {
1.60 + _null_thread = 0,
1.61 + _vm_thread = 1,
1.62 + _other_thread = 2
1.63 + };
1.64 +
1.65 + enum SafepointTimeoutReason {
1.66 + _spinning_timeout = 0,
1.67 + _blocking_timeout = 1
1.68 + };
1.69 +
1.70 + typedef struct {
1.71 + int _vmop_type; // type of VM operation triggers the safepoint
1.72 + int _nof_total_threads; // total number of Java threads
1.73 + int _nof_initial_running_threads; // total number of initially seen running threads
1.74 + int _nof_threads_wait_to_block; // total number of threads waiting for to block
1.75 + bool _page_armed; // true if polling page is armed, false otherwise
1.76 + int _nof_threads_hit_page_trap; // total number of threads hitting the page trap
1.77 + jlong _time_to_spin; // total time in millis spent in spinning
1.78 + jlong _time_to_wait_to_block; // total time in millis spent in waiting for to block
1.79 + jlong _time_to_sync; // total time in millis spent in getting to _synchronized
1.80 + jlong _time_to_exec_vmop; // total time in millis spent in vm operation itself
1.81 + jlong _time_elapsed_since_last_safepoint; // time elasped since last safepoint
1.82 + } SafepointStats;
1.83 +
1.84 + private:
1.85 + static volatile SynchronizeState _state; // Threads might read this flag directly, without acquireing the Threads_lock
1.86 + static volatile int _waiting_to_block; // No. of threads we are waiting for to block.
1.87 +
1.88 + // This counter is used for fast versions of jni_Get<Primitive>Field.
1.89 + // An even value means there is no ongoing safepoint operations.
1.90 + // The counter is incremented ONLY at the beginning and end of each
1.91 + // safepoint. The fact that Threads_lock is held throughout each pair of
1.92 + // increments (at the beginning and end of each safepoint) guarantees
1.93 + // race freedom.
1.94 +public:
1.95 + static volatile int _safepoint_counter;
1.96 +private:
1.97 +
1.98 + static jlong _last_safepoint; // Time of last safepoint
1.99 +
1.100 + // statistics
1.101 + static SafepointStats* _safepoint_stats; // array of SafepointStats struct
1.102 + static int _cur_stat_index; // current index to the above array
1.103 + static julong _safepoint_reasons[]; // safepoint count for each VM op
1.104 + static julong _coalesced_vmop_count;// coalesced vmop count
1.105 + static jlong _max_sync_time; // maximum sync time in nanos
1.106 +
1.107 + static void begin_statistics(int nof_threads, int nof_running);
1.108 + static void update_statistics_on_spin_end();
1.109 + static void update_statistics_on_sync_end(jlong end_time);
1.110 + static void end_statistics(jlong end_time);
1.111 + static void print_statistics();
1.112 + inline static void inc_page_trap_count() {
1.113 + Atomic::inc(&_safepoint_stats[_cur_stat_index]._nof_threads_hit_page_trap);
1.114 + }
1.115 +
1.116 + // For debug long safepoint
1.117 + static void print_safepoint_timeout(SafepointTimeoutReason timeout_reason);
1.118 +
1.119 +public:
1.120 +
1.121 + // Main entry points
1.122 +
1.123 + // Roll all threads forward to safepoint. Must be called by the
1.124 + // VMThread or CMS_thread.
1.125 + static void begin();
1.126 + static void end(); // Start all suspended threads again...
1.127 +
1.128 + static bool safepoint_safe(JavaThread *thread, JavaThreadState state);
1.129 +
1.130 + // Query
1.131 + inline static bool is_at_safepoint() { return _state == _synchronized; }
1.132 + inline static bool is_synchronizing() { return _state == _synchronizing; }
1.133 +
1.134 + inline static bool do_call_back() {
1.135 + return (_state != _not_synchronized);
1.136 + }
1.137 +
1.138 + // Called when a thread volantary blocks
1.139 + static void block(JavaThread *thread);
1.140 + static void signal_thread_at_safepoint() { _waiting_to_block--; }
1.141 +
1.142 + // Exception handling for page polling
1.143 + static void handle_polling_page_exception(JavaThread *thread);
1.144 +
1.145 + // VM Thread interface for determining safepoint rate
1.146 + static long last_non_safepoint_interval() { return os::javaTimeMillis() - _last_safepoint; }
1.147 + static bool is_cleanup_needed();
1.148 + static void do_cleanup_tasks();
1.149 +
1.150 + // debugging
1.151 + static void print_state() PRODUCT_RETURN;
1.152 + static void safepoint_msg(const char* format, ...) PRODUCT_RETURN;
1.153 +
1.154 + static void deferred_initialize_stat();
1.155 + static void print_stat_on_exit();
1.156 + inline static void inc_vmop_coalesced_count() { _coalesced_vmop_count++; }
1.157 +
1.158 + static void set_is_at_safepoint() { _state = _synchronized; }
1.159 + static void set_is_not_at_safepoint() { _state = _not_synchronized; }
1.160 +
1.161 + // assembly support
1.162 + static address address_of_state() { return (address)&_state; }
1.163 +
1.164 + static address safepoint_counter_addr() { return (address)&_safepoint_counter; }
1.165 +};
1.166 +
1.167 +// State class for a thread suspended at a safepoint
1.168 +class ThreadSafepointState: public CHeapObj {
1.169 + public:
1.170 + // These states are maintained by VM thread while threads are being brought
1.171 + // to a safepoint. After SafepointSynchronize::end(), they are reset to
1.172 + // _running.
1.173 + enum suspend_type {
1.174 + _running = 0, // Thread state not yet determined (i.e., not at a safepoint yet)
1.175 + _at_safepoint = 1, // Thread at a safepoint (f.ex., when blocked on a lock)
1.176 + _call_back = 2 // Keep executing and wait for callback (if thread is in interpreted or vm)
1.177 + };
1.178 + private:
1.179 + volatile bool _at_poll_safepoint; // At polling page safepoint (NOT a poll return safepoint)
1.180 + // Thread has called back the safepoint code (for debugging)
1.181 + bool _has_called_back;
1.182 +
1.183 + JavaThread * _thread;
1.184 + volatile suspend_type _type;
1.185 +
1.186 +
1.187 + public:
1.188 + ThreadSafepointState(JavaThread *thread);
1.189 +
1.190 + // examine/roll-forward/restart
1.191 + void examine_state_of_thread();
1.192 + void roll_forward(suspend_type type);
1.193 + void restart();
1.194 +
1.195 + // Query
1.196 + JavaThread* thread() const { return _thread; }
1.197 + suspend_type type() const { return _type; }
1.198 + bool is_running() const { return (_type==_running); }
1.199 +
1.200 + // Support for safepoint timeout (debugging)
1.201 + bool has_called_back() const { return _has_called_back; }
1.202 + void set_has_called_back(bool val) { _has_called_back = val; }
1.203 + bool is_at_poll_safepoint() { return _at_poll_safepoint; }
1.204 + void set_at_poll_safepoint(bool val) { _at_poll_safepoint = val; }
1.205 +
1.206 + void handle_polling_page_exception();
1.207 +
1.208 + // debugging
1.209 + void print_on(outputStream* st) const;
1.210 + void print() const { print_on(tty); }
1.211 +
1.212 + // Initialize
1.213 + static void create(JavaThread *thread);
1.214 + static void destroy(JavaThread *thread);
1.215 +
1.216 + void safepoint_msg(const char* format, ...) {
1.217 + if (ShowSafepointMsgs) {
1.218 + va_list ap;
1.219 + va_start(ap, format);
1.220 + tty->vprint_cr(format, ap);
1.221 + va_end(ap);
1.222 + }
1.223 + }
1.224 +};
1.225 +
1.226 +//
1.227 +// CounterDecay
1.228 +//
1.229 +// Interates through invocation counters and decrements them. This
1.230 +// is done at each safepoint.
1.231 +//
1.232 +class CounterDecay : public AllStatic {
1.233 + static jlong _last_timestamp;
1.234 + public:
1.235 + static void decay();
1.236 + static bool is_decay_needed() { return (os::javaTimeMillis() - _last_timestamp) > CounterDecayMinIntervalLength; }
1.237 +};
