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src/share/vm/runtime/safepoint.hpp@9f4457a14b58 (annotated)

src/share/vm/runtime/safepoint.hpp

Wed, 09 Apr 2008 15:10:22 -0700

author

rasbold

date

Wed, 09 Apr 2008 15:10:22 -0700

changeset 544

9f4457a14b58

parent 435

a61af66fc99e

child 1726

4b0f2f4918ed

permissions

-rw-r--r--

Merge

duke@435	1	/*
duke@435	2	* Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved.
duke@435	3	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435	4	*
duke@435	5	* This code is free software; you can redistribute it and/or modify it
duke@435	6	* under the terms of the GNU General Public License version 2 only, as
duke@435	7	* published by the Free Software Foundation.
duke@435	8	*
duke@435	9	* This code is distributed in the hope that it will be useful, but WITHOUT
duke@435	10	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435	11	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
duke@435	12	* version 2 for more details (a copy is included in the LICENSE file that
duke@435	13	* accompanied this code).
duke@435	14	*
duke@435	15	* You should have received a copy of the GNU General Public License version
duke@435	16	* 2 along with this work; if not, write to the Free Software Foundation,
duke@435	17	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435	18	*
duke@435	19	* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
duke@435	20	* CA 95054 USA or visit www.sun.com if you need additional information or
duke@435	21	* have any questions.
duke@435	22	*
duke@435	23	*/
duke@435	24
duke@435	25	//
duke@435	26	// Safepoint synchronization
duke@435	27	////
duke@435	28	// The VMThread or CMS_thread uses the SafepointSynchronize::begin/end
duke@435	29	// methods to enter/exit a safepoint region. The begin method will roll
duke@435	30	// all JavaThreads forward to a safepoint.
duke@435	31	//
duke@435	32	// JavaThreads must use the ThreadSafepointState abstraction (defined in
duke@435	33	// thread.hpp) to indicate that that they are at a safepoint.
duke@435	34	//
duke@435	35	// The Mutex/Condition variable and ObjectLocker classes calls the enter/
duke@435	36	// exit safepoint methods, when a thread is blocked/restarted. Hence, all mutex exter/
duke@435	37	// exit points *must* be at a safepoint.
duke@435	38
duke@435	39
duke@435	40	class ThreadSafepointState;
duke@435	41	class SnippetCache;
duke@435	42	class nmethod;
duke@435	43
duke@435	44	//
duke@435	45	// Implements roll-forward to safepoint (safepoint synchronization)
duke@435	46	//
duke@435	47	class SafepointSynchronize : AllStatic {
duke@435	48	public:
duke@435	49	enum SynchronizeState {
duke@435	50	_not_synchronized = 0, // Threads not synchronized at a safepoint
duke@435	51	// Keep this value 0. See the coment in do_call_back()
duke@435	52	_synchronizing = 1, // Synchronizing in progress
duke@435	53	_synchronized = 2 // All Java threads are stopped at a safepoint. Only VM thread is running
duke@435	54	};
duke@435	55
duke@435	56	enum SafepointingThread {
duke@435	57	_null_thread = 0,
duke@435	58	_vm_thread = 1,
duke@435	59	_other_thread = 2
duke@435	60	};
duke@435	61
duke@435	62	enum SafepointTimeoutReason {
duke@435	63	_spinning_timeout = 0,
duke@435	64	_blocking_timeout = 1
duke@435	65	};
duke@435	66
duke@435	67	typedef struct {
duke@435	68	int _vmop_type; // type of VM operation triggers the safepoint
duke@435	69	int _nof_total_threads; // total number of Java threads
duke@435	70	int _nof_initial_running_threads; // total number of initially seen running threads
duke@435	71	int _nof_threads_wait_to_block; // total number of threads waiting for to block
duke@435	72	bool _page_armed; // true if polling page is armed, false otherwise
duke@435	73	int _nof_threads_hit_page_trap; // total number of threads hitting the page trap
duke@435	74	jlong _time_to_spin; // total time in millis spent in spinning
duke@435	75	jlong _time_to_wait_to_block; // total time in millis spent in waiting for to block
duke@435	76	jlong _time_to_sync; // total time in millis spent in getting to _synchronized
duke@435	77	jlong _time_to_exec_vmop; // total time in millis spent in vm operation itself
duke@435	78	jlong _time_elapsed_since_last_safepoint; // time elasped since last safepoint
duke@435	79	} SafepointStats;
duke@435	80
duke@435	81	private:
duke@435	82	static volatile SynchronizeState _state; // Threads might read this flag directly, without acquireing the Threads_lock
duke@435	83	static volatile int _waiting_to_block; // No. of threads we are waiting for to block.
duke@435	84
duke@435	85	// This counter is used for fast versions of jni_Get<Primitive>Field.
duke@435	86	// An even value means there is no ongoing safepoint operations.
duke@435	87	// The counter is incremented ONLY at the beginning and end of each
duke@435	88	// safepoint. The fact that Threads_lock is held throughout each pair of
duke@435	89	// increments (at the beginning and end of each safepoint) guarantees
duke@435	90	// race freedom.
duke@435	91	public:
duke@435	92	static volatile int _safepoint_counter;
duke@435	93	private:
duke@435	94
duke@435	95	static jlong _last_safepoint; // Time of last safepoint
duke@435	96
duke@435	97	// statistics
duke@435	98	static SafepointStats* _safepoint_stats; // array of SafepointStats struct
duke@435	99	static int _cur_stat_index; // current index to the above array
duke@435	100	static julong _safepoint_reasons[]; // safepoint count for each VM op
duke@435	101	static julong _coalesced_vmop_count;// coalesced vmop count
duke@435	102	static jlong _max_sync_time; // maximum sync time in nanos
duke@435	103
duke@435	104	static void begin_statistics(int nof_threads, int nof_running);
duke@435	105	static void update_statistics_on_spin_end();
duke@435	106	static void update_statistics_on_sync_end(jlong end_time);
duke@435	107	static void end_statistics(jlong end_time);
duke@435	108	static void print_statistics();
duke@435	109	inline static void inc_page_trap_count() {
duke@435	110	Atomic::inc(&_safepoint_stats[_cur_stat_index]._nof_threads_hit_page_trap);
duke@435	111	}
duke@435	112
duke@435	113	// For debug long safepoint
duke@435	114	static void print_safepoint_timeout(SafepointTimeoutReason timeout_reason);
duke@435	115
duke@435	116	public:
duke@435	117
duke@435	118	// Main entry points
duke@435	119
duke@435	120	// Roll all threads forward to safepoint. Must be called by the
duke@435	121	// VMThread or CMS_thread.
duke@435	122	static void begin();
duke@435	123	static void end(); // Start all suspended threads again...
duke@435	124
duke@435	125	static bool safepoint_safe(JavaThread *thread, JavaThreadState state);
duke@435	126
duke@435	127	// Query
duke@435	128	inline static bool is_at_safepoint() { return _state == _synchronized; }
duke@435	129	inline static bool is_synchronizing() { return _state == _synchronizing; }
duke@435	130
duke@435	131	inline static bool do_call_back() {
duke@435	132	return (_state != _not_synchronized);
duke@435	133	}
duke@435	134
duke@435	135	// Called when a thread volantary blocks
duke@435	136	static void block(JavaThread *thread);
duke@435	137	static void signal_thread_at_safepoint() { _waiting_to_block--; }
duke@435	138
duke@435	139	// Exception handling for page polling
duke@435	140	static void handle_polling_page_exception(JavaThread *thread);
duke@435	141
duke@435	142	// VM Thread interface for determining safepoint rate
duke@435	143	static long last_non_safepoint_interval() { return os::javaTimeMillis() - _last_safepoint; }
duke@435	144	static bool is_cleanup_needed();
duke@435	145	static void do_cleanup_tasks();
duke@435	146
duke@435	147	// debugging
duke@435	148	static void print_state() PRODUCT_RETURN;
duke@435	149	static void safepoint_msg(const char* format, ...) PRODUCT_RETURN;
duke@435	150
duke@435	151	static void deferred_initialize_stat();
duke@435	152	static void print_stat_on_exit();
duke@435	153	inline static void inc_vmop_coalesced_count() { _coalesced_vmop_count++; }
duke@435	154
duke@435	155	static void set_is_at_safepoint() { _state = _synchronized; }
duke@435	156	static void set_is_not_at_safepoint() { _state = _not_synchronized; }
duke@435	157
duke@435	158	// assembly support
duke@435	159	static address address_of_state() { return (address)&_state; }
duke@435	160
duke@435	161	static address safepoint_counter_addr() { return (address)&_safepoint_counter; }
duke@435	162	};
duke@435	163
duke@435	164	// State class for a thread suspended at a safepoint
duke@435	165	class ThreadSafepointState: public CHeapObj {
duke@435	166	public:
duke@435	167	// These states are maintained by VM thread while threads are being brought
duke@435	168	// to a safepoint. After SafepointSynchronize::end(), they are reset to
duke@435	169	// _running.
duke@435	170	enum suspend_type {
duke@435	171	_running = 0, // Thread state not yet determined (i.e., not at a safepoint yet)
duke@435	172	_at_safepoint = 1, // Thread at a safepoint (f.ex., when blocked on a lock)
duke@435	173	_call_back = 2 // Keep executing and wait for callback (if thread is in interpreted or vm)
duke@435	174	};
duke@435	175	private:
duke@435	176	volatile bool _at_poll_safepoint; // At polling page safepoint (NOT a poll return safepoint)
duke@435	177	// Thread has called back the safepoint code (for debugging)
duke@435	178	bool _has_called_back;
duke@435	179
duke@435	180	JavaThread * _thread;
duke@435	181	volatile suspend_type _type;
duke@435	182
duke@435	183
duke@435	184	public:
duke@435	185	ThreadSafepointState(JavaThread *thread);
duke@435	186
duke@435	187	// examine/roll-forward/restart
duke@435	188	void examine_state_of_thread();
duke@435	189	void roll_forward(suspend_type type);
duke@435	190	void restart();
duke@435	191
duke@435	192	// Query
duke@435	193	JavaThread* thread() const { return _thread; }
duke@435	194	suspend_type type() const { return _type; }
duke@435	195	bool is_running() const { return (_type==_running); }
duke@435	196
duke@435	197	// Support for safepoint timeout (debugging)
duke@435	198	bool has_called_back() const { return _has_called_back; }
duke@435	199	void set_has_called_back(bool val) { _has_called_back = val; }
duke@435	200	bool is_at_poll_safepoint() { return _at_poll_safepoint; }
duke@435	201	void set_at_poll_safepoint(bool val) { _at_poll_safepoint = val; }
duke@435	202
duke@435	203	void handle_polling_page_exception();
duke@435	204
duke@435	205	// debugging
duke@435	206	void print_on(outputStream* st) const;
duke@435	207	void print() const { print_on(tty); }
duke@435	208
duke@435	209	// Initialize
duke@435	210	static void create(JavaThread *thread);
duke@435	211	static void destroy(JavaThread *thread);
duke@435	212
duke@435	213	void safepoint_msg(const char* format, ...) {
duke@435	214	if (ShowSafepointMsgs) {
duke@435	215	va_list ap;
duke@435	216	va_start(ap, format);
duke@435	217	tty->vprint_cr(format, ap);
duke@435	218	va_end(ap);
duke@435	219	}
duke@435	220	}
duke@435	221	};
duke@435	222
duke@435	223	//
duke@435	224	// CounterDecay
duke@435	225	//
duke@435	226	// Interates through invocation counters and decrements them. This
duke@435	227	// is done at each safepoint.
duke@435	228	//
duke@435	229	class CounterDecay : public AllStatic {
duke@435	230	static jlong _last_timestamp;
duke@435	231	public:
duke@435	232	static void decay();
duke@435	233	static bool is_decay_needed() { return (os::javaTimeMillis() - _last_timestamp) > CounterDecayMinIntervalLength; }
duke@435	234	};