Mercurial > hg > graal-jvmci-8
diff src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp @ 0:a61af66fc99e jdk7-b24
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author | duke |
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date | Sat, 01 Dec 2007 00:00:00 +0000 |
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children | c18cbe5936b8 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp Sat Dec 01 00:00:00 2007 +0000 @@ -0,0 +1,229 @@ +/* + * Copyright 2001-2006 Sun Microsystems, Inc. All Rights Reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. + * + * This code is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + */ + +class ConcurrentMarkSweepGeneration; +class CMSCollector; + +// The Concurrent Mark Sweep GC Thread (could be several in the future). +class ConcurrentMarkSweepThread: public ConcurrentGCThread { + friend class VMStructs; + friend class ConcurrentMarkSweepGeneration; // XXX should remove friendship + friend class CMSCollector; + public: + virtual void run(); + + private: + static ConcurrentMarkSweepThread* _cmst; + static CMSCollector* _collector; + static SurrogateLockerThread* _slt; + static SurrogateLockerThread::SLT_msg_type _sltBuffer; + static Monitor* _sltMonitor; + + ConcurrentMarkSweepThread* _next; + + static bool _should_terminate; + + enum CMS_flag_type { + CMS_nil = NoBits, + CMS_cms_wants_token = nth_bit(0), + CMS_cms_has_token = nth_bit(1), + CMS_vm_wants_token = nth_bit(2), + CMS_vm_has_token = nth_bit(3) + }; + + static int _CMS_flag; + + static bool CMS_flag_is_set(int b) { return (_CMS_flag & b) != 0; } + static bool set_CMS_flag(int b) { return (_CMS_flag |= b) != 0; } + static bool clear_CMS_flag(int b) { return (_CMS_flag &= ~b) != 0; } + void sleepBeforeNextCycle(); + + // CMS thread should yield for a young gen collection, direct allocation, + // and iCMS activity. + static char _pad_1[64 - sizeof(jint)]; // prevent cache-line sharing + static volatile jint _pending_yields; + static volatile jint _pending_decrements; // decrements to _pending_yields + static char _pad_2[64 - sizeof(jint)]; // prevent cache-line sharing + + // Tracing messages, enabled by CMSTraceThreadState. + static inline void trace_state(const char* desc); + + static volatile bool _icms_enabled; // iCMS enabled? + static volatile bool _should_run; // iCMS may run + static volatile bool _should_stop; // iCMS should stop + + // debugging + void verify_ok_to_terminate() const PRODUCT_RETURN; + + public: + // Constructor + ConcurrentMarkSweepThread(CMSCollector* collector); + + static void makeSurrogateLockerThread(TRAPS); + static SurrogateLockerThread* slt() { return _slt; } + + // Tester + bool is_ConcurrentGC_thread() const { return true; } + + static void threads_do(ThreadClosure* tc); + + // Printing + void print_on(outputStream* st) const; + void print() const { print_on(tty); } + static void print_all_on(outputStream* st); + static void print_all() { print_all_on(tty); } + + // Returns the CMS Thread + static ConcurrentMarkSweepThread* cmst() { return _cmst; } + static CMSCollector* collector() { return _collector; } + + // Create and start the CMS Thread, or stop it on shutdown + static ConcurrentMarkSweepThread* start(CMSCollector* collector); + static void stop(); + static bool should_terminate() { return _should_terminate; } + + // Synchronization using CMS token + static void synchronize(bool is_cms_thread); + static void desynchronize(bool is_cms_thread); + static bool vm_thread_has_cms_token() { + return CMS_flag_is_set(CMS_vm_has_token); + } + static bool cms_thread_has_cms_token() { + return CMS_flag_is_set(CMS_cms_has_token); + } + static bool vm_thread_wants_cms_token() { + return CMS_flag_is_set(CMS_vm_wants_token); + } + static bool cms_thread_wants_cms_token() { + return CMS_flag_is_set(CMS_cms_wants_token); + } + + // Wait on CMS lock until the next synchronous GC + // or given timeout, whichever is earlier. + void wait_on_cms_lock(long t); // milliseconds + + // The CMS thread will yield during the work portion of it's cycle + // only when requested to. Both synchronous and asychronous requests + // are provided. A synchronous request is used for young gen + // collections and direct allocations. The requesting thread increments + // pending_yields at the beginning of an operation, and decrements it when + // the operation is completed. The CMS thread yields when pending_yields + // is positive. An asynchronous request is used by iCMS in the stop_icms() + // operation. A single yield satisfies the outstanding asynch yield requests. + // The requesting thread increments both pending_yields and pending_decrements. + // After yielding, the CMS thread decrements both by the amount in + // pending_decrements. + // Note that, while "_pending_yields >= _pending_decrements" is an invariant, + // we cannot easily test that invariant, since the counters are manipulated via + // atomic instructions without explicit locking and we cannot read + // the two counters atomically together: one suggestion is to + // use (for example) 16-bit counters so as to be able to read the + // two counters atomically even on 32-bit platforms. Notice that + // the second assert in acknowledge_yield_request() does indeed + // check a form of the above invariant, albeit indirectly. + + static void increment_pending_yields() { + Atomic::inc(&_pending_yields); + assert(_pending_yields >= 0, "can't be negative"); + } + static void decrement_pending_yields() { + Atomic::dec(&_pending_yields); + assert(_pending_yields >= 0, "can't be negative"); + } + static void asynchronous_yield_request() { + increment_pending_yields(); + Atomic::inc(&_pending_decrements); + assert(_pending_decrements >= 0, "can't be negative"); + } + static void acknowledge_yield_request() { + jint decrement = _pending_decrements; + if (decrement > 0) { + // Order important to preserve: _pending_yields >= _pending_decrements + Atomic::add(-decrement, &_pending_decrements); + Atomic::add(-decrement, &_pending_yields); + assert(_pending_decrements >= 0, "can't be negative"); + assert(_pending_yields >= 0, "can't be negative"); + } + } + static bool should_yield() { return _pending_yields > 0; } + + // CMS incremental mode. + static void start_icms(); // notify thread to start a quantum of work + static void stop_icms(); // request thread to stop working + void icms_wait(); // if asked to stop, wait until notified to start + + // Incremental mode is enabled globally by the flag CMSIncrementalMode. It + // must also be enabled/disabled dynamically to allow foreground collections. + static inline void enable_icms() { _icms_enabled = true; } + static inline void disable_icms() { _icms_enabled = false; } + static inline void set_icms_enabled(bool val) { _icms_enabled = val; } + static inline bool icms_enabled() { return _icms_enabled; } +}; + +inline void ConcurrentMarkSweepThread::trace_state(const char* desc) { + if (CMSTraceThreadState) { + char buf[128]; + TimeStamp& ts = gclog_or_tty->time_stamp(); + if (!ts.is_updated()) { + ts.update(); + } + jio_snprintf(buf, sizeof(buf), " [%.3f: CMSThread %s] ", + ts.seconds(), desc); + buf[sizeof(buf) - 1] = '\0'; + gclog_or_tty->print(buf); + } +} + +// For scoped increment/decrement of yield requests +class CMSSynchronousYieldRequest: public StackObj { + public: + CMSSynchronousYieldRequest() { + ConcurrentMarkSweepThread::increment_pending_yields(); + } + ~CMSSynchronousYieldRequest() { + ConcurrentMarkSweepThread::decrement_pending_yields(); + } +}; + +// Used to emit a warning in case of unexpectedly excessive +// looping (in "apparently endless loops") in CMS code. +class CMSLoopCountWarn: public StackObj { + private: + const char* _src; + const char* _msg; + const intx _threshold; + intx _ticks; + + public: + inline CMSLoopCountWarn(const char* src, const char* msg, + const intx threshold) : + _src(src), _msg(msg), _threshold(threshold), _ticks(0) { } + + inline void tick() { + _ticks++; + if (CMSLoopWarn && _ticks % _threshold == 0) { + warning("%s has looped %d times %s", _src, _ticks, _msg); + } + } +};