jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp@4947ee68d19c (annotated)

src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp@4947ee68d19c (annotated)

src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp

Thu, 06 Jan 2011 23:50:02 -0800

author: ysr
date: Thu, 06 Jan 2011 23:50:02 -0800
changeset 2452: 4947ee68d19c
parent 2314: f95d63e2154a
child 2647: a181f3a124dd
permissions: -rw-r--r--

7008136: CMS: assert((HeapWord*)nextChunk <= _limit) failed: sweep invariant
Summary: The recorded _sweep_limit may not necessarily remain a block boundary as the old generation expands during a concurrent cycle. Terminal actions inside the sweep closure need to be aware of this as they cross over the limit.
Reviewed-by: johnc, minqi

 /*
  * Copyright (c) 2001, 2010, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
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  */
 #ifndef SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPTHREAD_HPP
 #define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPTHREAD_HPP
 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.hpp"
 #include "gc_implementation/shared/concurrentGCThread.hpp"
 #ifdef TARGET_OS_FAMILY_linux
 # include "thread_linux.inline.hpp"
 #endif
 #ifdef TARGET_OS_FAMILY_solaris
 # include "thread_solaris.inline.hpp"
 #endif
 #ifdef TARGET_OS_FAMILY_windows
 # include "thread_windows.inline.hpp"
 #endif
 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. A timeout value
   // of 0 indicates that there is no upper bound on the wait time.
   // A concurrent full gc request terminates the wait.
   void wait_on_cms_lock(long t_millis);
   // The CMS thread will yield during the work portion of its cycle
   // only when requested to.  Both synchronous and asychronous requests
   // are provided:
   // (1) A synchronous request is used for young gen collections and
   //     for direct allocations.  The requesting thread increments
   //     _pending_yields at the beginning of an operation, and decrements
   //     _pending_yields when that operation is completed.
   //     In turn, the CMS thread yields when _pending_yields is positive,
   //     and continues to yield until the value reverts to 0.
   // (2) An asynchronous request, on the other hand, is used by iCMS
   //     for the stop_icms() operation. A single yield satisfies all of
   //     the outstanding asynch yield requests, of which there may
   //     occasionally be several in close succession. To accomplish
   //     this, an asynch-requesting thread atomically increments both
   //     _pending_yields and _pending_decrements. An asynchr requesting
   //     thread does not wait and "acknowledge" completion of an operation
   //     and deregister the request, like the synchronous version described
   //     above does. In turn, after yielding, the CMS thread decrements both
   //     _pending_yields and _pending_decrements by the value seen in
   //     _pending_decrements before the decrement.
   //  NOTE: The above scheme is isomorphic to having two request counters,
   //  one for async requests and one for sync requests, and for the CMS thread
   //  to check the sum of the two counters to decide whether it should yield
   //  and to clear only the async counter when it yields. However, it turns out
   //  to be more efficient for CMS code to just check a single counter
   //  _pending_yields that holds the sum (of both sync and async requests), and
   //  a second counter _pending_decrements that only holds the async requests,
   //  for greater efficiency, since in a typical CMS run, there are many more
   //  pontential (i.e. static) yield points than there are actual
   //  (i.e. dynamic) yields because of requests, which are few and far between.
   //
   // 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() below 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() {
     assert(CMSIncrementalMode, "Currently only used w/iCMS");
     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) {
       assert(CMSIncrementalMode, "Currently only used w/iCMS");
       // 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 (synchronous) 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);
     }
   }
 };
 #endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_CONCURRENTMARKSWEEPTHREAD_HPP

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp@4947ee68d19c (annotated)

src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp