1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.cpp Wed Apr 27 01:25:04 2016 +0800
1.3 @@ -0,0 +1,469 @@
1.4 +/*
1.5 + * Copyright (c) 2001, 2014, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.23 + * or visit www.oracle.com if you need additional information or have any
1.24 + * questions.
1.25 + *
1.26 + */
1.27 +
1.28 +#include "precompiled.hpp"
1.29 +#include "classfile/systemDictionary.hpp"
1.30 +#include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp"
1.31 +#include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
1.32 +#include "memory/genCollectedHeap.hpp"
1.33 +#include "oops/instanceRefKlass.hpp"
1.34 +#include "oops/oop.inline.hpp"
1.35 +#include "runtime/init.hpp"
1.36 +#include "runtime/interfaceSupport.hpp"
1.37 +#include "runtime/java.hpp"
1.38 +#include "runtime/javaCalls.hpp"
1.39 +#include "runtime/mutexLocker.hpp"
1.40 +#include "runtime/os.hpp"
1.41 +#include "runtime/vmThread.hpp"
1.42 +
1.43 +// ======= Concurrent Mark Sweep Thread ========
1.44 +
1.45 +// The CMS thread is created when Concurrent Mark Sweep is used in the
1.46 +// older of two generations in a generational memory system.
1.47 +
1.48 +ConcurrentMarkSweepThread*
1.49 + ConcurrentMarkSweepThread::_cmst = NULL;
1.50 +CMSCollector* ConcurrentMarkSweepThread::_collector = NULL;
1.51 +bool ConcurrentMarkSweepThread::_should_terminate = false;
1.52 +int ConcurrentMarkSweepThread::_CMS_flag = CMS_nil;
1.53 +
1.54 +volatile jint ConcurrentMarkSweepThread::_pending_yields = 0;
1.55 +volatile jint ConcurrentMarkSweepThread::_pending_decrements = 0;
1.56 +
1.57 +volatile jint ConcurrentMarkSweepThread::_icms_disabled = 0;
1.58 +volatile bool ConcurrentMarkSweepThread::_should_run = false;
1.59 +// When icms is enabled, the icms thread is stopped until explicitly
1.60 +// started.
1.61 +volatile bool ConcurrentMarkSweepThread::_should_stop = true;
1.62 +
1.63 +SurrogateLockerThread*
1.64 + ConcurrentMarkSweepThread::_slt = NULL;
1.65 +SurrogateLockerThread::SLT_msg_type
1.66 + ConcurrentMarkSweepThread::_sltBuffer = SurrogateLockerThread::empty;
1.67 +Monitor*
1.68 + ConcurrentMarkSweepThread::_sltMonitor = NULL;
1.69 +
1.70 +ConcurrentMarkSweepThread::ConcurrentMarkSweepThread(CMSCollector* collector)
1.71 + : ConcurrentGCThread() {
1.72 + assert(UseConcMarkSweepGC, "UseConcMarkSweepGC should be set");
1.73 + assert(_cmst == NULL, "CMS thread already created");
1.74 + _cmst = this;
1.75 + assert(_collector == NULL, "Collector already set");
1.76 + _collector = collector;
1.77 +
1.78 + set_name("Concurrent Mark-Sweep GC Thread");
1.79 +
1.80 + if (os::create_thread(this, os::cgc_thread)) {
1.81 + // An old comment here said: "Priority should be just less
1.82 + // than that of VMThread". Since the VMThread runs at
1.83 + // NearMaxPriority, the old comment was inaccurate, but
1.84 + // changing the default priority to NearMaxPriority-1
1.85 + // could change current behavior, so the default of
1.86 + // NearMaxPriority stays in place.
1.87 + //
1.88 + // Note that there's a possibility of the VMThread
1.89 + // starving if UseCriticalCMSThreadPriority is on.
1.90 + // That won't happen on Solaris for various reasons,
1.91 + // but may well happen on non-Solaris platforms.
1.92 + int native_prio;
1.93 + if (UseCriticalCMSThreadPriority) {
1.94 + native_prio = os::java_to_os_priority[CriticalPriority];
1.95 + } else {
1.96 + native_prio = os::java_to_os_priority[NearMaxPriority];
1.97 + }
1.98 + os::set_native_priority(this, native_prio);
1.99 +
1.100 + if (!DisableStartThread) {
1.101 + os::start_thread(this);
1.102 + }
1.103 + }
1.104 + _sltMonitor = SLT_lock;
1.105 + assert(!CMSIncrementalMode || icms_is_enabled(), "Error");
1.106 +}
1.107 +
1.108 +void ConcurrentMarkSweepThread::run() {
1.109 + assert(this == cmst(), "just checking");
1.110 +
1.111 + this->record_stack_base_and_size();
1.112 + this->initialize_thread_local_storage();
1.113 + this->set_active_handles(JNIHandleBlock::allocate_block());
1.114 + // From this time Thread::current() should be working.
1.115 + assert(this == Thread::current(), "just checking");
1.116 + if (BindCMSThreadToCPU && !os::bind_to_processor(CPUForCMSThread)) {
1.117 + warning("Couldn't bind CMS thread to processor " UINTX_FORMAT, CPUForCMSThread);
1.118 + }
1.119 + // Wait until Universe::is_fully_initialized()
1.120 + {
1.121 + CMSLoopCountWarn loopX("CMS::run", "waiting for "
1.122 + "Universe::is_fully_initialized()", 2);
1.123 + MutexLockerEx x(CGC_lock, true);
1.124 + set_CMS_flag(CMS_cms_wants_token);
1.125 + // Wait until Universe is initialized and all initialization is completed.
1.126 + while (!is_init_completed() && !Universe::is_fully_initialized() &&
1.127 + !_should_terminate) {
1.128 + CGC_lock->wait(true, 200);
1.129 + loopX.tick();
1.130 + }
1.131 + // Wait until the surrogate locker thread that will do
1.132 + // pending list locking on our behalf has been created.
1.133 + // We cannot start the SLT thread ourselves since we need
1.134 + // to be a JavaThread to do so.
1.135 + CMSLoopCountWarn loopY("CMS::run", "waiting for SLT installation", 2);
1.136 + while (_slt == NULL && !_should_terminate) {
1.137 + CGC_lock->wait(true, 200);
1.138 + loopY.tick();
1.139 + }
1.140 + clear_CMS_flag(CMS_cms_wants_token);
1.141 + }
1.142 +
1.143 + while (!_should_terminate) {
1.144 + sleepBeforeNextCycle();
1.145 + if (_should_terminate) break;
1.146 + GCCause::Cause cause = _collector->_full_gc_requested ?
1.147 + _collector->_full_gc_cause : GCCause::_cms_concurrent_mark;
1.148 + _collector->collect_in_background(false, cause);
1.149 + }
1.150 + assert(_should_terminate, "just checking");
1.151 + // Check that the state of any protocol for synchronization
1.152 + // between background (CMS) and foreground collector is "clean"
1.153 + // (i.e. will not potentially block the foreground collector,
1.154 + // requiring action by us).
1.155 + verify_ok_to_terminate();
1.156 + // Signal that it is terminated
1.157 + {
1.158 + MutexLockerEx mu(Terminator_lock,
1.159 + Mutex::_no_safepoint_check_flag);
1.160 + assert(_cmst == this, "Weird!");
1.161 + _cmst = NULL;
1.162 + Terminator_lock->notify();
1.163 + }
1.164 +
1.165 + // Thread destructor usually does this..
1.166 + ThreadLocalStorage::set_thread(NULL);
1.167 +}
1.168 +
1.169 +#ifndef PRODUCT
1.170 +void ConcurrentMarkSweepThread::verify_ok_to_terminate() const {
1.171 + assert(!(CGC_lock->owned_by_self() || cms_thread_has_cms_token() ||
1.172 + cms_thread_wants_cms_token()),
1.173 + "Must renounce all worldly possessions and desires for nirvana");
1.174 + _collector->verify_ok_to_terminate();
1.175 +}
1.176 +#endif
1.177 +
1.178 +// create and start a new ConcurrentMarkSweep Thread for given CMS generation
1.179 +ConcurrentMarkSweepThread* ConcurrentMarkSweepThread::start(CMSCollector* collector) {
1.180 + if (!_should_terminate) {
1.181 + assert(cmst() == NULL, "start() called twice?");
1.182 + ConcurrentMarkSweepThread* th = new ConcurrentMarkSweepThread(collector);
1.183 + assert(cmst() == th, "Where did the just-created CMS thread go?");
1.184 + return th;
1.185 + }
1.186 + return NULL;
1.187 +}
1.188 +
1.189 +void ConcurrentMarkSweepThread::stop() {
1.190 + if (CMSIncrementalMode) {
1.191 + // Disable incremental mode and wake up the thread so it notices the change.
1.192 + disable_icms();
1.193 + start_icms();
1.194 + }
1.195 + // it is ok to take late safepoints here, if needed
1.196 + {
1.197 + MutexLockerEx x(Terminator_lock);
1.198 + _should_terminate = true;
1.199 + }
1.200 + { // Now post a notify on CGC_lock so as to nudge
1.201 + // CMS thread(s) that might be slumbering in
1.202 + // sleepBeforeNextCycle.
1.203 + MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
1.204 + CGC_lock->notify_all();
1.205 + }
1.206 + { // Now wait until (all) CMS thread(s) have exited
1.207 + MutexLockerEx x(Terminator_lock);
1.208 + while(cmst() != NULL) {
1.209 + Terminator_lock->wait();
1.210 + }
1.211 + }
1.212 +}
1.213 +
1.214 +void ConcurrentMarkSweepThread::threads_do(ThreadClosure* tc) {
1.215 + assert(tc != NULL, "Null ThreadClosure");
1.216 + if (_cmst != NULL) {
1.217 + tc->do_thread(_cmst);
1.218 + }
1.219 + assert(Universe::is_fully_initialized(),
1.220 + "Called too early, make sure heap is fully initialized");
1.221 + if (_collector != NULL) {
1.222 + AbstractWorkGang* gang = _collector->conc_workers();
1.223 + if (gang != NULL) {
1.224 + gang->threads_do(tc);
1.225 + }
1.226 + }
1.227 +}
1.228 +
1.229 +void ConcurrentMarkSweepThread::print_on(outputStream* st) const {
1.230 + st->print("\"%s\" ", name());
1.231 + Thread::print_on(st);
1.232 + st->cr();
1.233 +}
1.234 +
1.235 +void ConcurrentMarkSweepThread::print_all_on(outputStream* st) {
1.236 + if (_cmst != NULL) {
1.237 + _cmst->print_on(st);
1.238 + st->cr();
1.239 + }
1.240 + if (_collector != NULL) {
1.241 + AbstractWorkGang* gang = _collector->conc_workers();
1.242 + if (gang != NULL) {
1.243 + gang->print_worker_threads_on(st);
1.244 + }
1.245 + }
1.246 +}
1.247 +
1.248 +void ConcurrentMarkSweepThread::synchronize(bool is_cms_thread) {
1.249 + assert(UseConcMarkSweepGC, "just checking");
1.250 +
1.251 + MutexLockerEx x(CGC_lock,
1.252 + Mutex::_no_safepoint_check_flag);
1.253 + if (!is_cms_thread) {
1.254 + assert(Thread::current()->is_VM_thread(), "Not a VM thread");
1.255 + CMSSynchronousYieldRequest yr;
1.256 + while (CMS_flag_is_set(CMS_cms_has_token)) {
1.257 + // indicate that we want to get the token
1.258 + set_CMS_flag(CMS_vm_wants_token);
1.259 + CGC_lock->wait(true);
1.260 + }
1.261 + // claim the token and proceed
1.262 + clear_CMS_flag(CMS_vm_wants_token);
1.263 + set_CMS_flag(CMS_vm_has_token);
1.264 + } else {
1.265 + assert(Thread::current()->is_ConcurrentGC_thread(),
1.266 + "Not a CMS thread");
1.267 + // The following barrier assumes there's only one CMS thread.
1.268 + // This will need to be modified is there are more CMS threads than one.
1.269 + while (CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token)) {
1.270 + set_CMS_flag(CMS_cms_wants_token);
1.271 + CGC_lock->wait(true);
1.272 + }
1.273 + // claim the token
1.274 + clear_CMS_flag(CMS_cms_wants_token);
1.275 + set_CMS_flag(CMS_cms_has_token);
1.276 + }
1.277 +}
1.278 +
1.279 +void ConcurrentMarkSweepThread::desynchronize(bool is_cms_thread) {
1.280 + assert(UseConcMarkSweepGC, "just checking");
1.281 +
1.282 + MutexLockerEx x(CGC_lock,
1.283 + Mutex::_no_safepoint_check_flag);
1.284 + if (!is_cms_thread) {
1.285 + assert(Thread::current()->is_VM_thread(), "Not a VM thread");
1.286 + assert(CMS_flag_is_set(CMS_vm_has_token), "just checking");
1.287 + clear_CMS_flag(CMS_vm_has_token);
1.288 + if (CMS_flag_is_set(CMS_cms_wants_token)) {
1.289 + // wake-up a waiting CMS thread
1.290 + CGC_lock->notify();
1.291 + }
1.292 + assert(!CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token),
1.293 + "Should have been cleared");
1.294 + } else {
1.295 + assert(Thread::current()->is_ConcurrentGC_thread(),
1.296 + "Not a CMS thread");
1.297 + assert(CMS_flag_is_set(CMS_cms_has_token), "just checking");
1.298 + clear_CMS_flag(CMS_cms_has_token);
1.299 + if (CMS_flag_is_set(CMS_vm_wants_token)) {
1.300 + // wake-up a waiting VM thread
1.301 + CGC_lock->notify();
1.302 + }
1.303 + assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
1.304 + "Should have been cleared");
1.305 + }
1.306 +}
1.307 +
1.308 +// Wait until any cms_lock event
1.309 +void ConcurrentMarkSweepThread::wait_on_cms_lock(long t_millis) {
1.310 + MutexLockerEx x(CGC_lock,
1.311 + Mutex::_no_safepoint_check_flag);
1.312 + if (_should_terminate || _collector->_full_gc_requested) {
1.313 + return;
1.314 + }
1.315 + set_CMS_flag(CMS_cms_wants_token); // to provoke notifies
1.316 + CGC_lock->wait(Mutex::_no_safepoint_check_flag, t_millis);
1.317 + clear_CMS_flag(CMS_cms_wants_token);
1.318 + assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
1.319 + "Should not be set");
1.320 +}
1.321 +
1.322 +// Wait until the next synchronous GC, a concurrent full gc request,
1.323 +// or a timeout, whichever is earlier.
1.324 +void ConcurrentMarkSweepThread::wait_on_cms_lock_for_scavenge(long t_millis) {
1.325 + // Wait time in millis or 0 value representing infinite wait for a scavenge
1.326 + assert(t_millis >= 0, "Wait time for scavenge should be 0 or positive");
1.327 +
1.328 + GenCollectedHeap* gch = GenCollectedHeap::heap();
1.329 + double start_time_secs = os::elapsedTime();
1.330 + double end_time_secs = start_time_secs + (t_millis / ((double) MILLIUNITS));
1.331 +
1.332 + // Total collections count before waiting loop
1.333 + unsigned int before_count;
1.334 + {
1.335 + MutexLockerEx hl(Heap_lock, Mutex::_no_safepoint_check_flag);
1.336 + before_count = gch->total_collections();
1.337 + }
1.338 +
1.339 + unsigned int loop_count = 0;
1.340 +
1.341 + while(!_should_terminate) {
1.342 + double now_time = os::elapsedTime();
1.343 + long wait_time_millis;
1.344 +
1.345 + if(t_millis != 0) {
1.346 + // New wait limit
1.347 + wait_time_millis = (long) ((end_time_secs - now_time) * MILLIUNITS);
1.348 + if(wait_time_millis <= 0) {
1.349 + // Wait time is over
1.350 + break;
1.351 + }
1.352 + } else {
1.353 + // No wait limit, wait if necessary forever
1.354 + wait_time_millis = 0;
1.355 + }
1.356 +
1.357 + // Wait until the next event or the remaining timeout
1.358 + {
1.359 + MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
1.360 +
1.361 + if (_should_terminate || _collector->_full_gc_requested) {
1.362 + return;
1.363 + }
1.364 + set_CMS_flag(CMS_cms_wants_token); // to provoke notifies
1.365 + assert(t_millis == 0 || wait_time_millis > 0, "Sanity");
1.366 + CGC_lock->wait(Mutex::_no_safepoint_check_flag, wait_time_millis);
1.367 + clear_CMS_flag(CMS_cms_wants_token);
1.368 + assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
1.369 + "Should not be set");
1.370 + }
1.371 +
1.372 + // Extra wait time check before entering the heap lock to get the collection count
1.373 + if(t_millis != 0 && os::elapsedTime() >= end_time_secs) {
1.374 + // Wait time is over
1.375 + break;
1.376 + }
1.377 +
1.378 + // Total collections count after the event
1.379 + unsigned int after_count;
1.380 + {
1.381 + MutexLockerEx hl(Heap_lock, Mutex::_no_safepoint_check_flag);
1.382 + after_count = gch->total_collections();
1.383 + }
1.384 +
1.385 + if(before_count != after_count) {
1.386 + // There was a collection - success
1.387 + break;
1.388 + }
1.389 +
1.390 + // Too many loops warning
1.391 + if(++loop_count == 0) {
1.392 + warning("wait_on_cms_lock_for_scavenge() has looped %u times", loop_count - 1);
1.393 + }
1.394 + }
1.395 +}
1.396 +
1.397 +void ConcurrentMarkSweepThread::sleepBeforeNextCycle() {
1.398 + while (!_should_terminate) {
1.399 + if (CMSIncrementalMode) {
1.400 + icms_wait();
1.401 + if(CMSWaitDuration >= 0) {
1.402 + // Wait until the next synchronous GC, a concurrent full gc
1.403 + // request or a timeout, whichever is earlier.
1.404 + wait_on_cms_lock_for_scavenge(CMSWaitDuration);
1.405 + }
1.406 + return;
1.407 + } else {
1.408 + if(CMSWaitDuration >= 0) {
1.409 + // Wait until the next synchronous GC, a concurrent full gc
1.410 + // request or a timeout, whichever is earlier.
1.411 + wait_on_cms_lock_for_scavenge(CMSWaitDuration);
1.412 + } else {
1.413 + // Wait until any cms_lock event or check interval not to call shouldConcurrentCollect permanently
1.414 + wait_on_cms_lock(CMSCheckInterval);
1.415 + }
1.416 + }
1.417 + // Check if we should start a CMS collection cycle
1.418 + if (_collector->shouldConcurrentCollect()) {
1.419 + return;
1.420 + }
1.421 + // .. collection criterion not yet met, let's go back
1.422 + // and wait some more
1.423 + }
1.424 +}
1.425 +
1.426 +// Incremental CMS
1.427 +void ConcurrentMarkSweepThread::start_icms() {
1.428 + assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
1.429 + MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
1.430 + trace_state("start_icms");
1.431 + _should_run = true;
1.432 + iCMS_lock->notify_all();
1.433 +}
1.434 +
1.435 +void ConcurrentMarkSweepThread::stop_icms() {
1.436 + assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
1.437 + MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
1.438 + if (!_should_stop) {
1.439 + trace_state("stop_icms");
1.440 + _should_stop = true;
1.441 + _should_run = false;
1.442 + asynchronous_yield_request();
1.443 + iCMS_lock->notify_all();
1.444 + }
1.445 +}
1.446 +
1.447 +void ConcurrentMarkSweepThread::icms_wait() {
1.448 + assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
1.449 + if (_should_stop && icms_is_enabled()) {
1.450 + MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
1.451 + trace_state("pause_icms");
1.452 + _collector->stats().stop_cms_timer();
1.453 + while(!_should_run && icms_is_enabled()) {
1.454 + iCMS_lock->wait(Mutex::_no_safepoint_check_flag);
1.455 + }
1.456 + _collector->stats().start_cms_timer();
1.457 + _should_stop = false;
1.458 + trace_state("pause_icms end");
1.459 + }
1.460 +}
1.461 +
1.462 +// Note: this method, although exported by the ConcurrentMarkSweepThread,
1.463 +// which is a non-JavaThread, can only be called by a JavaThread.
1.464 +// Currently this is done at vm creation time (post-vm-init) by the
1.465 +// main/Primordial (Java)Thread.
1.466 +// XXX Consider changing this in the future to allow the CMS thread
1.467 +// itself to create this thread?
1.468 +void ConcurrentMarkSweepThread::makeSurrogateLockerThread(TRAPS) {
1.469 + assert(UseConcMarkSweepGC, "SLT thread needed only for CMS GC");
1.470 + assert(_slt == NULL, "SLT already created");
1.471 + _slt = SurrogateLockerThread::make(THREAD);
1.472 +}
