1 /*
   2  * Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/stringTable.hpp"
  27 #include "classfile/systemDictionary.hpp"
  28 #include "code/codeCache.hpp"
  29 #include "gc_interface/collectedHeap.inline.hpp"
  30 #include "memory/sharedHeap.hpp"
  31 #include "oops/oop.inline.hpp"
  32 #include "runtime/atomic.inline.hpp"
  33 #include "runtime/fprofiler.hpp"
  34 #include "runtime/java.hpp"
  35 #include "services/management.hpp"
  36 #include "utilities/copy.hpp"
  37 #include "utilities/workgroup.hpp"
  38 
  39 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  40 
  41 SharedHeap* SharedHeap::_sh;
  42 
  43 // The set of potentially parallel tasks in root scanning.
  44 enum SH_process_roots_tasks {
  45   SH_PS_Universe_oops_do,
  46   SH_PS_JNIHandles_oops_do,
  47   SH_PS_ObjectSynchronizer_oops_do,
  48   SH_PS_FlatProfiler_oops_do,
  49   SH_PS_Management_oops_do,
  50   SH_PS_SystemDictionary_oops_do,
  51   SH_PS_ClassLoaderDataGraph_oops_do,
  52   SH_PS_jvmti_oops_do,
  53   SH_PS_CodeCache_oops_do,
  54   // Leave this one last.
  55   SH_PS_NumElements
  56 };
  57 
  58 SharedHeap::SharedHeap(CollectorPolicy* policy_) :
  59   CollectedHeap(),
  60   _collector_policy(policy_),
  61   _rem_set(NULL),
  62   _strong_roots_scope(NULL),
  63   _strong_roots_parity(0),
  64   _process_strong_tasks(new SubTasksDone(SH_PS_NumElements)),
  65   _workers(NULL)
  66 {
  67   if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
  68     vm_exit_during_initialization("Failed necessary allocation.");
  69   }
  70   _sh = this;  // ch is static, should be set only once.
  71   if ((UseParNewGC ||
  72       (UseConcMarkSweepGC && (CMSParallelInitialMarkEnabled ||
  73                               CMSParallelRemarkEnabled)) ||
  74        UseG1GC) &&
  75       ParallelGCThreads > 0) {
  76     _workers = new FlexibleWorkGang("Parallel GC Threads", ParallelGCThreads,
  77                             /* are_GC_task_threads */true,
  78                             /* are_ConcurrentGC_threads */false);
  79     if (_workers == NULL) {
  80       vm_exit_during_initialization("Failed necessary allocation.");
  81     } else {
  82       _workers->initialize_workers();
  83     }
  84   }
  85 }
  86 
  87 int SharedHeap::n_termination() {
  88   return _process_strong_tasks->n_threads();
  89 }
  90 
  91 void SharedHeap::set_n_termination(int t) {
  92   _process_strong_tasks->set_n_threads(t);
  93 }
  94 
  95 bool SharedHeap::heap_lock_held_for_gc() {
  96   Thread* t = Thread::current();
  97   return    Heap_lock->owned_by_self()
  98          || (   (t->is_GC_task_thread() ||  t->is_VM_thread())
  99              && _thread_holds_heap_lock_for_gc);
 100 }
 101 
 102 void SharedHeap::set_par_threads(uint t) {
 103   assert(t == 0 || !UseSerialGC, "Cannot have parallel threads");
 104   _n_par_threads = t;
 105   _process_strong_tasks->set_n_threads(t);
 106 }
 107 
 108 #ifdef ASSERT
 109 class AssertNonScavengableClosure: public OopClosure {
 110 public:
 111   virtual void do_oop(oop* p) {
 112     assert(!Universe::heap()->is_in_partial_collection(*p),
 113       "Referent should not be scavengable.");  }
 114   virtual void do_oop(narrowOop* p) { ShouldNotReachHere(); }
 115 };
 116 static AssertNonScavengableClosure assert_is_non_scavengable_closure;
 117 #endif
 118 
 119 SharedHeap::StrongRootsScope* SharedHeap::active_strong_roots_scope() const {
 120   return _strong_roots_scope;
 121 }
 122 void SharedHeap::register_strong_roots_scope(SharedHeap::StrongRootsScope* scope) {
 123   assert(_strong_roots_scope == NULL, "Should only have one StrongRootsScope active");
 124   assert(scope != NULL, "Illegal argument");
 125   _strong_roots_scope = scope;
 126 }
 127 void SharedHeap::unregister_strong_roots_scope(SharedHeap::StrongRootsScope* scope) {
 128   assert(_strong_roots_scope == scope, "Wrong scope unregistered");
 129   _strong_roots_scope = NULL;
 130 }
 131 
 132 void SharedHeap::change_strong_roots_parity() {
 133   // Also set the new collection parity.
 134   assert(_strong_roots_parity >= 0 && _strong_roots_parity <= 2,
 135          "Not in range.");
 136   _strong_roots_parity++;
 137   if (_strong_roots_parity == 3) _strong_roots_parity = 1;
 138   assert(_strong_roots_parity >= 1 && _strong_roots_parity <= 2,
 139          "Not in range.");
 140 }
 141 
 142 SharedHeap::StrongRootsScope::StrongRootsScope(SharedHeap* heap, bool activate)
 143   : MarkScope(activate), _sh(heap), _n_workers_done_with_threads(0)
 144 {
 145   if (_active) {
 146     _sh->register_strong_roots_scope(this);
 147     _sh->change_strong_roots_parity();
 148     // Zero the claimed high water mark in the StringTable
 149     StringTable::clear_parallel_claimed_index();
 150   }
 151 }
 152 
 153 SharedHeap::StrongRootsScope::~StrongRootsScope() {
 154   if (_active) {
 155     _sh->unregister_strong_roots_scope(this);
 156   }
 157 }
 158 
 159 Monitor* SharedHeap::StrongRootsScope::_lock = new Monitor(Mutex::leaf, "StrongRootsScope lock", false);
 160 
 161 void SharedHeap::StrongRootsScope::mark_worker_done_with_threads(uint n_workers) {
 162 #if INCLUDE_ALL_GCS
 163   // The Thread work barrier is only needed by G1 Class Unloading.
 164   // No need to use the barrier if this is single-threaded code.
 165   if (UseG1GC && G1ClassUnloadingEnabled && n_workers > 0) {
 166     uint new_value = (uint)Atomic::add(1, &_n_workers_done_with_threads);
 167     if (new_value == n_workers) {
 168       // This thread is last. Notify the others.
 169       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
 170       _lock->notify_all();
 171     }
 172   }
 173 #endif
 174 }
 175 
 176 void SharedHeap::StrongRootsScope::wait_until_all_workers_done_with_threads(uint n_workers) {
 177 #if INCLUDE_ALL_GCS
 178   assert(UseG1GC,                 "Currently only used by G1");
 179   assert(G1ClassUnloadingEnabled, "Currently only needed when doing G1 Class Unloading");
 180 
 181   // No need to use the barrier if this is single-threaded code.
 182   if (n_workers > 0 && (uint)_n_workers_done_with_threads != n_workers) {
 183     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
 184     while ((uint)_n_workers_done_with_threads != n_workers) {
 185       _lock->wait(Mutex::_no_safepoint_check_flag, 0, false);
 186     }
 187   }
 188 #endif
 189 }
 190 
 191 void SharedHeap::process_roots(bool activate_scope,
 192                                ScanningOption so,
 193                                OopClosure* strong_roots,
 194                                OopClosure* weak_roots,
 195                                CLDClosure* strong_cld_closure,
 196                                CLDClosure* weak_cld_closure,
 197                                CodeBlobClosure* code_roots) {
 198   StrongRootsScope srs(this, activate_scope);
 199 
 200   // General roots.
 201   assert(_strong_roots_parity != 0, "must have called prologue code");
 202   assert(code_roots != NULL, "code root closure should always be set");
 203   // _n_termination for _process_strong_tasks should be set up stream
 204   // in a method not running in a GC worker.  Otherwise the GC worker
 205   // could be trying to change the termination condition while the task
 206   // is executing in another GC worker.
 207 
 208   // Iterating over the CLDG and the Threads are done early to allow G1 to
 209   // first process the strong CLDs and nmethods and then, after a barrier,
 210   // let the thread process the weak CLDs and nmethods.
 211 
 212   if (!_process_strong_tasks->is_task_claimed(SH_PS_ClassLoaderDataGraph_oops_do)) {
 213     ClassLoaderDataGraph::roots_cld_do(strong_cld_closure, weak_cld_closure);
 214   }
 215 
 216   // Some CLDs contained in the thread frames should be considered strong.
 217   // Don't process them if they will be processed during the ClassLoaderDataGraph phase.
 218   CLDClosure* roots_from_clds_p = (strong_cld_closure != weak_cld_closure) ? strong_cld_closure : NULL;
 219   // Only process code roots from thread stacks if we aren't visiting the entire CodeCache anyway
 220   CodeBlobClosure* roots_from_code_p = (so & SO_AllCodeCache) ? NULL : code_roots;
 221 
 222   Threads::possibly_parallel_oops_do(strong_roots, roots_from_clds_p, roots_from_code_p);
 223 
 224   // This is the point where this worker thread will not find more strong CLDs/nmethods.
 225   // Report this so G1 can synchronize the strong and weak CLDs/nmethods processing.
 226   active_strong_roots_scope()->mark_worker_done_with_threads(n_par_threads());
 227 
 228   if (!_process_strong_tasks->is_task_claimed(SH_PS_Universe_oops_do)) {
 229     Universe::oops_do(strong_roots);
 230   }
 231   // Global (strong) JNI handles
 232   if (!_process_strong_tasks->is_task_claimed(SH_PS_JNIHandles_oops_do))
 233     JNIHandles::oops_do(strong_roots);
 234 
 235   if (!_process_strong_tasks-> is_task_claimed(SH_PS_ObjectSynchronizer_oops_do))
 236     ObjectSynchronizer::oops_do(strong_roots);
 237   if (!_process_strong_tasks->is_task_claimed(SH_PS_FlatProfiler_oops_do))
 238     FlatProfiler::oops_do(strong_roots);
 239   if (!_process_strong_tasks->is_task_claimed(SH_PS_Management_oops_do))
 240     Management::oops_do(strong_roots);
 241   if (!_process_strong_tasks->is_task_claimed(SH_PS_jvmti_oops_do))
 242     JvmtiExport::oops_do(strong_roots);
 243 
 244   if (!_process_strong_tasks->is_task_claimed(SH_PS_SystemDictionary_oops_do)) {
 245     SystemDictionary::roots_oops_do(strong_roots, weak_roots);
 246   }
 247 
 248   // All threads execute the following. A specific chunk of buckets
 249   // from the StringTable are the individual tasks.
 250   if (weak_roots != NULL) {
 251     if (CollectedHeap::use_parallel_gc_threads()) {
 252       StringTable::possibly_parallel_oops_do(weak_roots);
 253     } else {
 254       StringTable::oops_do(weak_roots);
 255     }
 256   }
 257 
 258   if (!_process_strong_tasks->is_task_claimed(SH_PS_CodeCache_oops_do)) {
 259     if (so & SO_ScavengeCodeCache) {
 260       assert(code_roots != NULL, "must supply closure for code cache");
 261 
 262       // We only visit parts of the CodeCache when scavenging.
 263       CodeCache::scavenge_root_nmethods_do(code_roots);
 264     }
 265     if (so & SO_AllCodeCache) {
 266       assert(code_roots != NULL, "must supply closure for code cache");
 267 
 268       // CMSCollector uses this to do intermediate-strength collections.
 269       // We scan the entire code cache, since CodeCache::do_unloading is not called.
 270       CodeCache::blobs_do(code_roots);
 271     }
 272     // Verify that the code cache contents are not subject to
 273     // movement by a scavenging collection.
 274     DEBUG_ONLY(CodeBlobToOopClosure assert_code_is_non_scavengable(&assert_is_non_scavengable_closure, !CodeBlobToOopClosure::FixRelocations));
 275     DEBUG_ONLY(CodeCache::asserted_non_scavengable_nmethods_do(&assert_code_is_non_scavengable));
 276   }
 277 
 278   _process_strong_tasks->all_tasks_completed();
 279 }
 280 
 281 void SharedHeap::process_all_roots(bool activate_scope,
 282                                    ScanningOption so,
 283                                    OopClosure* roots,
 284                                    CLDClosure* cld_closure,
 285                                    CodeBlobClosure* code_closure) {
 286   process_roots(activate_scope, so,
 287                 roots, roots,
 288                 cld_closure, cld_closure,
 289                 code_closure);
 290 }
 291 
 292 void SharedHeap::process_strong_roots(bool activate_scope,
 293                                       ScanningOption so,
 294                                       OopClosure* roots,
 295                                       CLDClosure* cld_closure,
 296                                       CodeBlobClosure* code_closure) {
 297   process_roots(activate_scope, so,
 298                 roots, NULL,
 299                 cld_closure, NULL,
 300                 code_closure);
 301 }
 302 
 303 
 304 class AlwaysTrueClosure: public BoolObjectClosure {
 305 public:
 306   bool do_object_b(oop p) { return true; }
 307 };
 308 static AlwaysTrueClosure always_true;
 309 
 310 void SharedHeap::process_weak_roots(OopClosure* root_closure) {
 311   // Global (weak) JNI handles
 312   JNIHandles::weak_oops_do(&always_true, root_closure);
 313 }
 314 
 315 void SharedHeap::set_barrier_set(BarrierSet* bs) {
 316   _barrier_set = bs;
 317   // Cached barrier set for fast access in oops
 318   oopDesc::set_bs(bs);
 319 }
 320 
 321 void SharedHeap::post_initialize() {
 322   CollectedHeap::post_initialize();
 323   ref_processing_init();
 324 }
 325 
 326 void SharedHeap::ref_processing_init() {}
 327 
 328 // Some utilities.
 329 void SharedHeap::print_size_transition(outputStream* out,
 330                                        size_t bytes_before,
 331                                        size_t bytes_after,
 332                                        size_t capacity) {
 333   out->print(" " SIZE_FORMAT "%s->" SIZE_FORMAT "%s(" SIZE_FORMAT "%s)",
 334              byte_size_in_proper_unit(bytes_before),
 335              proper_unit_for_byte_size(bytes_before),
 336              byte_size_in_proper_unit(bytes_after),
 337              proper_unit_for_byte_size(bytes_after),
 338              byte_size_in_proper_unit(capacity),
 339              proper_unit_for_byte_size(capacity));
 340 }
--- EOF ---