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src/share/vm/memory/threadLocalAllocBuffer.cpp

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  36 // Thread-Local Edens support
  37 
  38 // static member initialization
  39 size_t           ThreadLocalAllocBuffer::_max_size       = 0;
  40 unsigned         ThreadLocalAllocBuffer::_target_refills = 0;
  41 GlobalTLABStats* ThreadLocalAllocBuffer::_global_stats   = NULL;
  42 
  43 void ThreadLocalAllocBuffer::clear_before_allocation() {
  44   _slow_refill_waste += (unsigned)remaining();
  45   make_parsable(true);   // also retire the TLAB
  46 }
  47 
  48 void ThreadLocalAllocBuffer::accumulate_statistics_before_gc() {
  49   global_stats()->initialize();
  50 
  51   for (JavaThread *thread = Threads::first(); thread != NULL; thread = thread->next()) {
  52     thread->tlab().accumulate_statistics();
  53     thread->tlab().initialize_statistics();
  54   }
  55 


  56   // Publish new stats if some allocation occurred.
  57   if (global_stats()->allocation() != 0) {
  58     global_stats()->publish();
  59     if (PrintTLAB) {
  60       global_stats()->print();
  61     }
  62   }
  63 }
  64 
  65 void ThreadLocalAllocBuffer::accumulate_statistics() {
  66   Thread* thread = myThread();
  67   size_t capacity = Universe::heap()->tlab_capacity(thread);
  68   size_t used     = Universe::heap()->tlab_used(thread);
  69 
  70   _gc_waste += (unsigned)remaining();
  71   size_t total_allocated = thread->allocated_bytes();
  72   size_t allocated_since_last_gc = total_allocated - _allocated_before_last_gc;
  73   _allocated_before_last_gc = total_allocated;
  74 
  75   if (PrintTLAB && (_number_of_refills > 0 || Verbose)) {
  76     print_stats("gc");
  77   }
  78 
  79   if (_number_of_refills > 0) {
  80     // Update allocation history if a reasonable amount of eden was allocated.
  81     bool update_allocation_history = used > 0.5 * capacity;
  82 
  83     if (update_allocation_history) {
  84       // Average the fraction of eden allocated in a tlab by this
  85       // thread for use in the next resize operation.
  86       // _gc_waste is not subtracted because it's included in
  87       // "used".
  88       // The result can be larger than 1.0 due to direct to old allocations.
  89       // These allocations should ideally not be counted but since it is not possible
  90       // to filter them out here we just cap the fraction to be at most 1.0.
  91       // Keep alloc_frac as float and not double to avoid the double to float conversion


  99     global_stats()->update_slow_refill_waste(_slow_refill_waste);
 100     global_stats()->update_fast_refill_waste(_fast_refill_waste);
 101 
 102   } else {
 103     assert(_number_of_refills == 0 && _fast_refill_waste == 0 &&
 104            _slow_refill_waste == 0 && _gc_waste          == 0,
 105            "tlab stats == 0");
 106   }
 107   global_stats()->update_slow_allocations(_slow_allocations);
 108 }
 109 
 110 // Fills the current tlab with a dummy filler array to create
 111 // an illusion of a contiguous Eden and optionally retires the tlab.
 112 // Waste accounting should be done in caller as appropriate; see,
 113 // for example, clear_before_allocation().
 114 void ThreadLocalAllocBuffer::make_parsable(bool retire) {
 115   if (end() != NULL) {
 116     invariants();
 117 
 118     if (retire) {
 119       myThread()->incr_allocated_bytes(used_bytes());




 120     }
 121 
 122     CollectedHeap::fill_with_object(top(), hard_end(), retire);
 123 
 124     if (retire || ZeroTLAB) {  // "Reset" the TLAB
 125       set_start(NULL);
 126       set_top(NULL);
 127       set_pf_top(NULL);
 128       set_end(NULL);
 129     }
 130   }
 131   assert(!(retire || ZeroTLAB)  ||
 132          (start() == NULL && end() == NULL && top() == NULL),
 133          "TLAB must be reset");
 134 }
 135 
 136 void ThreadLocalAllocBuffer::resize_all_tlabs() {
 137   if (ResizeTLAB) {
 138     for (JavaThread *thread = Threads::first(); thread != NULL; thread = thread->next()) {
 139       thread->tlab().resize();


 177   if (PrintTLAB && Verbose) {
 178     print_stats("fill");
 179   }
 180   assert(top <= start + new_size - alignment_reserve(), "size too small");
 181   initialize(start, top, start + new_size - alignment_reserve());
 182 
 183   // Reset amount of internal fragmentation
 184   set_refill_waste_limit(initial_refill_waste_limit());
 185 }
 186 
 187 void ThreadLocalAllocBuffer::initialize(HeapWord* start,
 188                                         HeapWord* top,
 189                                         HeapWord* end) {
 190   set_start(start);
 191   set_top(top);
 192   set_pf_top(top);
 193   set_end(end);
 194   invariants();
 195 }
 196 
 197 void ThreadLocalAllocBuffer::initialize() {


 198   initialize(NULL,                    // start
 199              NULL,                    // top
 200              NULL);                   // end
 201 
 202   set_desired_size(initial_desired_size());
 203 
 204   // Following check is needed because at startup the main
 205   // thread is initialized before the heap is.  The initialization for
 206   // this thread is redone in startup_initialization below.
 207   if (Universe::heap() != NULL) {
 208     size_t capacity   = Universe::heap()->tlab_capacity(myThread()) / HeapWordSize;
 209     // Keep alloc_frac as float and not double to avoid the double to float conversion
 210     float alloc_frac = desired_size() * target_refills() / (float) capacity;
 211     _allocation_fraction.sample(alloc_frac);
 212   }
 213 
 214   set_refill_waste_limit(initial_refill_waste_limit());
 215 
 216   initialize_statistics();
 217 }
 218 
 219 void ThreadLocalAllocBuffer::startup_initialization() {
 220 
 221   // Assuming each thread's active tlab is, on average,
 222   // 1/2 full at a GC
 223   _target_refills = 100 / (2 * TLABWasteTargetPercent);
 224   _target_refills = MAX2(_target_refills, (unsigned)1U);
 225 
 226   _global_stats = new GlobalTLABStats();
 227 
 228   // During jvm startup, the main thread is initialized
 229   // before the heap is initialized.  So reinitialize it now.
 230   guarantee(Thread::current()->is_Java_thread(), "tlab initialization thread not Java thread");
 231   Thread::current()->tlab().initialize();



 232 
 233   if (PrintTLAB && Verbose) {
 234     gclog_or_tty->print("TLAB min: " SIZE_FORMAT " initial: " SIZE_FORMAT " max: " SIZE_FORMAT "\n",
 235                         min_size(), Thread::current()->tlab().initial_desired_size(), max_size());
 236   }
 237 }
 238 
 239 size_t ThreadLocalAllocBuffer::initial_desired_size() {
 240   size_t init_sz = 0;
 241 
 242   if (TLABSize > 0) {
 243     init_sz = TLABSize / HeapWordSize;
 244   } else if (global_stats() != NULL) {
 245     // Initial size is a function of the average number of allocating threads.
 246     unsigned nof_threads = global_stats()->allocating_threads_avg();
 247 
 248     init_sz  = (Universe::heap()->tlab_capacity(myThread()) / HeapWordSize) /
 249                       (nof_threads * target_refills());
 250     init_sz = align_object_size(init_sz);
 251   }
 252   init_sz = MIN2(MAX2(init_sz, min_size()), max_size());
 253   return init_sz;
 254 }
 255 
 256 void ThreadLocalAllocBuffer::print_stats(const char* tag) {
 257   Thread* thrd = myThread();
 258   size_t waste = _gc_waste + _slow_refill_waste + _fast_refill_waste;
 259   size_t alloc = _number_of_refills * _desired_size;
 260   double waste_percent = alloc == 0 ? 0.0 :
 261                       100.0 * waste / alloc;
 262   size_t tlab_used  = Universe::heap()->tlab_used(thrd);
 263   gclog_or_tty->print("TLAB: %s thread: " INTPTR_FORMAT " [id: %2d]"
 264                       " desired_size: " SIZE_FORMAT "KB"
 265                       " slow allocs: %d  refill waste: " SIZE_FORMAT "B"
 266                       " alloc:%8.5f %8.0fKB refills: %d waste %4.1f%% gc: %dB"
 267                       " slow: %dB fast: %dB\n",
 268                       tag, thrd, thrd->osthread()->thread_id(),
 269                       _desired_size / (K / HeapWordSize),
 270                       _slow_allocations, _refill_waste_limit * HeapWordSize,
 271                       _allocation_fraction.average(),
 272                       _allocation_fraction.average() * tlab_used / K,
 273                       _number_of_refills, waste_percent,
 274                       _gc_waste * HeapWordSize,
 275                       _slow_refill_waste * HeapWordSize,
 276                       _fast_refill_waste * HeapWordSize);
 277 }
 278 
 279 void ThreadLocalAllocBuffer::verify() {
 280   HeapWord* p = start();
 281   HeapWord* t = top();
 282   HeapWord* prev_p = NULL;
 283   while (p < t) {
 284     oop(p)->verify();
 285     prev_p = p;
 286     p += oop(p)->size();
 287   }
 288   guarantee(p == top(), "end of last object must match end of space");
 289 }
 290 
 291 Thread* ThreadLocalAllocBuffer::myThread() {
 292   return (Thread*)(((char *)this) +
 293                    in_bytes(start_offset()) -
 294                    in_bytes(Thread::tlab_start_offset()));













 295 }
 296 
 297 
 298 GlobalTLABStats::GlobalTLABStats() :
 299   _allocating_threads_avg(TLABAllocationWeight) {
 300 
 301   initialize();
 302 
 303   _allocating_threads_avg.sample(1); // One allocating thread at startup
 304 
 305   if (UsePerfData) {
 306 
 307     EXCEPTION_MARK;
 308     ResourceMark rm;
 309 
 310     char* cname = PerfDataManager::counter_name("tlab", "allocThreads");
 311     _perf_allocating_threads =
 312       PerfDataManager::create_variable(SUN_GC, cname, PerfData::U_None, CHECK);
 313 
 314     cname = PerfDataManager::counter_name("tlab", "fills");




  36 // Thread-Local Edens support
  37 
  38 // static member initialization
  39 size_t           ThreadLocalAllocBuffer::_max_size       = 0;
  40 unsigned         ThreadLocalAllocBuffer::_target_refills = 0;
  41 GlobalTLABStats* ThreadLocalAllocBuffer::_global_stats   = NULL;
  42 
  43 void ThreadLocalAllocBuffer::clear_before_allocation() {
  44   _slow_refill_waste += (unsigned)remaining();
  45   make_parsable(true);   // also retire the TLAB
  46 }
  47 
  48 void ThreadLocalAllocBuffer::accumulate_statistics_before_gc() {
  49   global_stats()->initialize();
  50 
  51   for (JavaThread *thread = Threads::first(); thread != NULL; thread = thread->next()) {
  52     thread->tlab().accumulate_statistics();
  53     thread->tlab().initialize_statistics();
  54   }
  55 
  56   Universe::heap()->accumulate_statistics_all_gclabs();
  57 
  58   // Publish new stats if some allocation occurred.
  59   if (global_stats()->allocation() != 0) {
  60     global_stats()->publish();
  61     if (PrintTLAB) {
  62       global_stats()->print();
  63     }
  64   }
  65 }
  66 
  67 void ThreadLocalAllocBuffer::accumulate_statistics() {
  68   Thread* thread = myThread();
  69   size_t capacity = Universe::heap()->tlab_capacity(thread);
  70   size_t used     = Universe::heap()->tlab_used(thread);
  71 
  72   _gc_waste += (unsigned)remaining();
  73   size_t total_allocated = _gclab ? thread->allocated_bytes_gclab() : thread->allocated_bytes();
  74   size_t allocated_since_last_gc = total_allocated - _allocated_before_last_gc;
  75   _allocated_before_last_gc = total_allocated;
  76 
  77   if (PrintTLAB && (_number_of_refills > 0 || Verbose)) {
  78     print_stats("gc");
  79   }
  80 
  81   if (_number_of_refills > 0) {
  82     // Update allocation history if a reasonable amount of eden was allocated.
  83     bool update_allocation_history = used > 0.5 * capacity;
  84 
  85     if (update_allocation_history) {
  86       // Average the fraction of eden allocated in a tlab by this
  87       // thread for use in the next resize operation.
  88       // _gc_waste is not subtracted because it's included in
  89       // "used".
  90       // The result can be larger than 1.0 due to direct to old allocations.
  91       // These allocations should ideally not be counted but since it is not possible
  92       // to filter them out here we just cap the fraction to be at most 1.0.
  93       // Keep alloc_frac as float and not double to avoid the double to float conversion


 101     global_stats()->update_slow_refill_waste(_slow_refill_waste);
 102     global_stats()->update_fast_refill_waste(_fast_refill_waste);
 103 
 104   } else {
 105     assert(_number_of_refills == 0 && _fast_refill_waste == 0 &&
 106            _slow_refill_waste == 0 && _gc_waste          == 0,
 107            "tlab stats == 0");
 108   }
 109   global_stats()->update_slow_allocations(_slow_allocations);
 110 }
 111 
 112 // Fills the current tlab with a dummy filler array to create
 113 // an illusion of a contiguous Eden and optionally retires the tlab.
 114 // Waste accounting should be done in caller as appropriate; see,
 115 // for example, clear_before_allocation().
 116 void ThreadLocalAllocBuffer::make_parsable(bool retire) {
 117   if (end() != NULL) {
 118     invariants();
 119 
 120     if (retire) {
 121       if (_gclab) {
 122         myThread()->incr_allocated_bytes_gclab(used_bytes());
 123       } else {
 124         myThread()->incr_allocated_bytes(used_bytes());
 125       }
 126     }
 127 
 128     CollectedHeap::fill_with_object(top(), hard_end(), retire);
 129 
 130     if (retire || ZeroTLAB) {  // "Reset" the TLAB
 131       set_start(NULL);
 132       set_top(NULL);
 133       set_pf_top(NULL);
 134       set_end(NULL);
 135     }
 136   }
 137   assert(!(retire || ZeroTLAB)  ||
 138          (start() == NULL && end() == NULL && top() == NULL),
 139          "TLAB must be reset");
 140 }
 141 
 142 void ThreadLocalAllocBuffer::resize_all_tlabs() {
 143   if (ResizeTLAB) {
 144     for (JavaThread *thread = Threads::first(); thread != NULL; thread = thread->next()) {
 145       thread->tlab().resize();


 183   if (PrintTLAB && Verbose) {
 184     print_stats("fill");
 185   }
 186   assert(top <= start + new_size - alignment_reserve(), "size too small");
 187   initialize(start, top, start + new_size - alignment_reserve());
 188 
 189   // Reset amount of internal fragmentation
 190   set_refill_waste_limit(initial_refill_waste_limit());
 191 }
 192 
 193 void ThreadLocalAllocBuffer::initialize(HeapWord* start,
 194                                         HeapWord* top,
 195                                         HeapWord* end) {
 196   set_start(start);
 197   set_top(top);
 198   set_pf_top(top);
 199   set_end(end);
 200   invariants();
 201 }
 202 
 203 void ThreadLocalAllocBuffer::initialize(bool gclab) {
 204   _initialized = true;
 205   _gclab = gclab;
 206   initialize(NULL,                    // start
 207              NULL,                    // top
 208              NULL);                   // end
 209 
 210   set_desired_size(initial_desired_size());
 211 
 212   // Following check is needed because at startup the main
 213   // thread is initialized before the heap is.  The initialization for
 214   // this thread is redone in startup_initialization below.
 215   if (Universe::heap() != NULL) {
 216     size_t capacity   = Universe::heap()->tlab_capacity(myThread()) / HeapWordSize;
 217     // Keep alloc_frac as float and not double to avoid the double to float conversion
 218     float alloc_frac = desired_size() * target_refills() / (float) capacity;
 219     _allocation_fraction.sample(alloc_frac);
 220   }
 221 
 222   set_refill_waste_limit(initial_refill_waste_limit());
 223 
 224   initialize_statistics();
 225 }
 226 
 227 void ThreadLocalAllocBuffer::startup_initialization() {
 228 
 229   // Assuming each thread's active tlab is, on average,
 230   // 1/2 full at a GC
 231   _target_refills = 100 / (2 * TLABWasteTargetPercent);
 232   _target_refills = MAX2(_target_refills, (unsigned)1U);
 233 
 234   _global_stats = new GlobalTLABStats();
 235 
 236   // During jvm startup, the main thread is initialized
 237   // before the heap is initialized.  So reinitialize it now.
 238   guarantee(Thread::current()->is_Java_thread(), "tlab initialization thread not Java thread");
 239   Thread::current()->tlab().initialize(false);
 240   if (UseShenandoahGC) {
 241     Thread::current()->gclab().initialize(true);
 242   }
 243 
 244   if (PrintTLAB && Verbose) {
 245     gclog_or_tty->print("TLAB min: " SIZE_FORMAT " initial: " SIZE_FORMAT " max: " SIZE_FORMAT "\n",
 246                         min_size(), Thread::current()->tlab().initial_desired_size(), max_size());
 247   }
 248 }
 249 
 250 size_t ThreadLocalAllocBuffer::initial_desired_size() {
 251   size_t init_sz = 0;
 252 
 253   if (TLABSize > 0) {
 254     init_sz = TLABSize / HeapWordSize;
 255   } else if (global_stats() != NULL) {
 256     // Initial size is a function of the average number of allocating threads.
 257     unsigned nof_threads = global_stats()->allocating_threads_avg();
 258 
 259     init_sz  = (Universe::heap()->tlab_capacity(myThread()) / HeapWordSize) /
 260                       (nof_threads * target_refills());
 261     init_sz = align_object_size(init_sz);
 262   }
 263   init_sz = MIN2(MAX2(init_sz, min_size()), max_size());
 264   return init_sz;
 265 }
 266 
 267 void ThreadLocalAllocBuffer::print_stats(const char* tag) {
 268   Thread* thrd = myThread();
 269   size_t waste = _gc_waste + _slow_refill_waste + _fast_refill_waste;
 270   size_t alloc = _number_of_refills * _desired_size;
 271   double waste_percent = alloc == 0 ? 0.0 :
 272                       100.0 * waste / alloc;
 273   size_t tlab_used  = Universe::heap()->tlab_used(thrd);
 274   gclog_or_tty->print("TLAB: %s %s thread: " INTPTR_FORMAT " [id: %2d]"
 275                       " desired_size: " SIZE_FORMAT "KB"
 276                       " slow allocs: %d  refill waste: " SIZE_FORMAT "B"
 277                       " alloc:%8.5f %8.0fKB refills: %d waste %4.1f%% gc: %dB"
 278                       " slow: %dB fast: %dB\n",
 279                       tag, _gclab ? "gclab" : "tlab ", p2i(thrd), thrd->osthread()->thread_id(),
 280                       _desired_size / (K / HeapWordSize),
 281                       _slow_allocations, _refill_waste_limit * HeapWordSize,
 282                       _allocation_fraction.average(),
 283                       _allocation_fraction.average() * tlab_used / K,
 284                       _number_of_refills, waste_percent,
 285                       _gc_waste * HeapWordSize,
 286                       _slow_refill_waste * HeapWordSize,
 287                       _fast_refill_waste * HeapWordSize);
 288 }
 289 
 290 void ThreadLocalAllocBuffer::verify() {
 291   HeapWord* p = start();
 292   HeapWord* t = top();
 293   HeapWord* prev_p = NULL;
 294   while (p < t) {
 295     oop(p)->verify();
 296     prev_p = p;
 297     p += oop(p)->size();
 298   }
 299   guarantee(p == top(), "end of last object must match end of space");
 300 }
 301 
 302 Thread* ThreadLocalAllocBuffer::myThread() {
 303   ByteSize gclab_offset = Thread::gclab_start_offset();
 304   ByteSize tlab_offset = Thread::tlab_start_offset();
 305   ByteSize offs = _gclab ? gclab_offset : tlab_offset;
 306   Thread* thread = (Thread*)(((char *)this) +
 307                    in_bytes(start_offset()) - in_bytes(offs));
 308 #ifdef ASSERT
 309   assert(this == (_gclab ? &thread->gclab() : &thread->tlab()), "must be");
 310 #endif
 311   return thread;
 312 }
 313 
 314 void ThreadLocalAllocBuffer::rollback(size_t size) {
 315   HeapWord* old_top = top();
 316   if (old_top != NULL) { // Pathological case: we accept that we can't rollback.
 317     set_top(old_top - size);
 318   }
 319 }
 320 
 321 
 322 GlobalTLABStats::GlobalTLABStats() :
 323   _allocating_threads_avg(TLABAllocationWeight) {
 324 
 325   initialize();
 326 
 327   _allocating_threads_avg.sample(1); // One allocating thread at startup
 328 
 329   if (UsePerfData) {
 330 
 331     EXCEPTION_MARK;
 332     ResourceMark rm;
 333 
 334     char* cname = PerfDataManager::counter_name("tlab", "allocThreads");
 335     _perf_allocating_threads =
 336       PerfDataManager::create_variable(SUN_GC, cname, PerfData::U_None, CHECK);
 337 
 338     cname = PerfDataManager::counter_name("tlab", "fills");


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