1 /*
   2  * Copyright (c) 2014, 2015, 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 "gc/g1/g1Allocator.inline.hpp"
  27 #include "gc/g1/g1CollectedHeap.inline.hpp"
  28 #include "gc/g1/g1CollectorPolicy.hpp"
  29 #include "gc/g1/g1MarkSweep.hpp"
  30 #include "gc/g1/heapRegion.inline.hpp"
  31 #include "gc/g1/heapRegionSet.inline.hpp"
  32 
  33 G1DefaultAllocator::G1DefaultAllocator(G1CollectedHeap* heap) :
  34   G1Allocator(heap),
  35   _retained_old_gc_alloc_region(NULL),
  36   _survivor_gc_alloc_region(heap->alloc_buffer_stats(InCSetState::Young)),
  37   _old_gc_alloc_region(heap->alloc_buffer_stats(InCSetState::Old)) {
  38 }
  39 
  40 void G1DefaultAllocator::init_mutator_alloc_region() {
  41   assert(_mutator_alloc_region.get() == NULL, "pre-condition");
  42   _mutator_alloc_region.init();
  43 }
  44 
  45 void G1DefaultAllocator::release_mutator_alloc_region() {
  46   _mutator_alloc_region.release();
  47   assert(_mutator_alloc_region.get() == NULL, "post-condition");
  48 }
  49 
  50 void G1Allocator::reuse_retained_old_region(EvacuationInfo& evacuation_info,
  51                                             OldGCAllocRegion* old,
  52                                             HeapRegion** retained_old) {
  53   HeapRegion* retained_region = *retained_old;
  54   *retained_old = NULL;
  55   assert(retained_region == NULL || !retained_region->is_archive(),
  56          err_msg("Archive region should not be alloc region (index %u)", retained_region->hrm_index()));
  57 
  58   // We will discard the current GC alloc region if:
  59   // a) it's in the collection set (it can happen!),
  60   // b) it's already full (no point in using it),
  61   // c) it's empty (this means that it was emptied during
  62   // a cleanup and it should be on the free list now), or
  63   // d) it's humongous (this means that it was emptied
  64   // during a cleanup and was added to the free list, but
  65   // has been subsequently used to allocate a humongous
  66   // object that may be less than the region size).
  67   if (retained_region != NULL &&
  68       !retained_region->in_collection_set() &&
  69       !(retained_region->top() == retained_region->end()) &&
  70       !retained_region->is_empty() &&
  71       !retained_region->is_humongous()) {
  72     retained_region->record_timestamp();
  73     // The retained region was added to the old region set when it was
  74     // retired. We have to remove it now, since we don't allow regions
  75     // we allocate to in the region sets. We'll re-add it later, when
  76     // it's retired again.
  77     _g1h->old_set_remove(retained_region);
  78     bool during_im = _g1h->collector_state()->during_initial_mark_pause();
  79     retained_region->note_start_of_copying(during_im);
  80     old->set(retained_region);
  81     _g1h->hr_printer()->reuse(retained_region);
  82     evacuation_info.set_alloc_regions_used_before(retained_region->used());
  83   }
  84 }
  85 
  86 void G1DefaultAllocator::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
  87   assert_at_safepoint(true /* should_be_vm_thread */);
  88 
  89   G1Allocator::init_gc_alloc_regions(evacuation_info);
  90 
  91   _survivor_gc_alloc_region.init();
  92   _old_gc_alloc_region.init();
  93   reuse_retained_old_region(evacuation_info,
  94                             &_old_gc_alloc_region,
  95                             &_retained_old_gc_alloc_region);
  96 }
  97 
  98 void G1DefaultAllocator::release_gc_alloc_regions(EvacuationInfo& evacuation_info) {
  99   AllocationContext_t context = AllocationContext::current();
 100   evacuation_info.set_allocation_regions(survivor_gc_alloc_region(context)->count() +
 101                                          old_gc_alloc_region(context)->count());
 102   survivor_gc_alloc_region(context)->release();
 103   // If we have an old GC alloc region to release, we'll save it in
 104   // _retained_old_gc_alloc_region. If we don't
 105   // _retained_old_gc_alloc_region will become NULL. This is what we
 106   // want either way so no reason to check explicitly for either
 107   // condition.
 108   _retained_old_gc_alloc_region = old_gc_alloc_region(context)->release();
 109   if (_retained_old_gc_alloc_region != NULL) {
 110     _retained_old_gc_alloc_region->record_retained_region();
 111   }
 112 
 113   _g1h->alloc_buffer_stats(InCSetState::Young)->adjust_desired_plab_sz();
 114   _g1h->alloc_buffer_stats(InCSetState::Old)->adjust_desired_plab_sz();
 115 }
 116 
 117 void G1DefaultAllocator::abandon_gc_alloc_regions() {
 118   assert(survivor_gc_alloc_region(AllocationContext::current())->get() == NULL, "pre-condition");
 119   assert(old_gc_alloc_region(AllocationContext::current())->get() == NULL, "pre-condition");
 120   _retained_old_gc_alloc_region = NULL;
 121 }
 122 
 123 G1PLAB::G1PLAB(size_t gclab_word_size) :
 124   PLAB(gclab_word_size), _retired(true) { }
 125 
 126 size_t G1Allocator::unsafe_max_tlab_alloc(AllocationContext_t context) {
 127   // Return the remaining space in the cur alloc region, but not less than
 128   // the min TLAB size.
 129 
 130   // Also, this value can be at most the humongous object threshold,
 131   // since we can't allow tlabs to grow big enough to accommodate
 132   // humongous objects.
 133 
 134   HeapRegion* hr = mutator_alloc_region(context)->get();
 135   size_t max_tlab = _g1h->max_tlab_size() * wordSize;
 136   if (hr == NULL) {
 137     return max_tlab;
 138   } else {
 139     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
 140   }
 141 }
 142 
 143 HeapWord* G1Allocator::par_allocate_during_gc(InCSetState dest,
 144                                               size_t word_size,
 145                                               AllocationContext_t context) {
 146   switch (dest.value()) {
 147     case InCSetState::Young:
 148       return survivor_attempt_allocation(word_size, context);
 149     case InCSetState::Old:
 150       return old_attempt_allocation(word_size, context);
 151     default:
 152       ShouldNotReachHere();
 153       return NULL; // Keep some compilers happy
 154   }
 155 }
 156 
 157 bool G1Allocator::survivor_is_full(AllocationContext_t context) const {
 158   return _survivor_is_full;
 159 }
 160 
 161 bool G1Allocator::old_is_full(AllocationContext_t context) const {
 162   return _old_is_full;    
 163 }
 164 
 165 void G1Allocator::set_survivor_full(AllocationContext_t context) {
 166   _survivor_is_full = true;
 167 }
 168 
 169 void G1Allocator::set_old_full(AllocationContext_t context) {
 170   _old_is_full = true;
 171 }
 172 
 173 HeapWord* G1Allocator::survivor_attempt_allocation(size_t word_size,
 174                                                    AllocationContext_t context) {
 175   assert(!_g1h->is_humongous(word_size),
 176          "we should not be seeing humongous-size allocations in this path");
 177 
 178   HeapWord* result = survivor_gc_alloc_region(context)->attempt_allocation(word_size,
 179                                                                            false /* bot_updates */);
 180   if (result == NULL && !survivor_is_full(context)) {
 181     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
 182     result = survivor_gc_alloc_region(context)->attempt_allocation_locked(word_size,
 183                                                                           false /* bot_updates */);
 184     if (result == NULL) {
 185       set_survivor_full(context);
 186     }
 187   }
 188   if (result != NULL) {
 189     _g1h->dirty_young_block(result, word_size);
 190   }
 191   return result;
 192 }
 193 
 194 HeapWord* G1Allocator::old_attempt_allocation(size_t word_size,
 195                                               AllocationContext_t context) {
 196   assert(!_g1h->is_humongous(word_size),
 197          "we should not be seeing humongous-size allocations in this path");
 198 
 199   HeapWord* result = old_gc_alloc_region(context)->attempt_allocation(word_size,
 200                                                                       true /* bot_updates */);
 201   if (result == NULL && !old_is_full(context)) {
 202     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
 203     result = old_gc_alloc_region(context)->attempt_allocation_locked(word_size,
 204                                                                      true /* bot_updates */);
 205     if (result == NULL) {
 206       set_old_full(context);
 207     }
 208   }
 209   return result;
 210 }
 211 
 212 void G1Allocator::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
 213   _survivor_is_full = false;
 214   _old_is_full = false;
 215 }
 216 
 217 G1PLABAllocator::G1PLABAllocator(G1Allocator* allocator) :
 218   _g1h(G1CollectedHeap::heap()),
 219   _allocator(allocator),
 220   _survivor_alignment_bytes(calc_survivor_alignment_bytes()) {
 221   for (size_t i = 0; i < ARRAY_SIZE(_direct_allocated); i++) {
 222     _direct_allocated[i] = 0;
 223   }
 224 }
 225 
 226 bool G1PLABAllocator::may_throw_away_buffer(size_t const allocation_word_sz, size_t const buffer_size) const {
 227   return (allocation_word_sz * 100 < buffer_size * ParallelGCBufferWastePct);
 228 }
 229 
 230 HeapWord* G1PLABAllocator::allocate_direct_or_new_plab(InCSetState dest,
 231                                                        size_t word_sz,
 232                                                        AllocationContext_t context,
 233                                                        bool* plab_refill_failed) {
 234   size_t plab_word_size = G1CollectedHeap::heap()->desired_plab_sz(dest);
 235   size_t required_in_plab = word_sz + PLAB::alignment_reserve();
 236 
 237   // Only get a new PLAB if the allocation fits and it would not waste more than
 238   // ParallelGCBufferWastePct in the existing buffer.
 239   if ((required_in_plab <= plab_word_size) &&
 240     may_throw_away_buffer(required_in_plab, plab_word_size)) {
 241 
 242     G1PLAB* alloc_buf = alloc_buffer(dest, context);
 243     alloc_buf->retire();
 244 
 245     HeapWord* buf = _allocator->par_allocate_during_gc(dest, plab_word_size, context);
 246     if (buf != NULL) {
 247       // Otherwise.
 248       alloc_buf->set_word_size(plab_word_size);
 249       alloc_buf->set_buf(buf);
 250 
 251       HeapWord* const obj = alloc_buf->allocate(word_sz);
 252       assert(obj != NULL, err_msg("PLAB should have been big enough, tried to allocate "
 253                                   SIZE_FORMAT " with alignment reserve " SIZE_FORMAT " PLAB size " SIZE_FORMAT,
 254                                   word_sz, PLAB::alignment_reserve(), plab_word_size));
 255       return obj;
 256     }
 257     // Otherwise.
 258     *plab_refill_failed = true;
 259   }
 260   // Try direct allocation.
 261   HeapWord* result = _allocator->par_allocate_during_gc(dest, word_sz, context);
 262   if (result != NULL) {
 263     _direct_allocated[dest.value()] += word_sz;
 264   }
 265   return result;
 266 }
 267 
 268 void G1PLABAllocator::undo_allocation(InCSetState dest, HeapWord* obj, size_t word_sz, AllocationContext_t context) {
 269   alloc_buffer(dest, context)->undo_allocation(obj, word_sz);
 270 }
 271 
 272 G1DefaultPLABAllocator::G1DefaultPLABAllocator(G1Allocator* allocator) :
 273   G1PLABAllocator(allocator),
 274   _surviving_alloc_buffer(_g1h->desired_plab_sz(InCSetState::Young)),
 275   _tenured_alloc_buffer(_g1h->desired_plab_sz(InCSetState::Old)) {
 276   for (uint state = 0; state < InCSetState::Num; state++) {
 277     _alloc_buffers[state] = NULL;
 278   }
 279   _alloc_buffers[InCSetState::Young] = &_surviving_alloc_buffer;
 280   _alloc_buffers[InCSetState::Old]  = &_tenured_alloc_buffer;
 281 }
 282 
 283 void G1DefaultPLABAllocator::flush_and_retire_stats() {
 284   for (uint state = 0; state < InCSetState::Num; state++) {
 285     G1PLAB* const buf = _alloc_buffers[state];
 286     if (buf != NULL) {
 287       G1EvacStats* stats = _g1h->alloc_buffer_stats(state);
 288       buf->flush_and_retire_stats(stats);
 289       stats->add_direct_allocated(_direct_allocated[state]);
 290       _direct_allocated[state] = 0;
 291     }
 292   }
 293 }
 294 
 295 void G1DefaultPLABAllocator::waste(size_t& wasted, size_t& undo_wasted) {
 296   wasted = 0;
 297   undo_wasted = 0;
 298   for (uint state = 0; state < InCSetState::Num; state++) {
 299     G1PLAB * const buf = _alloc_buffers[state];
 300     if (buf != NULL) {
 301       wasted += buf->waste();
 302       undo_wasted += buf->undo_waste();
 303     }
 304   }
 305 }
 306 
 307 G1ArchiveAllocator* G1ArchiveAllocator::create_allocator(G1CollectedHeap* g1h) {
 308   // Create the archive allocator, and also enable archive object checking
 309   // in mark-sweep, since we will be creating archive regions.
 310   G1ArchiveAllocator* result =  new G1ArchiveAllocator(g1h);
 311   G1MarkSweep::enable_archive_object_check();
 312   return result;
 313 }
 314 
 315 bool G1ArchiveAllocator::alloc_new_region() {
 316   // Allocate the highest free region in the reserved heap,
 317   // and add it to our list of allocated regions. It is marked
 318   // archive and added to the old set.
 319   HeapRegion* hr = _g1h->alloc_highest_free_region();
 320   if (hr == NULL) {
 321     return false;
 322   }
 323   assert(hr->is_empty(), err_msg("expected empty region (index %u)", hr->hrm_index()));
 324   hr->set_archive();
 325   _g1h->old_set_add(hr);
 326   _g1h->hr_printer()->alloc(hr, G1HRPrinter::Archive);
 327   _allocated_regions.append(hr);
 328   _allocation_region = hr;
 329 
 330   // Set up _bottom and _max to begin allocating in the lowest
 331   // min_region_size'd chunk of the allocated G1 region.
 332   _bottom = hr->bottom();
 333   _max = _bottom + HeapRegion::min_region_size_in_words();
 334 
 335   // Tell mark-sweep that objects in this region are not to be marked.
 336   G1MarkSweep::mark_range_archive(MemRegion(_bottom, HeapRegion::GrainWords));
 337 
 338   // Since we've modified the old set, call update_sizes.
 339   _g1h->g1mm()->update_sizes();
 340   return true;
 341 }
 342 
 343 HeapWord* G1ArchiveAllocator::archive_mem_allocate(size_t word_size) {
 344   assert(word_size != 0, "size must not be zero");
 345   if (_allocation_region == NULL) {
 346     if (!alloc_new_region()) {
 347       return NULL;
 348     }
 349   }
 350   HeapWord* old_top = _allocation_region->top();
 351   assert(_bottom >= _allocation_region->bottom(),
 352          err_msg("inconsistent allocation state: " PTR_FORMAT " < " PTR_FORMAT,
 353                  p2i(_bottom), p2i(_allocation_region->bottom())));
 354   assert(_max <= _allocation_region->end(),
 355          err_msg("inconsistent allocation state: " PTR_FORMAT " > " PTR_FORMAT,
 356                  p2i(_max), p2i(_allocation_region->end())));
 357   assert(_bottom <= old_top && old_top <= _max,
 358          err_msg("inconsistent allocation state: expected "
 359                  PTR_FORMAT " <= " PTR_FORMAT " <= " PTR_FORMAT,
 360                  p2i(_bottom), p2i(old_top), p2i(_max)));
 361 
 362   // Allocate the next word_size words in the current allocation chunk.
 363   // If allocation would cross the _max boundary, insert a filler and begin
 364   // at the base of the next min_region_size'd chunk. Also advance to the next
 365   // chunk if we don't yet cross the boundary, but the remainder would be too
 366   // small to fill.
 367   HeapWord* new_top = old_top + word_size;
 368   size_t remainder = pointer_delta(_max, new_top);
 369   if ((new_top > _max) ||
 370       ((new_top < _max) && (remainder < CollectedHeap::min_fill_size()))) {
 371     if (old_top != _max) {
 372       size_t fill_size = pointer_delta(_max, old_top);
 373       CollectedHeap::fill_with_object(old_top, fill_size);
 374       _summary_bytes_used += fill_size * HeapWordSize;
 375     }
 376     _allocation_region->set_top(_max);
 377     old_top = _bottom = _max;
 378 
 379     // Check if we've just used up the last min_region_size'd chunk
 380     // in the current region, and if so, allocate a new one.
 381     if (_bottom != _allocation_region->end()) {
 382       _max = _bottom + HeapRegion::min_region_size_in_words();
 383     } else {
 384       if (!alloc_new_region()) {
 385         return NULL;
 386       }
 387       old_top = _allocation_region->bottom();
 388     }
 389   }
 390   _allocation_region->set_top(old_top + word_size);
 391   _summary_bytes_used += word_size * HeapWordSize;
 392 
 393   return old_top;
 394 }
 395 
 396 void G1ArchiveAllocator::complete_archive(GrowableArray<MemRegion>* ranges,
 397                                           size_t end_alignment_in_bytes) {
 398   assert((end_alignment_in_bytes >> LogHeapWordSize) < HeapRegion::min_region_size_in_words(),
 399           err_msg("alignment " SIZE_FORMAT " too large", end_alignment_in_bytes));
 400   assert(is_size_aligned(end_alignment_in_bytes, HeapWordSize),
 401          err_msg("alignment " SIZE_FORMAT " is not HeapWord (%u) aligned", end_alignment_in_bytes, HeapWordSize));
 402 
 403   // If we've allocated nothing, simply return.
 404   if (_allocation_region == NULL) {
 405     return;
 406   }
 407 
 408   // If an end alignment was requested, insert filler objects.
 409   if (end_alignment_in_bytes != 0) {
 410     HeapWord* currtop = _allocation_region->top();
 411     HeapWord* newtop = (HeapWord*)align_pointer_up(currtop, end_alignment_in_bytes);
 412     size_t fill_size = pointer_delta(newtop, currtop);
 413     if (fill_size != 0) {
 414       if (fill_size < CollectedHeap::min_fill_size()) {
 415         // If the required fill is smaller than we can represent,
 416         // bump up to the next aligned address. We know we won't exceed the current
 417         // region boundary because the max supported alignment is smaller than the min
 418         // region size, and because the allocation code never leaves space smaller than
 419         // the min_fill_size at the top of the current allocation region.
 420         newtop = (HeapWord*)align_pointer_up(currtop + CollectedHeap::min_fill_size(),
 421                                              end_alignment_in_bytes);
 422         fill_size = pointer_delta(newtop, currtop);
 423       }
 424       HeapWord* fill = archive_mem_allocate(fill_size);
 425       CollectedHeap::fill_with_objects(fill, fill_size);
 426     }
 427   }
 428 
 429   // Loop through the allocated regions, and create MemRegions summarizing
 430   // the allocated address range, combining contiguous ranges. Add the
 431   // MemRegions to the GrowableArray provided by the caller.
 432   int index = _allocated_regions.length() - 1;
 433   assert(_allocated_regions.at(index) == _allocation_region,
 434          err_msg("expected region %u at end of array, found %u",
 435                  _allocation_region->hrm_index(), _allocated_regions.at(index)->hrm_index()));
 436   HeapWord* base_address = _allocation_region->bottom();
 437   HeapWord* top = base_address;
 438 
 439   while (index >= 0) {
 440     HeapRegion* next = _allocated_regions.at(index);
 441     HeapWord* new_base = next->bottom();
 442     HeapWord* new_top = next->top();
 443     if (new_base != top) {
 444       ranges->append(MemRegion(base_address, pointer_delta(top, base_address)));
 445       base_address = new_base;
 446     }
 447     top = new_top;
 448     index = index - 1;
 449   }
 450 
 451   assert(top != base_address, err_msg("zero-sized range, address " PTR_FORMAT, p2i(base_address)));
 452   ranges->append(MemRegion(base_address, pointer_delta(top, base_address)));
 453   _allocated_regions.clear();
 454   _allocation_region = NULL;
 455 };