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      1 /*
      2  * Copyright (C) 2014 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #include "bump_pointer_space.h"
     18 #include "bump_pointer_space-inl.h"
     19 #include "mirror/object-inl.h"
     20 #include "mirror/class-inl.h"
     21 #include "thread_list.h"
     22 
     23 namespace art {
     24 namespace gc {
     25 namespace space {
     26 
     27 // If a region has live objects whose size is less than this percent
     28 // value of the region size, evaculate the region.
     29 static constexpr uint kEvaculateLivePercentThreshold = 75U;
     30 
     31 RegionSpace* RegionSpace::Create(const std::string& name, size_t capacity,
     32                                  uint8_t* requested_begin) {
     33   capacity = RoundUp(capacity, kRegionSize);
     34   std::string error_msg;
     35   std::unique_ptr<MemMap> mem_map(MemMap::MapAnonymous(name.c_str(), requested_begin, capacity,
     36                                                        PROT_READ | PROT_WRITE, true, false,
     37                                                        &error_msg));
     38   if (mem_map.get() == nullptr) {
     39     LOG(ERROR) << "Failed to allocate pages for alloc space (" << name << ") of size "
     40         << PrettySize(capacity) << " with message " << error_msg;
     41     MemMap::DumpMaps(LOG(ERROR));
     42     return nullptr;
     43   }
     44   return new RegionSpace(name, mem_map.release());
     45 }
     46 
     47 RegionSpace::RegionSpace(const std::string& name, MemMap* mem_map)
     48     : ContinuousMemMapAllocSpace(name, mem_map, mem_map->Begin(), mem_map->End(), mem_map->End(),
     49                                  kGcRetentionPolicyAlwaysCollect),
     50       region_lock_("Region lock", kRegionSpaceRegionLock), time_(1U) {
     51   size_t mem_map_size = mem_map->Size();
     52   CHECK_ALIGNED(mem_map_size, kRegionSize);
     53   CHECK_ALIGNED(mem_map->Begin(), kRegionSize);
     54   num_regions_ = mem_map_size / kRegionSize;
     55   num_non_free_regions_ = 0U;
     56   DCHECK_GT(num_regions_, 0U);
     57   regions_.reset(new Region[num_regions_]);
     58   uint8_t* region_addr = mem_map->Begin();
     59   for (size_t i = 0; i < num_regions_; ++i, region_addr += kRegionSize) {
     60     regions_[i] = Region(i, region_addr, region_addr + kRegionSize);
     61   }
     62   if (kIsDebugBuild) {
     63     CHECK_EQ(regions_[0].Begin(), Begin());
     64     for (size_t i = 0; i < num_regions_; ++i) {
     65       CHECK(regions_[i].IsFree());
     66       CHECK_EQ(static_cast<size_t>(regions_[i].End() - regions_[i].Begin()), kRegionSize);
     67       if (i + 1 < num_regions_) {
     68         CHECK_EQ(regions_[i].End(), regions_[i + 1].Begin());
     69       }
     70     }
     71     CHECK_EQ(regions_[num_regions_ - 1].End(), Limit());
     72   }
     73   full_region_ = Region();
     74   DCHECK(!full_region_.IsFree());
     75   DCHECK(full_region_.IsAllocated());
     76   current_region_ = &full_region_;
     77   evac_region_ = nullptr;
     78   size_t ignored;
     79   DCHECK(full_region_.Alloc(kAlignment, &ignored, nullptr, &ignored) == nullptr);
     80 }
     81 
     82 size_t RegionSpace::FromSpaceSize() {
     83   uint64_t num_regions = 0;
     84   MutexLock mu(Thread::Current(), region_lock_);
     85   for (size_t i = 0; i < num_regions_; ++i) {
     86     Region* r = &regions_[i];
     87     if (r->IsInFromSpace()) {
     88       ++num_regions;
     89     }
     90   }
     91   return num_regions * kRegionSize;
     92 }
     93 
     94 size_t RegionSpace::UnevacFromSpaceSize() {
     95   uint64_t num_regions = 0;
     96   MutexLock mu(Thread::Current(), region_lock_);
     97   for (size_t i = 0; i < num_regions_; ++i) {
     98     Region* r = &regions_[i];
     99     if (r->IsInUnevacFromSpace()) {
    100       ++num_regions;
    101     }
    102   }
    103   return num_regions * kRegionSize;
    104 }
    105 
    106 size_t RegionSpace::ToSpaceSize() {
    107   uint64_t num_regions = 0;
    108   MutexLock mu(Thread::Current(), region_lock_);
    109   for (size_t i = 0; i < num_regions_; ++i) {
    110     Region* r = &regions_[i];
    111     if (r->IsInToSpace()) {
    112       ++num_regions;
    113     }
    114   }
    115   return num_regions * kRegionSize;
    116 }
    117 
    118 inline bool RegionSpace::Region::ShouldBeEvacuated() {
    119   DCHECK((IsAllocated() || IsLarge()) && IsInToSpace());
    120   // if the region was allocated after the start of the
    121   // previous GC or the live ratio is below threshold, evacuate
    122   // it.
    123   bool result;
    124   if (is_newly_allocated_) {
    125     result = true;
    126   } else {
    127     bool is_live_percent_valid = live_bytes_ != static_cast<size_t>(-1);
    128     if (is_live_percent_valid) {
    129       uint live_percent = GetLivePercent();
    130       if (IsAllocated()) {
    131         // Side node: live_percent == 0 does not necessarily mean
    132         // there's no live objects due to rounding (there may be a
    133         // few).
    134         result = live_percent < kEvaculateLivePercentThreshold;
    135       } else {
    136         DCHECK(IsLarge());
    137         result = live_percent == 0U;
    138       }
    139     } else {
    140       result = false;
    141     }
    142   }
    143   return result;
    144 }
    145 
    146 // Determine which regions to evacuate and mark them as
    147 // from-space. Mark the rest as unevacuated from-space.
    148 void RegionSpace::SetFromSpace(accounting::ReadBarrierTable* rb_table, bool force_evacuate_all) {
    149   ++time_;
    150   if (kUseTableLookupReadBarrier) {
    151     DCHECK(rb_table->IsAllCleared());
    152     rb_table->SetAll();
    153   }
    154   MutexLock mu(Thread::Current(), region_lock_);
    155   size_t num_expected_large_tails = 0;
    156   bool prev_large_evacuated = false;
    157   for (size_t i = 0; i < num_regions_; ++i) {
    158     Region* r = &regions_[i];
    159     RegionState state = r->State();
    160     RegionType type = r->Type();
    161     if (!r->IsFree()) {
    162       DCHECK(r->IsInToSpace());
    163       if (LIKELY(num_expected_large_tails == 0U)) {
    164         DCHECK((state == RegionState::kRegionStateAllocated ||
    165                 state == RegionState::kRegionStateLarge) &&
    166                type == RegionType::kRegionTypeToSpace);
    167         bool should_evacuate = force_evacuate_all || r->ShouldBeEvacuated();
    168         if (should_evacuate) {
    169           r->SetAsFromSpace();
    170           DCHECK(r->IsInFromSpace());
    171         } else {
    172           r->SetAsUnevacFromSpace();
    173           DCHECK(r->IsInUnevacFromSpace());
    174         }
    175         if (UNLIKELY(state == RegionState::kRegionStateLarge &&
    176                      type == RegionType::kRegionTypeToSpace)) {
    177           prev_large_evacuated = should_evacuate;
    178           num_expected_large_tails = RoundUp(r->BytesAllocated(), kRegionSize) / kRegionSize - 1;
    179           DCHECK_GT(num_expected_large_tails, 0U);
    180         }
    181       } else {
    182         DCHECK(state == RegionState::kRegionStateLargeTail &&
    183                type == RegionType::kRegionTypeToSpace);
    184         if (prev_large_evacuated) {
    185           r->SetAsFromSpace();
    186           DCHECK(r->IsInFromSpace());
    187         } else {
    188           r->SetAsUnevacFromSpace();
    189           DCHECK(r->IsInUnevacFromSpace());
    190         }
    191         --num_expected_large_tails;
    192       }
    193     } else {
    194       DCHECK_EQ(num_expected_large_tails, 0U);
    195       if (kUseTableLookupReadBarrier) {
    196         // Clear the rb table for to-space regions.
    197         rb_table->Clear(r->Begin(), r->End());
    198       }
    199     }
    200   }
    201   current_region_ = &full_region_;
    202   evac_region_ = &full_region_;
    203 }
    204 
    205 void RegionSpace::ClearFromSpace() {
    206   MutexLock mu(Thread::Current(), region_lock_);
    207   for (size_t i = 0; i < num_regions_; ++i) {
    208     Region* r = &regions_[i];
    209     if (r->IsInFromSpace()) {
    210       r->Clear();
    211       --num_non_free_regions_;
    212     } else if (r->IsInUnevacFromSpace()) {
    213       r->SetUnevacFromSpaceAsToSpace();
    214     }
    215   }
    216   evac_region_ = nullptr;
    217 }
    218 
    219 void RegionSpace::AssertAllRegionLiveBytesZeroOrCleared() {
    220   if (kIsDebugBuild) {
    221     MutexLock mu(Thread::Current(), region_lock_);
    222     for (size_t i = 0; i < num_regions_; ++i) {
    223       Region* r = &regions_[i];
    224       size_t live_bytes = r->LiveBytes();
    225       CHECK(live_bytes == 0U || live_bytes == static_cast<size_t>(-1)) << live_bytes;
    226     }
    227   }
    228 }
    229 
    230 void RegionSpace::LogFragmentationAllocFailure(std::ostream& os,
    231                                                size_t /* failed_alloc_bytes */) {
    232   size_t max_contiguous_allocation = 0;
    233   MutexLock mu(Thread::Current(), region_lock_);
    234   if (current_region_->End() - current_region_->Top() > 0) {
    235     max_contiguous_allocation = current_region_->End() - current_region_->Top();
    236   }
    237   if (num_non_free_regions_ * 2 < num_regions_) {
    238     // We reserve half of the regions for evaluation only. If we
    239     // occupy more than half the regions, do not report the free
    240     // regions as available.
    241     size_t max_contiguous_free_regions = 0;
    242     size_t num_contiguous_free_regions = 0;
    243     bool prev_free_region = false;
    244     for (size_t i = 0; i < num_regions_; ++i) {
    245       Region* r = &regions_[i];
    246       if (r->IsFree()) {
    247         if (!prev_free_region) {
    248           CHECK_EQ(num_contiguous_free_regions, 0U);
    249           prev_free_region = true;
    250         }
    251         ++num_contiguous_free_regions;
    252       } else {
    253         if (prev_free_region) {
    254           CHECK_NE(num_contiguous_free_regions, 0U);
    255           max_contiguous_free_regions = std::max(max_contiguous_free_regions,
    256                                                  num_contiguous_free_regions);
    257           num_contiguous_free_regions = 0U;
    258           prev_free_region = false;
    259         }
    260       }
    261     }
    262     max_contiguous_allocation = std::max(max_contiguous_allocation,
    263                                          max_contiguous_free_regions * kRegionSize);
    264   }
    265   os << "; failed due to fragmentation (largest possible contiguous allocation "
    266      <<  max_contiguous_allocation << " bytes)";
    267   // Caller's job to print failed_alloc_bytes.
    268 }
    269 
    270 void RegionSpace::Clear() {
    271   MutexLock mu(Thread::Current(), region_lock_);
    272   for (size_t i = 0; i < num_regions_; ++i) {
    273     Region* r = &regions_[i];
    274     if (!r->IsFree()) {
    275       --num_non_free_regions_;
    276     }
    277     r->Clear();
    278   }
    279   current_region_ = &full_region_;
    280   evac_region_ = &full_region_;
    281 }
    282 
    283 void RegionSpace::Dump(std::ostream& os) const {
    284   os << GetName() << " "
    285       << reinterpret_cast<void*>(Begin()) << "-" << reinterpret_cast<void*>(Limit());
    286 }
    287 
    288 void RegionSpace::FreeLarge(mirror::Object* large_obj, size_t bytes_allocated) {
    289   DCHECK(Contains(large_obj));
    290   DCHECK_ALIGNED(large_obj, kRegionSize);
    291   MutexLock mu(Thread::Current(), region_lock_);
    292   uint8_t* begin_addr = reinterpret_cast<uint8_t*>(large_obj);
    293   uint8_t* end_addr = AlignUp(reinterpret_cast<uint8_t*>(large_obj) + bytes_allocated, kRegionSize);
    294   CHECK_LT(begin_addr, end_addr);
    295   for (uint8_t* addr = begin_addr; addr < end_addr; addr += kRegionSize) {
    296     Region* reg = RefToRegionLocked(reinterpret_cast<mirror::Object*>(addr));
    297     if (addr == begin_addr) {
    298       DCHECK(reg->IsLarge());
    299     } else {
    300       DCHECK(reg->IsLargeTail());
    301     }
    302     reg->Clear();
    303     --num_non_free_regions_;
    304   }
    305   if (end_addr < Limit()) {
    306     // If we aren't at the end of the space, check that the next region is not a large tail.
    307     Region* following_reg = RefToRegionLocked(reinterpret_cast<mirror::Object*>(end_addr));
    308     DCHECK(!following_reg->IsLargeTail());
    309   }
    310 }
    311 
    312 void RegionSpace::DumpRegions(std::ostream& os) {
    313   MutexLock mu(Thread::Current(), region_lock_);
    314   for (size_t i = 0; i < num_regions_; ++i) {
    315     regions_[i].Dump(os);
    316   }
    317 }
    318 
    319 void RegionSpace::DumpNonFreeRegions(std::ostream& os) {
    320   MutexLock mu(Thread::Current(), region_lock_);
    321   for (size_t i = 0; i < num_regions_; ++i) {
    322     Region* reg = &regions_[i];
    323     if (!reg->IsFree()) {
    324       reg->Dump(os);
    325     }
    326   }
    327 }
    328 
    329 void RegionSpace::RecordAlloc(mirror::Object* ref) {
    330   CHECK(ref != nullptr);
    331   Region* r = RefToRegion(ref);
    332   reinterpret_cast<Atomic<uint64_t>*>(&r->objects_allocated_)->FetchAndAddSequentiallyConsistent(1);
    333 }
    334 
    335 bool RegionSpace::AllocNewTlab(Thread* self) {
    336   MutexLock mu(self, region_lock_);
    337   RevokeThreadLocalBuffersLocked(self);
    338   // Retain sufficient free regions for full evacuation.
    339   if ((num_non_free_regions_ + 1) * 2 > num_regions_) {
    340     return false;
    341   }
    342   for (size_t i = 0; i < num_regions_; ++i) {
    343     Region* r = &regions_[i];
    344     if (r->IsFree()) {
    345       r->Unfree(time_);
    346       ++num_non_free_regions_;
    347       // TODO: this is buggy. Debug it.
    348       // r->SetNewlyAllocated();
    349       r->SetTop(r->End());
    350       r->is_a_tlab_ = true;
    351       r->thread_ = self;
    352       self->SetTlab(r->Begin(), r->End());
    353       return true;
    354     }
    355   }
    356   return false;
    357 }
    358 
    359 size_t RegionSpace::RevokeThreadLocalBuffers(Thread* thread) {
    360   MutexLock mu(Thread::Current(), region_lock_);
    361   RevokeThreadLocalBuffersLocked(thread);
    362   return 0U;
    363 }
    364 
    365 void RegionSpace::RevokeThreadLocalBuffersLocked(Thread* thread) {
    366   uint8_t* tlab_start = thread->GetTlabStart();
    367   DCHECK_EQ(thread->HasTlab(), tlab_start != nullptr);
    368   if (tlab_start != nullptr) {
    369     DCHECK_ALIGNED(tlab_start, kRegionSize);
    370     Region* r = RefToRegionLocked(reinterpret_cast<mirror::Object*>(tlab_start));
    371     DCHECK(r->IsAllocated());
    372     DCHECK_EQ(thread->GetThreadLocalBytesAllocated(), kRegionSize);
    373     r->RecordThreadLocalAllocations(thread->GetThreadLocalObjectsAllocated(),
    374                                     thread->GetThreadLocalBytesAllocated());
    375     r->is_a_tlab_ = false;
    376     r->thread_ = nullptr;
    377   }
    378   thread->SetTlab(nullptr, nullptr);
    379 }
    380 
    381 size_t RegionSpace::RevokeAllThreadLocalBuffers() {
    382   Thread* self = Thread::Current();
    383   MutexLock mu(self, *Locks::runtime_shutdown_lock_);
    384   MutexLock mu2(self, *Locks::thread_list_lock_);
    385   std::list<Thread*> thread_list = Runtime::Current()->GetThreadList()->GetList();
    386   for (Thread* thread : thread_list) {
    387     RevokeThreadLocalBuffers(thread);
    388   }
    389   return 0U;
    390 }
    391 
    392 void RegionSpace::AssertThreadLocalBuffersAreRevoked(Thread* thread) {
    393   if (kIsDebugBuild) {
    394     DCHECK(!thread->HasTlab());
    395   }
    396 }
    397 
    398 void RegionSpace::AssertAllThreadLocalBuffersAreRevoked() {
    399   if (kIsDebugBuild) {
    400     Thread* self = Thread::Current();
    401     MutexLock mu(self, *Locks::runtime_shutdown_lock_);
    402     MutexLock mu2(self, *Locks::thread_list_lock_);
    403     std::list<Thread*> thread_list = Runtime::Current()->GetThreadList()->GetList();
    404     for (Thread* thread : thread_list) {
    405       AssertThreadLocalBuffersAreRevoked(thread);
    406     }
    407   }
    408 }
    409 
    410 void RegionSpace::Region::Dump(std::ostream& os) const {
    411   os << "Region[" << idx_ << "]=" << reinterpret_cast<void*>(begin_) << "-" << reinterpret_cast<void*>(top_)
    412      << "-" << reinterpret_cast<void*>(end_)
    413      << " state=" << static_cast<uint>(state_) << " type=" << static_cast<uint>(type_)
    414      << " objects_allocated=" << objects_allocated_
    415      << " alloc_time=" << alloc_time_ << " live_bytes=" << live_bytes_
    416      << " is_newly_allocated=" << is_newly_allocated_ << " is_a_tlab=" << is_a_tlab_ << " thread=" << thread_ << "\n";
    417 }
    418 
    419 }  // namespace space
    420 }  // namespace gc
    421 }  // namespace art
    422