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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 #ifndef ART_RUNTIME_GC_ACCOUNTING_READ_BARRIER_TABLE_H_
     18 #define ART_RUNTIME_GC_ACCOUNTING_READ_BARRIER_TABLE_H_
     19 
     20 #include "base/bit_utils.h"
     21 #include "base/mutex.h"
     22 #include "gc/space/space.h"
     23 #include "globals.h"
     24 #include "mem_map.h"
     25 
     26 namespace art {
     27 namespace gc {
     28 namespace accounting {
     29 
     30 // Used to decide whether to take the read barrier fast/slow paths for
     31 // kUseTableLookupReadBarrier. If an entry is set, take the read
     32 // barrier slow path. There's an entry per region.
     33 class ReadBarrierTable {
     34  public:
     35   ReadBarrierTable() {
     36     size_t capacity = static_cast<size_t>(kHeapCapacity / kRegionSize);
     37     DCHECK_EQ(kHeapCapacity / kRegionSize,
     38               static_cast<uint64_t>(static_cast<size_t>(kHeapCapacity / kRegionSize)));
     39     std::string error_msg;
     40     MemMap* mem_map = MemMap::MapAnonymous("read barrier table", nullptr, capacity,
     41                                            PROT_READ | PROT_WRITE, false, false, &error_msg);
     42     CHECK(mem_map != nullptr && mem_map->Begin() != nullptr)
     43         << "couldn't allocate read barrier table: " << error_msg;
     44     mem_map_.reset(mem_map);
     45   }
     46   void ClearForSpace(space::ContinuousSpace* space) {
     47     uint8_t* entry_start = EntryFromAddr(space->Begin());
     48     uint8_t* entry_end = EntryFromAddr(space->Limit());
     49     memset(reinterpret_cast<void*>(entry_start), 0, entry_end - entry_start);
     50   }
     51   void Clear(uint8_t* start_addr, uint8_t* end_addr) {
     52     DCHECK(IsValidHeapAddr(start_addr)) << start_addr;
     53     DCHECK(IsValidHeapAddr(end_addr)) << end_addr;
     54     DCHECK(IsAligned<kRegionSize>(start_addr));
     55     DCHECK(IsAligned<kRegionSize>(end_addr));
     56     uint8_t* entry_start = EntryFromAddr(start_addr);
     57     uint8_t* entry_end = EntryFromAddr(end_addr);
     58     memset(reinterpret_cast<void*>(entry_start), 0, entry_end - entry_start);
     59   }
     60   bool IsSet(const void* heap_addr) const {
     61     DCHECK(IsValidHeapAddr(heap_addr)) << heap_addr;
     62     uint8_t entry_value = *EntryFromAddr(heap_addr);
     63     DCHECK(entry_value == 0 || entry_value == kSetEntryValue);
     64     return entry_value == kSetEntryValue;
     65   }
     66   void ClearAll() {
     67     mem_map_->MadviseDontNeedAndZero();
     68   }
     69   void SetAll() {
     70     memset(mem_map_->Begin(), kSetEntryValue, mem_map_->Size());
     71   }
     72   bool IsAllCleared() const {
     73     for (uint32_t* p = reinterpret_cast<uint32_t*>(mem_map_->Begin());
     74          p < reinterpret_cast<uint32_t*>(mem_map_->End()); ++p) {
     75       if (*p != 0) {
     76         return false;
     77       }
     78     }
     79     return true;
     80   }
     81 
     82   // This should match RegionSpace::kRegionSize. static_assert'ed in concurrent_copying.h.
     83   static constexpr size_t kRegionSize = 1 * MB;
     84 
     85  private:
     86   static constexpr uint64_t kHeapCapacity = 4ULL * GB;  // low 4gb.
     87   static constexpr uint8_t kSetEntryValue = 0x01;
     88 
     89   uint8_t* EntryFromAddr(const void* heap_addr) const {
     90     DCHECK(IsValidHeapAddr(heap_addr)) << heap_addr;
     91     uint8_t* entry_addr = mem_map_->Begin() + reinterpret_cast<uintptr_t>(heap_addr) / kRegionSize;
     92     DCHECK(IsValidEntry(entry_addr)) << "heap_addr: " << heap_addr
     93                                      << " entry_addr: " << reinterpret_cast<void*>(entry_addr);
     94     return entry_addr;
     95   }
     96 
     97   bool IsValidHeapAddr(const void* heap_addr) const {
     98 #ifdef __LP64__
     99     return reinterpret_cast<uint64_t>(heap_addr) < kHeapCapacity;
    100 #else
    101     UNUSED(heap_addr);
    102     return true;
    103 #endif
    104   }
    105 
    106   bool IsValidEntry(const uint8_t* entry_addr) const {
    107     uint8_t* begin = mem_map_->Begin();
    108     uint8_t* end = mem_map_->End();
    109     return entry_addr >= begin && entry_addr < end;
    110   }
    111 
    112   std::unique_ptr<MemMap> mem_map_;
    113 };
    114 
    115 }  // namespace accounting
    116 }  // namespace gc
    117 }  // namespace art
    118 
    119 #endif  // ART_RUNTIME_GC_ACCOUNTING_READ_BARRIER_TABLE_H_
    120