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/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ART_RUNTIME_GC_ACCOUNTING_READ_BARRIER_TABLE_H_
#define ART_RUNTIME_GC_ACCOUNTING_READ_BARRIER_TABLE_H_
#include <sys/mman.h> // For the PROT_* and MAP_* constants.
#include <cstring>
#include "base/bit_utils.h"
#include "base/locks.h"
#include "base/mem_map.h"
#include "gc/space/space.h"
#include "runtime_globals.h"
namespace art {
namespace gc {
namespace accounting {
// Used to decide whether to take the read barrier fast/slow paths for
// kUseTableLookupReadBarrier. If an entry is set, take the read
// barrier slow path. There's an entry per region.
class ReadBarrierTable {
public:
ReadBarrierTable() {
size_t capacity = static_cast<size_t>(kHeapCapacity / kRegionSize);
DCHECK_EQ(kHeapCapacity / kRegionSize,
static_cast<uint64_t>(static_cast<size_t>(kHeapCapacity / kRegionSize)));
std::string error_msg;
mem_map_ = MemMap::MapAnonymous("read barrier table",
capacity,
PROT_READ | PROT_WRITE,
/*low_4gb=*/ false,
&error_msg);
CHECK(mem_map_.IsValid() && mem_map_.Begin() != nullptr)
<< "couldn't allocate read barrier table: " << error_msg;
}
void ClearForSpace(space::ContinuousSpace* space) {
uint8_t* entry_start = EntryFromAddr(space->Begin());
uint8_t* entry_end = EntryFromAddr(space->Limit());
memset(reinterpret_cast<void*>(entry_start), 0, entry_end - entry_start);
}
void Clear(uint8_t* start_addr, uint8_t* end_addr) {
DCHECK(IsValidHeapAddr(start_addr)) << start_addr;
DCHECK(IsValidHeapAddr(end_addr)) << end_addr;
DCHECK_ALIGNED(start_addr, kRegionSize);
DCHECK_ALIGNED(end_addr, kRegionSize);
uint8_t* entry_start = EntryFromAddr(start_addr);
uint8_t* entry_end = EntryFromAddr(end_addr);
memset(reinterpret_cast<void*>(entry_start), 0, entry_end - entry_start);
}
bool IsSet(const void* heap_addr) const {
DCHECK(IsValidHeapAddr(heap_addr)) << heap_addr;
uint8_t entry_value = *EntryFromAddr(heap_addr);
DCHECK(entry_value == 0 || entry_value == kSetEntryValue);
return entry_value == kSetEntryValue;
}
void ClearAll() {
mem_map_.MadviseDontNeedAndZero();
}
void SetAll() {
memset(mem_map_.Begin(), kSetEntryValue, mem_map_.Size());
}
bool IsAllCleared() const {
for (uint32_t* p = reinterpret_cast<uint32_t*>(mem_map_.Begin());
p < reinterpret_cast<uint32_t*>(mem_map_.End()); ++p) {
if (*p != 0) {
return false;
}
}
return true;
}
// This should match RegionSpace::kRegionSize. static_assert'ed in concurrent_copying.h.
static constexpr size_t kRegionSize = 256 * KB;
private:
static constexpr uint64_t kHeapCapacity = 4ULL * GB; // low 4gb.
static constexpr uint8_t kSetEntryValue = 0x01;
uint8_t* EntryFromAddr(const void* heap_addr) const {
DCHECK(IsValidHeapAddr(heap_addr)) << heap_addr;
uint8_t* entry_addr = mem_map_.Begin() + reinterpret_cast<uintptr_t>(heap_addr) / kRegionSize;
DCHECK(IsValidEntry(entry_addr)) << "heap_addr: " << heap_addr
<< " entry_addr: " << reinterpret_cast<void*>(entry_addr);
return entry_addr;
}
bool IsValidHeapAddr(const void* heap_addr) const {
#ifdef __LP64__
return reinterpret_cast<uint64_t>(heap_addr) < kHeapCapacity;
#else
UNUSED(heap_addr);
return true;
#endif
}
bool IsValidEntry(const uint8_t* entry_addr) const {
uint8_t* begin = mem_map_.Begin();
uint8_t* end = mem_map_.End();
return entry_addr >= begin && entry_addr < end;
}
MemMap mem_map_;
};
} // namespace accounting
} // namespace gc
} // namespace art
#endif // ART_RUNTIME_GC_ACCOUNTING_READ_BARRIER_TABLE_H_
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