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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.
*/
#include "swap_space.h"
#include <sys/mman.h>
#include <algorithm>
#include <numeric>
#include "base/bit_utils.h"
#include "base/macros.h"
#include "base/mutex.h"
#include "thread-current-inl.h"
namespace art {
// The chunk size by which the swap file is increased and mapped.
static constexpr size_t kMininumMapSize = 16 * MB;
static constexpr bool kCheckFreeMaps = false;
template <typename FreeBySizeSet>
static void DumpFreeMap(const FreeBySizeSet& free_by_size) {
size_t last_size = static_cast<size_t>(-1);
for (const auto& entry : free_by_size) {
if (last_size != entry.size) {
last_size = entry.size;
LOG(INFO) << "Size " << last_size;
}
LOG(INFO) << " 0x" << std::hex << entry.free_by_start_entry->Start()
<< " size=" << std::dec << entry.free_by_start_entry->size;
}
}
void SwapSpace::RemoveChunk(FreeBySizeSet::const_iterator free_by_size_pos) {
auto free_by_start_pos = free_by_size_pos->free_by_start_entry;
free_by_size_.erase(free_by_size_pos);
free_by_start_.erase(free_by_start_pos);
}
inline void SwapSpace::InsertChunk(const SpaceChunk& chunk) {
DCHECK_NE(chunk.size, 0u);
auto insert_result = free_by_start_.insert(chunk);
DCHECK(insert_result.second);
free_by_size_.emplace(chunk.size, insert_result.first);
}
SwapSpace::SwapSpace(int fd, size_t initial_size)
: fd_(fd),
size_(0),
lock_("SwapSpace lock", static_cast<LockLevel>(LockLevel::kDefaultMutexLevel - 1)) {
// Assume that the file is unlinked.
InsertChunk(NewFileChunk(initial_size));
}
SwapSpace::~SwapSpace() {
// Unmap all mmapped chunks. Nothing should be allocated anymore at
// this point, so there should be only full size chunks in free_by_start_.
for (const SpaceChunk& chunk : free_by_start_) {
if (munmap(chunk.ptr, chunk.size) != 0) {
PLOG(ERROR) << "Failed to unmap swap space chunk at "
<< static_cast<const void*>(chunk.ptr) << " size=" << chunk.size;
}
}
// All arenas are backed by the same file. Just close the descriptor.
close(fd_);
}
template <typename FreeByStartSet, typename FreeBySizeSet>
static size_t CollectFree(const FreeByStartSet& free_by_start, const FreeBySizeSet& free_by_size) {
if (free_by_start.size() != free_by_size.size()) {
LOG(FATAL) << "Size: " << free_by_start.size() << " vs " << free_by_size.size();
}
// Calculate over free_by_size.
size_t sum1 = 0;
for (const auto& entry : free_by_size) {
sum1 += entry.free_by_start_entry->size;
}
// Calculate over free_by_start.
size_t sum2 = 0;
for (const auto& entry : free_by_start) {
sum2 += entry.size;
}
if (sum1 != sum2) {
LOG(FATAL) << "Sum: " << sum1 << " vs " << sum2;
}
return sum1;
}
void* SwapSpace::Alloc(size_t size) {
MutexLock lock(Thread::Current(), lock_);
size = RoundUp(size, 8U);
// Check the free list for something that fits.
// TODO: Smarter implementation. Global biggest chunk, ...
auto it = free_by_start_.empty()
? free_by_size_.end()
: free_by_size_.lower_bound(FreeBySizeEntry { size, free_by_start_.begin() });
if (it != free_by_size_.end()) {
auto entry = it->free_by_start_entry;
SpaceChunk old_chunk = *entry;
if (old_chunk.size == size) {
RemoveChunk(it);
} else {
// Try to avoid deallocating and allocating the std::set<> nodes.
// This would be much simpler if we could use replace() from Boost.Bimap.
// The free_by_start_ map contains disjoint intervals ordered by the `ptr`.
// Shrinking the interval does not affect the ordering.
it->free_by_start_entry->ptr += size;
it->free_by_start_entry->size -= size;
// The free_by_size_ map is ordered by the `size` and then `free_by_start_entry->ptr`.
// Adjusting the `ptr` above does not change that ordering but decreasing `size` can
// push the node before the previous node(s).
if (it == free_by_size_.begin()) {
it->size -= size;
} else {
auto prev = it;
--prev;
FreeBySizeEntry new_value(old_chunk.size - size, entry);
if (free_by_size_.key_comp()(*prev, new_value)) {
it->size -= size;
} else {
// Changing in place would break the std::set<> ordering, we need to remove and insert.
// TODO: When C++17 becomes available, use std::map<>::extract(), modify, insert.
free_by_size_.erase(it);
free_by_size_.insert(new_value);
}
}
}
return old_chunk.ptr;
} else {
// Not a big enough free chunk, need to increase file size.
SpaceChunk new_chunk = NewFileChunk(size);
if (new_chunk.size != size) {
// Insert the remainder.
SpaceChunk remainder = { new_chunk.ptr + size, new_chunk.size - size };
InsertChunk(remainder);
}
return new_chunk.ptr;
}
}
SwapSpace::SpaceChunk SwapSpace::NewFileChunk(size_t min_size) {
#if !defined(__APPLE__)
size_t next_part = std::max(RoundUp(min_size, kPageSize), RoundUp(kMininumMapSize, kPageSize));
int result = TEMP_FAILURE_RETRY(ftruncate64(fd_, size_ + next_part));
if (result != 0) {
PLOG(FATAL) << "Unable to increase swap file.";
}
uint8_t* ptr = reinterpret_cast<uint8_t*>(
mmap(nullptr, next_part, PROT_READ | PROT_WRITE, MAP_SHARED, fd_, size_));
if (ptr == MAP_FAILED) {
LOG(ERROR) << "Unable to mmap new swap file chunk.";
LOG(ERROR) << "Current size: " << size_ << " requested: " << next_part << "/" << min_size;
LOG(ERROR) << "Free list:";
DumpFreeMap(free_by_size_);
LOG(ERROR) << "In free list: " << CollectFree(free_by_start_, free_by_size_);
LOG(FATAL) << "Aborting...";
}
size_ += next_part;
SpaceChunk new_chunk = {ptr, next_part};
return new_chunk;
#else
UNUSED(min_size, kMininumMapSize);
LOG(FATAL) << "No swap file support on the Mac.";
UNREACHABLE();
#endif
}
// TODO: Full coalescing.
void SwapSpace::Free(void* ptr, size_t size) {
MutexLock lock(Thread::Current(), lock_);
size = RoundUp(size, 8U);
size_t free_before = 0;
if (kCheckFreeMaps) {
free_before = CollectFree(free_by_start_, free_by_size_);
}
SpaceChunk chunk = { reinterpret_cast<uint8_t*>(ptr), size };
auto it = free_by_start_.lower_bound(chunk);
if (it != free_by_start_.begin()) {
auto prev = it;
--prev;
CHECK_LE(prev->End(), chunk.Start());
if (prev->End() == chunk.Start()) {
// Merge *prev with this chunk.
chunk.size += prev->size;
chunk.ptr -= prev->size;
auto erase_pos = free_by_size_.find(FreeBySizeEntry { prev->size, prev });
DCHECK(erase_pos != free_by_size_.end());
RemoveChunk(erase_pos);
// "prev" is invalidated but "it" remains valid.
}
}
if (it != free_by_start_.end()) {
CHECK_LE(chunk.End(), it->Start());
if (chunk.End() == it->Start()) {
// Merge *it with this chunk.
chunk.size += it->size;
auto erase_pos = free_by_size_.find(FreeBySizeEntry { it->size, it });
DCHECK(erase_pos != free_by_size_.end());
RemoveChunk(erase_pos);
// "it" is invalidated but we don't need it anymore.
}
}
InsertChunk(chunk);
if (kCheckFreeMaps) {
size_t free_after = CollectFree(free_by_start_, free_by_size_);
if (free_after != free_before + size) {
DumpFreeMap(free_by_size_);
CHECK_EQ(free_after, free_before + size) << "Should be " << size << " difference from " << free_before;
}
}
}
} // namespace art