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rocksdb/util/file_reader_writer.cc

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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#include "util/file_reader_writer.h"
#include <algorithm>
#include <mutex>
#include "port/port.h"
#include "util/histogram.h"
#include "util/iostats_context_imp.h"
#include "util/random.h"
#include "util/rate_limiter.h"
#include "util/sync_point.h"
namespace rocksdb {
Status SequentialFileReader::Read(size_t n, Slice* result, char* scratch) {
Status s = file_->Read(n, result, scratch);
IOSTATS_ADD(bytes_read, result->size());
return s;
}
Status SequentialFileReader::Skip(uint64_t n) { return file_->Skip(n); }
Status RandomAccessFileReader::Read(uint64_t offset, size_t n, Slice* result,
char* scratch) const {
Status s;
uint64_t elapsed = 0;
{
StopWatch sw(env_, stats_, hist_type_,
(stats_ != nullptr) ? &elapsed : nullptr);
IOSTATS_TIMER_GUARD(read_nanos);
s = file_->Read(offset, n, result, scratch);
IOSTATS_ADD_IF_POSITIVE(bytes_read, result->size());
}
if (stats_ != nullptr && file_read_hist_ != nullptr) {
file_read_hist_->Add(elapsed);
}
return s;
}
Status WritableFileWriter::Append(const Slice& data) {
const char* src = data.data();
size_t left = data.size();
Status s;
pending_sync_ = true;
pending_fsync_ = true;
TEST_KILL_RANDOM(rocksdb_kill_odds * REDUCE_ODDS2);
{
IOSTATS_TIMER_GUARD(prepare_write_nanos);
TEST_SYNC_POINT("WritableFileWriter::Append:BeforePrepareWrite");
writable_file_->PrepareWrite(static_cast<size_t>(GetFileSize()), left);
}
// if there is no space in the cache, then flush
if (cursize_ + left > capacity_) {
s = Flush();
if (!s.ok()) {
return s;
}
// Increase the buffer size, but capped at 1MB
if (capacity_ < (1 << 20)) {
capacity_ *= 2;
buf_.reset(new char[capacity_]);
}
assert(cursize_ == 0);
}
// if the write fits into the cache, then write to cache
// otherwise do a write() syscall to write to OS buffers.
if (cursize_ + left <= capacity_) {
memcpy(buf_.get() + cursize_, src, left);
cursize_ += left;
} else {
while (left != 0) {
size_t size = RequestToken(left);
{
IOSTATS_TIMER_GUARD(write_nanos);
s = writable_file_->Append(Slice(src, size));
if (!s.ok()) {
return s;
}
}
IOSTATS_ADD(bytes_written, size);
TEST_KILL_RANDOM(rocksdb_kill_odds);
left -= size;
src += size;
}
}
TEST_KILL_RANDOM(rocksdb_kill_odds);
filesize_ += data.size();
return Status::OK();
}
Status WritableFileWriter::Close() {
Status s;
s = Flush(); // flush cache to OS
if (!s.ok()) {
return s;
}
TEST_KILL_RANDOM(rocksdb_kill_odds);
return writable_file_->Close();
}
// write out the cached data to the OS cache
Status WritableFileWriter::Flush() {
TEST_KILL_RANDOM(rocksdb_kill_odds * REDUCE_ODDS2);
size_t left = cursize_;
char* src = buf_.get();
while (left != 0) {
size_t size = RequestToken(left);
{
IOSTATS_TIMER_GUARD(write_nanos);
TEST_SYNC_POINT("WritableFileWriter::Flush:BeforeAppend");
Status s = writable_file_->Append(Slice(src, size));
if (!s.ok()) {
return s;
}
}
IOSTATS_ADD(bytes_written, size);
TEST_KILL_RANDOM(rocksdb_kill_odds * REDUCE_ODDS2);
left -= size;
src += size;
}
cursize_ = 0;
writable_file_->Flush();
// sync OS cache to disk for every bytes_per_sync_
// TODO: give log file and sst file different options (log
// files could be potentially cached in OS for their whole
// life time, thus we might not want to flush at all).
// We try to avoid sync to the last 1MB of data. For two reasons:
// (1) avoid rewrite the same page that is modified later.
// (2) for older version of OS, write can block while writing out
// the page.
// Xfs does neighbor page flushing outside of the specified ranges. We
// need to make sure sync range is far from the write offset.
if (bytes_per_sync_) {
uint64_t kBytesNotSyncRange = 1024 * 1024; // recent 1MB is not synced.
uint64_t kBytesAlignWhenSync = 4 * 1024; // Align 4KB.
if (filesize_ > kBytesNotSyncRange) {
uint64_t offset_sync_to = filesize_ - kBytesNotSyncRange;
offset_sync_to -= offset_sync_to % kBytesAlignWhenSync;
assert(offset_sync_to >= last_sync_size_);
if (offset_sync_to > 0 &&
offset_sync_to - last_sync_size_ >= bytes_per_sync_) {
RangeSync(last_sync_size_, offset_sync_to - last_sync_size_);
last_sync_size_ = offset_sync_to;
}
}
}
return Status::OK();
}
Status WritableFileWriter::Sync(bool use_fsync) {
Status s = Flush();
if (!s.ok()) {
return s;
}
TEST_KILL_RANDOM(rocksdb_kill_odds);
if (pending_sync_) {
s = SyncInternal(use_fsync);
if (!s.ok()) {
return s;
}
}
TEST_KILL_RANDOM(rocksdb_kill_odds);
pending_sync_ = false;
if (use_fsync) {
pending_fsync_ = false;
}
return Status::OK();
}
Status WritableFileWriter::SyncWithoutFlush(bool use_fsync) {
if (!writable_file_->IsSyncThreadSafe()) {
return Status::NotSupported(
"Can't WritableFileWriter::SyncWithoutFlush() because "
"WritableFile::IsSyncThreadSafe() is false");
}
TEST_SYNC_POINT("WritableFileWriter::SyncWithoutFlush:1");
Status s = SyncInternal(use_fsync);
TEST_SYNC_POINT("WritableFileWriter::SyncWithoutFlush:2");
return s;
}
Status WritableFileWriter::SyncInternal(bool use_fsync) {
Status s;
IOSTATS_TIMER_GUARD(fsync_nanos);
TEST_SYNC_POINT("WritableFileWriter::SyncInternal:0");
if (use_fsync) {
s = writable_file_->Fsync();
} else {
s = writable_file_->Sync();
}
return s;
}
Status WritableFileWriter::RangeSync(off_t offset, off_t nbytes) {
IOSTATS_TIMER_GUARD(range_sync_nanos);
TEST_SYNC_POINT("WritableFileWriter::RangeSync:0");
return writable_file_->RangeSync(offset, nbytes);
}
size_t WritableFileWriter::RequestToken(size_t bytes) {
Env::IOPriority io_priority;
if (rate_limiter_&&(io_priority = writable_file_->GetIOPriority()) <
Env::IO_TOTAL) {
bytes = std::min(bytes,
static_cast<size_t>(rate_limiter_->GetSingleBurstBytes()));
rate_limiter_->Request(bytes, io_priority);
}
return bytes;
}
namespace {
class ReadaheadRandomAccessFile : public RandomAccessFile {
public:
ReadaheadRandomAccessFile(std::unique_ptr<RandomAccessFile> file,
size_t readahead_size)
: file_(std::move(file)),
readahead_size_(readahead_size),
buffer_(new char[readahead_size_]),
buffer_offset_(0),
buffer_len_(0) {}
virtual Status Read(uint64_t offset, size_t n, Slice* result,
char* scratch) const override {
if (n >= readahead_size_) {
return file_->Read(offset, n, result, scratch);
}
std::unique_lock<std::mutex> lk(lock_);
size_t copied = 0;
// if offset between [buffer_offset_, buffer_offset_ + buffer_len>
if (offset >= buffer_offset_ && offset < buffer_len_ + buffer_offset_) {
uint64_t offset_in_buffer = offset - buffer_offset_;
copied = std::min(static_cast<uint64_t>(buffer_len_) - offset_in_buffer,
static_cast<uint64_t>(n));
memcpy(scratch, buffer_.get() + offset_in_buffer, copied);
if (copied == n) {
// fully cached
*result = Slice(scratch, n);
return Status::OK();
}
}
Slice readahead_result;
Status s = file_->Read(offset + copied, readahead_size_, &readahead_result,
buffer_.get());
if (!s.ok()) {
return s;
}
auto left_to_copy = std::min(readahead_result.size(), n - copied);
memcpy(scratch + copied, readahead_result.data(), left_to_copy);
*result = Slice(scratch, copied + left_to_copy);
if (readahead_result.data() == buffer_.get()) {
buffer_offset_ = offset + copied;
buffer_len_ = readahead_result.size();
} else {
buffer_len_ = 0;
}
return Status::OK();
}
virtual size_t GetUniqueId(char* id, size_t max_size) const override {
return file_->GetUniqueId(id, max_size);
}
virtual void Hint(AccessPattern pattern) override { file_->Hint(pattern); }
virtual Status InvalidateCache(size_t offset, size_t length) override {
return file_->InvalidateCache(offset, length);
}
private:
std::unique_ptr<RandomAccessFile> file_;
size_t readahead_size_;
mutable std::mutex lock_;
mutable std::unique_ptr<char[]> buffer_;
mutable uint64_t buffer_offset_;
mutable size_t buffer_len_;
};
} // namespace
std::unique_ptr<RandomAccessFile> NewReadaheadRandomAccessFile(
std::unique_ptr<RandomAccessFile> file, size_t readahead_size) {
std::unique_ptr<ReadaheadRandomAccessFile> wrapped_file(
new ReadaheadRandomAccessFile(std::move(file), readahead_size));
return std::move(wrapped_file);
}
} // namespace rocksdb