6e8d6f429d
Summary: prefetch some data from the end of the file for each compaction to reduce IO. Closes https://github.com/facebook/rocksdb/pull/2149 Differential Revision: D4880576 Pulled By: lightmark fbshipit-source-id: aa767cd1afc84c541837fbf1ad6c0d45b34d3932
586 lines
18 KiB
C++
586 lines
18 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#include "util/file_reader_writer.h"
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#include <algorithm>
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#include <mutex>
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#include "monitoring/histogram.h"
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#include "monitoring/iostats_context_imp.h"
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#include "port/port.h"
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#include "util/random.h"
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#include "util/rate_limiter.h"
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#include "util/sync_point.h"
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namespace rocksdb {
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Status SequentialFileReader::Read(size_t n, Slice* result, char* scratch) {
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Status s;
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if (use_direct_io()) {
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#ifndef ROCKSDB_LITE
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size_t offset = offset_.fetch_add(n);
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size_t alignment = file_->GetRequiredBufferAlignment();
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size_t aligned_offset = TruncateToPageBoundary(alignment, offset);
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size_t offset_advance = offset - aligned_offset;
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size_t size = Roundup(offset + n, alignment) - aligned_offset;
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size_t r = 0;
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AlignedBuffer buf;
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buf.Alignment(alignment);
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buf.AllocateNewBuffer(size);
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Slice tmp;
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s = file_->PositionedRead(aligned_offset, size, &tmp, buf.BufferStart());
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if (s.ok() && offset_advance < tmp.size()) {
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buf.Size(tmp.size());
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r = buf.Read(scratch, offset_advance,
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std::min(tmp.size() - offset_advance, n));
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}
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*result = Slice(scratch, r);
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#endif // !ROCKSDB_LITE
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} else {
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s = file_->Read(n, result, scratch);
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}
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IOSTATS_ADD(bytes_read, result->size());
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return s;
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}
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Status SequentialFileReader::Skip(uint64_t n) {
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#ifndef ROCKSDB_LITE
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if (use_direct_io()) {
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offset_ += n;
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return Status::OK();
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}
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#endif // !ROCKSDB_LITE
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return file_->Skip(n);
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}
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Status RandomAccessFileReader::Read(uint64_t offset, size_t n, Slice* result,
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char* scratch) const {
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Status s;
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uint64_t elapsed = 0;
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{
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StopWatch sw(env_, stats_, hist_type_,
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(stats_ != nullptr) ? &elapsed : nullptr);
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IOSTATS_TIMER_GUARD(read_nanos);
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if (use_direct_io()) {
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#ifndef ROCKSDB_LITE
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size_t alignment = file_->GetRequiredBufferAlignment();
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size_t aligned_offset = TruncateToPageBoundary(alignment, offset);
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size_t offset_advance = offset - aligned_offset;
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size_t size = Roundup(offset + n, alignment) - aligned_offset;
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size_t r = 0;
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AlignedBuffer buf;
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buf.Alignment(alignment);
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buf.AllocateNewBuffer(size);
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Slice tmp;
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s = file_->Read(aligned_offset, size, &tmp, buf.BufferStart());
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if (s.ok() && offset_advance < tmp.size()) {
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buf.Size(tmp.size());
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r = buf.Read(scratch, offset_advance,
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std::min(tmp.size() - offset_advance, n));
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}
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*result = Slice(scratch, r);
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#endif // !ROCKSDB_LITE
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} else {
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s = file_->Read(offset, n, result, scratch);
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}
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IOSTATS_ADD_IF_POSITIVE(bytes_read, result->size());
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}
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if (stats_ != nullptr && file_read_hist_ != nullptr) {
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file_read_hist_->Add(elapsed);
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}
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return s;
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}
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Status WritableFileWriter::Append(const Slice& data) {
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const char* src = data.data();
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size_t left = data.size();
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Status s;
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pending_sync_ = true;
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TEST_KILL_RANDOM("WritableFileWriter::Append:0",
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rocksdb_kill_odds * REDUCE_ODDS2);
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{
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IOSTATS_TIMER_GUARD(prepare_write_nanos);
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TEST_SYNC_POINT("WritableFileWriter::Append:BeforePrepareWrite");
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writable_file_->PrepareWrite(static_cast<size_t>(GetFileSize()), left);
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}
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// Flush only when buffered I/O
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if (!use_direct_io() && (buf_.Capacity() - buf_.CurrentSize()) < left) {
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if (buf_.CurrentSize() > 0) {
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s = Flush();
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if (!s.ok()) {
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return s;
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}
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}
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if (buf_.Capacity() < max_buffer_size_) {
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size_t desiredCapacity = buf_.Capacity() * 2;
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desiredCapacity = std::min(desiredCapacity, max_buffer_size_);
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buf_.AllocateNewBuffer(desiredCapacity);
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}
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assert(buf_.CurrentSize() == 0);
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}
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// We never write directly to disk with direct I/O on.
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// or we simply use it for its original purpose to accumulate many small
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// chunks
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if (use_direct_io() || (buf_.Capacity() >= left)) {
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while (left > 0) {
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size_t appended = buf_.Append(src, left);
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left -= appended;
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src += appended;
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if (left > 0) {
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s = Flush();
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if (!s.ok()) {
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break;
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}
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// We double the buffer here because
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// Flush calls do not keep up with the incoming bytes
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// This is the only place when buffer is changed with direct I/O
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if (buf_.Capacity() < max_buffer_size_) {
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size_t desiredCapacity = buf_.Capacity() * 2;
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desiredCapacity = std::min(desiredCapacity, max_buffer_size_);
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buf_.AllocateNewBuffer(desiredCapacity);
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}
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}
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}
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} else {
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// Writing directly to file bypassing the buffer
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assert(buf_.CurrentSize() == 0);
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s = WriteBuffered(src, left);
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}
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TEST_KILL_RANDOM("WritableFileWriter::Append:1", rocksdb_kill_odds);
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if (s.ok()) {
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filesize_ += data.size();
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}
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return s;
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}
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Status WritableFileWriter::Close() {
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// Do not quit immediately on failure the file MUST be closed
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Status s;
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// Possible to close it twice now as we MUST close
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// in __dtor, simply flushing is not enough
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// Windows when pre-allocating does not fill with zeros
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// also with unbuffered access we also set the end of data.
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if (!writable_file_) {
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return s;
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}
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s = Flush(); // flush cache to OS
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Status interim;
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// In direct I/O mode we write whole pages so
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// we need to let the file know where data ends.
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if (use_direct_io()) {
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interim = writable_file_->Truncate(filesize_);
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if (!interim.ok() && s.ok()) {
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s = interim;
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}
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}
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TEST_KILL_RANDOM("WritableFileWriter::Close:0", rocksdb_kill_odds);
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interim = writable_file_->Close();
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if (!interim.ok() && s.ok()) {
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s = interim;
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}
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writable_file_.reset();
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TEST_KILL_RANDOM("WritableFileWriter::Close:1", rocksdb_kill_odds);
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return s;
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}
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// write out the cached data to the OS cache or storage if direct I/O
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// enabled
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Status WritableFileWriter::Flush() {
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Status s;
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TEST_KILL_RANDOM("WritableFileWriter::Flush:0",
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rocksdb_kill_odds * REDUCE_ODDS2);
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if (buf_.CurrentSize() > 0) {
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if (use_direct_io()) {
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#ifndef ROCKSDB_LITE
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s = WriteDirect();
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#endif // !ROCKSDB_LITE
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} else {
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s = WriteBuffered(buf_.BufferStart(), buf_.CurrentSize());
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}
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if (!s.ok()) {
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return s;
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}
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}
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s = writable_file_->Flush();
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if (!s.ok()) {
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return s;
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}
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// sync OS cache to disk for every bytes_per_sync_
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// TODO: give log file and sst file different options (log
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// files could be potentially cached in OS for their whole
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// life time, thus we might not want to flush at all).
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// We try to avoid sync to the last 1MB of data. For two reasons:
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// (1) avoid rewrite the same page that is modified later.
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// (2) for older version of OS, write can block while writing out
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// the page.
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// Xfs does neighbor page flushing outside of the specified ranges. We
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// need to make sure sync range is far from the write offset.
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if (!use_direct_io() && bytes_per_sync_) {
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const uint64_t kBytesNotSyncRange = 1024 * 1024; // recent 1MB is not synced.
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const uint64_t kBytesAlignWhenSync = 4 * 1024; // Align 4KB.
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if (filesize_ > kBytesNotSyncRange) {
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uint64_t offset_sync_to = filesize_ - kBytesNotSyncRange;
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offset_sync_to -= offset_sync_to % kBytesAlignWhenSync;
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assert(offset_sync_to >= last_sync_size_);
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if (offset_sync_to > 0 &&
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offset_sync_to - last_sync_size_ >= bytes_per_sync_) {
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s = RangeSync(last_sync_size_, offset_sync_to - last_sync_size_);
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last_sync_size_ = offset_sync_to;
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}
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}
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}
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return s;
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}
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Status WritableFileWriter::Sync(bool use_fsync) {
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Status s = Flush();
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if (!s.ok()) {
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return s;
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}
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TEST_KILL_RANDOM("WritableFileWriter::Sync:0", rocksdb_kill_odds);
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if (!use_direct_io() && pending_sync_) {
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s = SyncInternal(use_fsync);
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if (!s.ok()) {
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return s;
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}
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}
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TEST_KILL_RANDOM("WritableFileWriter::Sync:1", rocksdb_kill_odds);
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pending_sync_ = false;
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return Status::OK();
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}
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Status WritableFileWriter::SyncWithoutFlush(bool use_fsync) {
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if (!writable_file_->IsSyncThreadSafe()) {
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return Status::NotSupported(
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"Can't WritableFileWriter::SyncWithoutFlush() because "
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"WritableFile::IsSyncThreadSafe() is false");
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}
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TEST_SYNC_POINT("WritableFileWriter::SyncWithoutFlush:1");
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Status s = SyncInternal(use_fsync);
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TEST_SYNC_POINT("WritableFileWriter::SyncWithoutFlush:2");
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return s;
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}
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Status WritableFileWriter::SyncInternal(bool use_fsync) {
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Status s;
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IOSTATS_TIMER_GUARD(fsync_nanos);
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TEST_SYNC_POINT("WritableFileWriter::SyncInternal:0");
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if (use_fsync) {
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s = writable_file_->Fsync();
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} else {
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s = writable_file_->Sync();
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}
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return s;
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}
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Status WritableFileWriter::RangeSync(uint64_t offset, uint64_t nbytes) {
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IOSTATS_TIMER_GUARD(range_sync_nanos);
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TEST_SYNC_POINT("WritableFileWriter::RangeSync:0");
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return writable_file_->RangeSync(offset, nbytes);
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}
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size_t WritableFileWriter::RequestToken(size_t bytes, bool align) {
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Env::IOPriority io_priority;
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if (rate_limiter_ && (io_priority = writable_file_->GetIOPriority()) <
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Env::IO_TOTAL) {
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bytes = std::min(
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bytes, static_cast<size_t>(rate_limiter_->GetSingleBurstBytes()));
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if (align) {
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// Here we may actually require more than burst and block
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// but we can not write less than one page at a time on direct I/O
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// thus we may want not to use ratelimiter
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size_t alignment = buf_.Alignment();
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bytes = std::max(alignment, TruncateToPageBoundary(alignment, bytes));
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}
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rate_limiter_->Request(bytes, io_priority, stats_);
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}
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return bytes;
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}
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// This method writes to disk the specified data and makes use of the rate
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// limiter if available
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Status WritableFileWriter::WriteBuffered(const char* data, size_t size) {
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Status s;
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assert(!use_direct_io());
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const char* src = data;
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size_t left = size;
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while (left > 0) {
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size_t allowed = RequestToken(left, false);
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{
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IOSTATS_TIMER_GUARD(write_nanos);
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TEST_SYNC_POINT("WritableFileWriter::Flush:BeforeAppend");
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s = writable_file_->Append(Slice(src, allowed));
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if (!s.ok()) {
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return s;
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}
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}
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IOSTATS_ADD(bytes_written, allowed);
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TEST_KILL_RANDOM("WritableFileWriter::WriteBuffered:0", rocksdb_kill_odds);
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left -= allowed;
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src += allowed;
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}
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buf_.Size(0);
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return s;
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}
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// This flushes the accumulated data in the buffer. We pad data with zeros if
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// necessary to the whole page.
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// However, during automatic flushes padding would not be necessary.
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// We always use RateLimiter if available. We move (Refit) any buffer bytes
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// that are left over the
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// whole number of pages to be written again on the next flush because we can
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// only write on aligned
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// offsets.
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#ifndef ROCKSDB_LITE
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Status WritableFileWriter::WriteDirect() {
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assert(use_direct_io());
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Status s;
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const size_t alignment = buf_.Alignment();
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assert((next_write_offset_ % alignment) == 0);
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// Calculate whole page final file advance if all writes succeed
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size_t file_advance =
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TruncateToPageBoundary(alignment, buf_.CurrentSize());
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// Calculate the leftover tail, we write it here padded with zeros BUT we
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// will write
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// it again in the future either on Close() OR when the current whole page
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// fills out
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size_t leftover_tail = buf_.CurrentSize() - file_advance;
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// Round up and pad
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buf_.PadToAlignmentWith(0);
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const char* src = buf_.BufferStart();
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uint64_t write_offset = next_write_offset_;
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size_t left = buf_.CurrentSize();
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while (left > 0) {
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// Check how much is allowed
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size_t size = RequestToken(left, true);
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{
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IOSTATS_TIMER_GUARD(write_nanos);
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TEST_SYNC_POINT("WritableFileWriter::Flush:BeforeAppend");
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// direct writes must be positional
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s = writable_file_->PositionedAppend(Slice(src, size), write_offset);
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if (!s.ok()) {
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buf_.Size(file_advance + leftover_tail);
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return s;
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}
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}
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IOSTATS_ADD(bytes_written, size);
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left -= size;
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src += size;
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write_offset += size;
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assert((next_write_offset_ % alignment) == 0);
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}
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if (s.ok()) {
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// Move the tail to the beginning of the buffer
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// This never happens during normal Append but rather during
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// explicit call to Flush()/Sync() or Close()
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buf_.RefitTail(file_advance, leftover_tail);
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// This is where we start writing next time which may or not be
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// the actual file size on disk. They match if the buffer size
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// is a multiple of whole pages otherwise filesize_ is leftover_tail
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// behind
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next_write_offset_ += file_advance;
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}
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return s;
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}
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#endif // !ROCKSDB_LITE
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namespace {
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class ReadaheadRandomAccessFile : public RandomAccessFile {
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public:
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ReadaheadRandomAccessFile(std::unique_ptr<RandomAccessFile>&& file,
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size_t readahead_size)
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: file_(std::move(file)),
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alignment_(file_->GetRequiredBufferAlignment()),
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readahead_size_(Roundup(readahead_size, alignment_)),
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forward_calls_(file_->ShouldForwardRawRequest()),
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buffer_(),
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buffer_offset_(0),
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buffer_len_(0) {
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if (!forward_calls_) {
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buffer_.Alignment(alignment_);
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buffer_.AllocateNewBuffer(readahead_size_);
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} else if (readahead_size_ > 0) {
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file_->EnableReadAhead();
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}
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}
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ReadaheadRandomAccessFile(const ReadaheadRandomAccessFile&) = delete;
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ReadaheadRandomAccessFile& operator=(const ReadaheadRandomAccessFile&) = delete;
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virtual Status Read(uint64_t offset, size_t n, Slice* result,
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char* scratch) const override {
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if (n + alignment_ >= readahead_size_) {
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return file_->Read(offset, n, result, scratch);
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}
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// On Windows in unbuffered mode this will lead to double buffering
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// and double locking so we avoid that.
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// In normal mode Windows caches so much data from disk that we do
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// not need readahead.
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if (forward_calls_) {
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return file_->Read(offset, n, result, scratch);
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}
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std::unique_lock<std::mutex> lk(lock_);
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size_t cached_len = 0;
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// Check if there is a cache hit, means that [offset, offset + n) is either
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// complitely or partially in the buffer
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// If it's completely cached, including end of file case when offset + n is
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// greater than EOF, return
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if (TryReadFromCache(offset, n, &cached_len, scratch) &&
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(cached_len == n ||
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// End of file
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buffer_len_ < readahead_size_)) {
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*result = Slice(scratch, cached_len);
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return Status::OK();
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}
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size_t advanced_offset = offset + cached_len;
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// In the case of cache hit advanced_offset is already aligned, means that
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// chunk_offset equals to advanced_offset
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size_t chunk_offset = TruncateToPageBoundary(alignment_, advanced_offset);
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Slice readahead_result;
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Status s = ReadIntoBuffer(chunk_offset, readahead_size_);
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if (s.ok()) {
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// In the case of cache miss, i.e. when cached_len equals 0, an offset can
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// exceed the file end position, so the following check is required
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if (advanced_offset < chunk_offset + buffer_len_) {
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// In the case of cache miss, the first chunk_padding bytes in buffer_
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// are
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// stored for alignment only and must be skipped
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size_t chunk_padding = advanced_offset - chunk_offset;
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auto remaining_len =
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std::min(buffer_len_ - chunk_padding, n - cached_len);
|
|
memcpy(scratch + cached_len, buffer_.BufferStart() + chunk_padding,
|
|
remaining_len);
|
|
*result = Slice(scratch, cached_len + remaining_len);
|
|
} else {
|
|
*result = Slice(scratch, cached_len);
|
|
}
|
|
}
|
|
return s;
|
|
}
|
|
|
|
virtual Status Prefetch(uint64_t offset, size_t n) override {
|
|
size_t prefetch_offset = TruncateToPageBoundary(alignment_, offset);
|
|
if (prefetch_offset == buffer_offset_) {
|
|
return Status::OK();
|
|
}
|
|
return ReadIntoBuffer(prefetch_offset, offset - prefetch_offset + n);
|
|
}
|
|
|
|
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);
|
|
}
|
|
|
|
virtual bool use_direct_io() const override {
|
|
return file_->use_direct_io();
|
|
}
|
|
|
|
private:
|
|
bool TryReadFromCache(uint64_t offset, size_t n, size_t* cached_len,
|
|
char* scratch) const {
|
|
if (offset < buffer_offset_ || offset >= buffer_offset_ + buffer_len_) {
|
|
*cached_len = 0;
|
|
return false;
|
|
}
|
|
uint64_t offset_in_buffer = offset - buffer_offset_;
|
|
*cached_len =
|
|
std::min(buffer_len_ - static_cast<size_t>(offset_in_buffer), n);
|
|
memcpy(scratch, buffer_.BufferStart() + offset_in_buffer, *cached_len);
|
|
return true;
|
|
}
|
|
|
|
Status ReadIntoBuffer(uint64_t offset, size_t n) const {
|
|
if (n > buffer_.Capacity()) {
|
|
n = buffer_.Capacity();
|
|
}
|
|
Slice result;
|
|
Status s = file_->Read(offset, n, &result, buffer_.BufferStart());
|
|
if (s.ok()) {
|
|
buffer_offset_ = offset;
|
|
buffer_len_ = result.size();
|
|
}
|
|
return s;
|
|
}
|
|
|
|
std::unique_ptr<RandomAccessFile> file_;
|
|
const size_t alignment_;
|
|
size_t readahead_size_;
|
|
const bool forward_calls_;
|
|
|
|
mutable std::mutex lock_;
|
|
mutable AlignedBuffer 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<RandomAccessFile> result(
|
|
new ReadaheadRandomAccessFile(std::move(file), readahead_size));
|
|
return result;
|
|
}
|
|
|
|
Status NewWritableFile(Env* env, const std::string& fname,
|
|
unique_ptr<WritableFile>* result,
|
|
const EnvOptions& options) {
|
|
Status s = env->NewWritableFile(fname, result, options);
|
|
TEST_KILL_RANDOM("NewWritableFile:0", rocksdb_kill_odds * REDUCE_ODDS2);
|
|
return s;
|
|
}
|
|
|
|
} // namespace rocksdb
|