rocksdb/file/writable_file_writer.cc

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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root 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 "file/writable_file_writer.h"
#include <algorithm>
#include <mutex>
#include "monitoring/histogram.h"
#include "monitoring/iostats_context_imp.h"
#include "port/port.h"
#include "test_util/sync_point.h"
#include "util/random.h"
#include "util/rate_limiter.h"
namespace rocksdb {
Status WritableFileWriter::Append(const Slice& data) {
const char* src = data.data();
size_t left = data.size();
Status s;
pending_sync_ = true;
TEST_KILL_RANDOM("WritableFileWriter::Append:0",
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);
}
// See whether we need to enlarge the buffer to avoid the flush
if (buf_.Capacity() - buf_.CurrentSize() < left) {
for (size_t cap = buf_.Capacity();
cap < max_buffer_size_; // There is still room to increase
cap *= 2) {
// See whether the next available size is large enough.
// Buffer will never be increased to more than max_buffer_size_.
size_t desired_capacity = std::min(cap * 2, max_buffer_size_);
if (desired_capacity - buf_.CurrentSize() >= left ||
(use_direct_io() && desired_capacity == max_buffer_size_)) {
buf_.AllocateNewBuffer(desired_capacity, true);
break;
}
}
}
// Flush only when buffered I/O
if (!use_direct_io() && (buf_.Capacity() - buf_.CurrentSize()) < left) {
if (buf_.CurrentSize() > 0) {
s = Flush();
if (!s.ok()) {
return s;
}
}
assert(buf_.CurrentSize() == 0);
}
// We never write directly to disk with direct I/O on.
// or we simply use it for its original purpose to accumulate many small
// chunks
if (use_direct_io() || (buf_.Capacity() >= left)) {
while (left > 0) {
size_t appended = buf_.Append(src, left);
left -= appended;
src += appended;
if (left > 0) {
s = Flush();
if (!s.ok()) {
break;
}
}
}
} else {
// Writing directly to file bypassing the buffer
assert(buf_.CurrentSize() == 0);
s = WriteBuffered(src, left);
}
TEST_KILL_RANDOM("WritableFileWriter::Append:1", rocksdb_kill_odds);
if (s.ok()) {
filesize_ += data.size();
}
return s;
}
Status WritableFileWriter::Pad(const size_t pad_bytes) {
assert(pad_bytes < kDefaultPageSize);
size_t left = pad_bytes;
size_t cap = buf_.Capacity() - buf_.CurrentSize();
// Assume pad_bytes is small compared to buf_ capacity. So we always
// use buf_ rather than write directly to file in certain cases like
// Append() does.
while (left) {
size_t append_bytes = std::min(cap, left);
buf_.PadWith(append_bytes, 0);
left -= append_bytes;
if (left > 0) {
Status s = Flush();
if (!s.ok()) {
return s;
}
}
cap = buf_.Capacity() - buf_.CurrentSize();
}
pending_sync_ = true;
filesize_ += pad_bytes;
return Status::OK();
}
Status WritableFileWriter::Close() {
// Do not quit immediately on failure the file MUST be closed
Status s;
// Possible to close it twice now as we MUST close
// in __dtor, simply flushing is not enough
// Windows when pre-allocating does not fill with zeros
// also with unbuffered access we also set the end of data.
if (!writable_file_) {
return s;
}
s = Flush(); // flush cache to OS
Status interim;
// In direct I/O mode we write whole pages so
// we need to let the file know where data ends.
if (use_direct_io()) {
interim = writable_file_->Truncate(filesize_);
if (interim.ok()) {
interim = writable_file_->Fsync();
}
if (!interim.ok() && s.ok()) {
s = interim;
}
}
TEST_KILL_RANDOM("WritableFileWriter::Close:0", rocksdb_kill_odds);
interim = writable_file_->Close();
if (!interim.ok() && s.ok()) {
s = interim;
}
writable_file_.reset();
TEST_KILL_RANDOM("WritableFileWriter::Close:1", rocksdb_kill_odds);
return s;
}
// write out the cached data to the OS cache or storage if direct I/O
// enabled
Status WritableFileWriter::Flush() {
Status s;
TEST_KILL_RANDOM("WritableFileWriter::Flush:0",
rocksdb_kill_odds * REDUCE_ODDS2);
if (buf_.CurrentSize() > 0) {
if (use_direct_io()) {
#ifndef ROCKSDB_LITE
if (pending_sync_) {
s = WriteDirect();
}
#endif // !ROCKSDB_LITE
} else {
s = WriteBuffered(buf_.BufferStart(), buf_.CurrentSize());
}
if (!s.ok()) {
return s;
}
}
s = writable_file_->Flush();
if (!s.ok()) {
return s;
}
// 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 (!use_direct_io() && bytes_per_sync_) {
const uint64_t kBytesNotSyncRange =
1024 * 1024; // recent 1MB is not synced.
const 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_) {
s = RangeSync(last_sync_size_, offset_sync_to - last_sync_size_);
last_sync_size_ = offset_sync_to;
}
}
}
return s;
}
Status WritableFileWriter::Sync(bool use_fsync) {
Status s = Flush();
if (!s.ok()) {
return s;
}
TEST_KILL_RANDOM("WritableFileWriter::Sync:0", rocksdb_kill_odds);
if (!use_direct_io() && pending_sync_) {
s = SyncInternal(use_fsync);
if (!s.ok()) {
return s;
}
}
TEST_KILL_RANDOM("WritableFileWriter::Sync:1", rocksdb_kill_odds);
pending_sync_ = 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");
auto prev_perf_level = GetPerfLevel();
IOSTATS_CPU_TIMER_GUARD(cpu_write_nanos, env_);
if (use_fsync) {
s = writable_file_->Fsync();
} else {
s = writable_file_->Sync();
}
SetPerfLevel(prev_perf_level);
return s;
}
Status WritableFileWriter::RangeSync(uint64_t offset, uint64_t nbytes) {
IOSTATS_TIMER_GUARD(range_sync_nanos);
TEST_SYNC_POINT("WritableFileWriter::RangeSync:0");
return writable_file_->RangeSync(offset, nbytes);
}
// This method writes to disk the specified data and makes use of the rate
// limiter if available
Status WritableFileWriter::WriteBuffered(const char* data, size_t size) {
Status s;
assert(!use_direct_io());
const char* src = data;
size_t left = size;
while (left > 0) {
size_t allowed;
if (rate_limiter_ != nullptr) {
allowed = rate_limiter_->RequestToken(
left, 0 /* alignment */, writable_file_->GetIOPriority(), stats_,
RateLimiter::OpType::kWrite);
} else {
allowed = left;
}
{
IOSTATS_TIMER_GUARD(write_nanos);
TEST_SYNC_POINT("WritableFileWriter::Flush:BeforeAppend");
#ifndef ROCKSDB_LITE
FileOperationInfo::TimePoint start_ts;
uint64_t old_size = writable_file_->GetFileSize();
if (ShouldNotifyListeners()) {
start_ts = std::chrono::system_clock::now();
old_size = next_write_offset_;
}
#endif
{
auto prev_perf_level = GetPerfLevel();
IOSTATS_CPU_TIMER_GUARD(cpu_write_nanos, env_);
s = writable_file_->Append(Slice(src, allowed));
SetPerfLevel(prev_perf_level);
}
#ifndef ROCKSDB_LITE
if (ShouldNotifyListeners()) {
auto finish_ts = std::chrono::system_clock::now();
NotifyOnFileWriteFinish(old_size, allowed, start_ts, finish_ts, s);
}
#endif
if (!s.ok()) {
return s;
}
}
IOSTATS_ADD(bytes_written, allowed);
TEST_KILL_RANDOM("WritableFileWriter::WriteBuffered:0", rocksdb_kill_odds);
left -= allowed;
src += allowed;
}
buf_.Size(0);
return s;
}
// This flushes the accumulated data in the buffer. We pad data with zeros if
// necessary to the whole page.
// However, during automatic flushes padding would not be necessary.
// We always use RateLimiter if available. We move (Refit) any buffer bytes
// that are left over the
// whole number of pages to be written again on the next flush because we can
// only write on aligned
// offsets.
#ifndef ROCKSDB_LITE
Status WritableFileWriter::WriteDirect() {
assert(use_direct_io());
Status s;
const size_t alignment = buf_.Alignment();
assert((next_write_offset_ % alignment) == 0);
// Calculate whole page final file advance if all writes succeed
size_t file_advance = TruncateToPageBoundary(alignment, buf_.CurrentSize());
// Calculate the leftover tail, we write it here padded with zeros BUT we
// will write
// it again in the future either on Close() OR when the current whole page
// fills out
size_t leftover_tail = buf_.CurrentSize() - file_advance;
// Round up and pad
buf_.PadToAlignmentWith(0);
const char* src = buf_.BufferStart();
uint64_t write_offset = next_write_offset_;
size_t left = buf_.CurrentSize();
while (left > 0) {
// Check how much is allowed
size_t size;
if (rate_limiter_ != nullptr) {
size = rate_limiter_->RequestToken(left, buf_.Alignment(),
writable_file_->GetIOPriority(),
stats_, RateLimiter::OpType::kWrite);
} else {
size = left;
}
{
IOSTATS_TIMER_GUARD(write_nanos);
TEST_SYNC_POINT("WritableFileWriter::Flush:BeforeAppend");
FileOperationInfo::TimePoint start_ts;
if (ShouldNotifyListeners()) {
start_ts = std::chrono::system_clock::now();
}
// direct writes must be positional
s = writable_file_->PositionedAppend(Slice(src, size), write_offset);
if (ShouldNotifyListeners()) {
auto finish_ts = std::chrono::system_clock::now();
NotifyOnFileWriteFinish(write_offset, size, start_ts, finish_ts, s);
}
if (!s.ok()) {
buf_.Size(file_advance + leftover_tail);
return s;
}
}
IOSTATS_ADD(bytes_written, size);
left -= size;
src += size;
write_offset += size;
assert((next_write_offset_ % alignment) == 0);
}
if (s.ok()) {
// Move the tail to the beginning of the buffer
// This never happens during normal Append but rather during
// explicit call to Flush()/Sync() or Close()
buf_.RefitTail(file_advance, leftover_tail);
// This is where we start writing next time which may or not be
// the actual file size on disk. They match if the buffer size
// is a multiple of whole pages otherwise filesize_ is leftover_tail
// behind
next_write_offset_ += file_advance;
}
return s;
}
#endif // !ROCKSDB_LITE
} // namespace rocksdb