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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/random_access_file_reader.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_NAMESPACE {
Status RandomAccessFileReader::Read(uint64_t offset, size_t n, Slice* result,
char* scratch, bool for_compaction) const {
Status s;
uint64_t elapsed = 0;
{
StopWatch sw(env_, stats_, hist_type_,
(stats_ != nullptr) ? &elapsed : nullptr, true /*overwrite*/,
true /*delay_enabled*/);
auto prev_perf_level = GetPerfLevel();
IOSTATS_TIMER_GUARD(read_nanos);
if (use_direct_io()) {
#ifndef ROCKSDB_LITE
size_t alignment = file_->GetRequiredBufferAlignment();
size_t aligned_offset =
TruncateToPageBoundary(alignment, static_cast<size_t>(offset));
size_t offset_advance = static_cast<size_t>(offset) - aligned_offset;
size_t read_size =
Roundup(static_cast<size_t>(offset + n), alignment) - aligned_offset;
AlignedBuffer buf;
buf.Alignment(alignment);
buf.AllocateNewBuffer(read_size);
while (buf.CurrentSize() < read_size) {
size_t allowed;
if (for_compaction && rate_limiter_ != nullptr) {
allowed = rate_limiter_->RequestToken(
buf.Capacity() - buf.CurrentSize(), buf.Alignment(),
Env::IOPriority::IO_LOW, stats_, RateLimiter::OpType::kRead);
} else {
assert(buf.CurrentSize() == 0);
allowed = read_size;
}
Slice tmp;
FileOperationInfo::TimePoint start_ts;
uint64_t orig_offset = 0;
if (ShouldNotifyListeners()) {
start_ts = std::chrono::system_clock::now();
orig_offset = aligned_offset + buf.CurrentSize();
}
{
IOSTATS_CPU_TIMER_GUARD(cpu_read_nanos, env_);
s = file_->Read(aligned_offset + buf.CurrentSize(), allowed,
IOOptions(), &tmp, buf.Destination(), nullptr);
}
if (ShouldNotifyListeners()) {
auto finish_ts = std::chrono::system_clock::now();
NotifyOnFileReadFinish(orig_offset, tmp.size(), start_ts, finish_ts,
s);
}
buf.Size(buf.CurrentSize() + tmp.size());
if (!s.ok() || tmp.size() < allowed) {
break;
}
}
size_t res_len = 0;
if (s.ok() && offset_advance < buf.CurrentSize()) {
res_len = buf.Read(scratch, offset_advance,
std::min(buf.CurrentSize() - offset_advance, n));
}
*result = Slice(scratch, res_len);
#endif // !ROCKSDB_LITE
} else {
size_t pos = 0;
const char* res_scratch = nullptr;
while (pos < n) {
size_t allowed;
if (for_compaction && rate_limiter_ != nullptr) {
if (rate_limiter_->IsRateLimited(RateLimiter::OpType::kRead)) {
sw.DelayStart();
}
allowed = rate_limiter_->RequestToken(n - pos, 0 /* alignment */,
Env::IOPriority::IO_LOW, stats_,
RateLimiter::OpType::kRead);
if (rate_limiter_->IsRateLimited(RateLimiter::OpType::kRead)) {
sw.DelayStop();
}
} else {
allowed = n;
}
Slice tmp_result;
#ifndef ROCKSDB_LITE
FileOperationInfo::TimePoint start_ts;
if (ShouldNotifyListeners()) {
start_ts = std::chrono::system_clock::now();
}
#endif
{
IOSTATS_CPU_TIMER_GUARD(cpu_read_nanos, env_);
s = file_->Read(offset + pos, allowed, IOOptions(), &tmp_result,
scratch + pos, nullptr);
}
#ifndef ROCKSDB_LITE
if (ShouldNotifyListeners()) {
auto finish_ts = std::chrono::system_clock::now();
NotifyOnFileReadFinish(offset + pos, tmp_result.size(), start_ts,
finish_ts, s);
}
#endif
if (res_scratch == nullptr) {
// we can't simply use `scratch` because reads of mmap'd files return
// data in a different buffer.
res_scratch = tmp_result.data();
} else {
// make sure chunks are inserted contiguously into `res_scratch`.
assert(tmp_result.data() == res_scratch + pos);
}
pos += tmp_result.size();
if (!s.ok() || tmp_result.size() < allowed) {
break;
}
}
*result = Slice(res_scratch, s.ok() ? pos : 0);
}
IOSTATS_ADD_IF_POSITIVE(bytes_read, result->size());
SetPerfLevel(prev_perf_level);
}
if (stats_ != nullptr && file_read_hist_ != nullptr) {
file_read_hist_->Add(elapsed);
}
return s;
}
Status RandomAccessFileReader::MultiRead(FSReadRequest* read_reqs,
size_t num_reqs) const {
Status s;
uint64_t elapsed = 0;
assert(!use_direct_io());
{
StopWatch sw(env_, stats_, hist_type_,
(stats_ != nullptr) ? &elapsed : nullptr, true /*overwrite*/,
true /*delay_enabled*/);
auto prev_perf_level = GetPerfLevel();
IOSTATS_TIMER_GUARD(read_nanos);
#ifndef ROCKSDB_LITE
FileOperationInfo::TimePoint start_ts;
if (ShouldNotifyListeners()) {
start_ts = std::chrono::system_clock::now();
}
#endif // ROCKSDB_LITE
{
IOSTATS_CPU_TIMER_GUARD(cpu_read_nanos, env_);
s = file_->MultiRead(read_reqs, num_reqs, IOOptions(), nullptr);
}
for (size_t i = 0; i < num_reqs; ++i) {
#ifndef ROCKSDB_LITE
if (ShouldNotifyListeners()) {
auto finish_ts = std::chrono::system_clock::now();
NotifyOnFileReadFinish(read_reqs[i].offset, read_reqs[i].result.size(),
start_ts, finish_ts, read_reqs[i].status);
}
#endif // ROCKSDB_LITE
IOSTATS_ADD_IF_POSITIVE(bytes_read, read_reqs[i].result.size());
}
SetPerfLevel(prev_perf_level);
}
if (stats_ != nullptr && file_read_hist_ != nullptr) {
file_read_hist_->Add(elapsed);
}
return s;
}
} // namespace ROCKSDB_NAMESPACE
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