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Support direct IO in RandomAccessFileReader::MultiRead (#6446) 

Summary:
By supporting direct IO in RandomAccessFileReader::MultiRead, the benefits of parallel IO (IO uring) and direct IO can be combined.

In direct IO mode, read requests are aligned and merged together before being issued to RandomAccessFile::MultiRead, so blocks in the original requests might share the same underlying buffer, the shared buffers are returned in `aligned_bufs`, which is a new parameter of the `MultiRead` API.

For example, suppose alignment requirement for direct IO is 4KB, one request is (offset: 1KB, len: 1KB), another request is (offset: 3KB, len: 1KB), then since they all belong to page (offset: 0, len: 4KB), `MultiRead` only reads the page with direct IO into a buffer on heap, and returns 2 Slices referencing regions in that same buffer. See `random_access_file_reader_test.cc` for more examples.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6446

Test Plan: Added a new test `random_access_file_reader_test.cc`.

Reviewed By: anand1976

Differential Revision: D20097518

Pulled By: cheng-chang

fbshipit-source-id: ca48a8faf9c3af146465c102ef6b266a363e78d1
This commit is contained in:
Cheng Chang 2020-03-20 16:15:40 -07:00 committed by Facebook GitHub Bot
parent 5fd152b7ad
commit 4fc216649d
11 changed files with 402 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
CMakeLists.txt
View File

@ -1022,6 +1022,7 @@ if(WITH_TESTS)
env/io_posix_test.cc
env/mock_env_test.cc
file/delete_scheduler_test.cc
file/random_access_file_reader_test.cc
logging/auto_roll_logger_test.cc
logging/env_logger_test.cc
logging/event_logger_test.cc

4
Makefile
View File

@ -513,6 +513,7 @@ TESTS = \
fault_injection_test \
filelock_test \
filename_test \
random_access_file_reader_test \
file_reader_writer_test \
block_based_filter_block_test \
full_filter_block_test \
@ -1505,6 +1506,9 @@ delete_scheduler_test: file/delete_scheduler_test.o $(LIBOBJECTS) $(TESTHARNESS)
filename_test: db/filename_test.o $(LIBOBJECTS) $(TESTHARNESS)
$(AM_LINK)
random_access_file_reader_test: file/random_access_file_reader_test.o $(LIBOBJECTS) $(TESTHARNESS) $(TESTUTIL)
$(AM_LINK)
file_reader_writer_test: util/file_reader_writer_test.o $(LIBOBJECTS) $(TESTHARNESS)
$(AM_LINK)

7
TARGETS
View File

@ -1300,6 +1300,13 @@ ROCKS_TESTS = [
[],
[],
],
[
"random_access_file_reader_test",
"file/random_access_file_reader_test.cc",
"serial",
[],
[],
],
[
"random_test",
"util/random_test.cc",

111
file/random_access_file_reader.cc
View File

@ -20,11 +20,11 @@
#include "util/rate_limiter.h"
namespace ROCKSDB_NAMESPACE {
Status RandomAccessFileReader::Read(uint64_t offset, size_t n, Slice* result,
char* scratch,
std::unique_ptr<const char[]>* internal_buf,
char* scratch, AlignedBuf* aligned_buf,
bool for_compaction) const {
(void) internal_buf;
(void)aligned_buf;
Status s;
uint64_t elapsed = 0;
{
@ -81,11 +81,11 @@ Status RandomAccessFileReader::Read(uint64_t offset, size_t n, Slice* result,
size_t res_len = 0;
if (s.ok() && offset_advance < buf.CurrentSize()) {
res_len = std::min(buf.CurrentSize() - offset_advance, n);
if (internal_buf == nullptr) {
if (aligned_buf == nullptr) {
buf.Read(scratch, offset_advance, res_len);
} else {
scratch = buf.BufferStart();
internal_buf->reset(buf.Release());
aligned_buf->reset(buf.Release());
}
}
*result = Slice(scratch, res_len);
@ -154,11 +154,44 @@ Status RandomAccessFileReader::Read(uint64_t offset, size_t n, Slice* result,
return s;
}
size_t End(const FSReadRequest& r) {
return static_cast<size_t>(r.offset) + r.len;
}
FSReadRequest Align(const FSReadRequest& r, size_t alignment) {
FSReadRequest req;
req.offset = static_cast<uint64_t>(
TruncateToPageBoundary(alignment, static_cast<size_t>(r.offset)));
req.len = Roundup(End(r), alignment) - req.offset;
return req;
}
// Try to merge src to dest if they have overlap.
//
// Each request represents an inclusive interval [offset, offset + len].
// If the intervals have overlap, update offset and len to represent the
// merged interval, and return true.
// Otherwise, do nothing and return false.
bool TryMerge(FSReadRequest* dest, const FSReadRequest& src) {
size_t dest_offset = static_cast<size_t>(dest->offset);
size_t src_offset = static_cast<size_t>(src.offset);
size_t dest_end = End(*dest);
size_t src_end = End(src);
if (std::max(dest_offset, dest_offset) > std::min(dest_end, src_end)) {
return false;
}
dest->offset = static_cast<uint64_t>(std::min(dest_offset, src_offset));
dest->len = std::max(dest_end, src_end) - dest->offset;
return true;
}
Status RandomAccessFileReader::MultiRead(FSReadRequest* read_reqs,
size_t num_reqs) const {
size_t num_reqs,
AlignedBuf* aligned_buf) const {
(void)aligned_buf; // suppress warning of unused variable in LITE mode
assert(num_reqs > 0);
Status s;
uint64_t elapsed = 0;
assert(!use_direct_io());
{
StopWatch sw(env_, stats_, hist_type_,
(stats_ != nullptr) ? &elapsed : nullptr, true /*overwrite*/,
@ -166,6 +199,44 @@ Status RandomAccessFileReader::MultiRead(FSReadRequest* read_reqs,
auto prev_perf_level = GetPerfLevel();
IOSTATS_TIMER_GUARD(read_nanos);
FSReadRequest* fs_reqs = read_reqs;
size_t num_fs_reqs = num_reqs;
#ifndef ROCKSDB_LITE
std::vector<FSReadRequest> aligned_reqs;
if (use_direct_io()) {
// num_reqs is the max possible size,
// this can reduce std::vecector's internal resize operations.
aligned_reqs.reserve(num_reqs);
// Align and merge the read requests.
size_t alignment = file_->GetRequiredBufferAlignment();
aligned_reqs.push_back(Align(read_reqs[0], alignment));
for (size_t i = 1; i < num_reqs; i++) {
const auto& r = Align(read_reqs[i], alignment);
if (!TryMerge(&aligned_reqs.back(), r)) {
aligned_reqs.push_back(r);
}
}
// Allocate aligned buffer and let scratch buffers point to it.
size_t total_len = 0;
for (const auto& r : aligned_reqs) {
total_len += r.len;
}
AlignedBuffer buf;
buf.Alignment(alignment);
buf.AllocateNewBuffer(total_len);
char* scratch = buf.BufferStart();
for (auto& r : aligned_reqs) {
r.scratch = scratch;
scratch += r.len;
}
aligned_buf->reset(buf.Release());
fs_reqs = aligned_reqs.data();
num_fs_reqs = aligned_reqs.size();
}
#endif // ROCKSDB_LITE
#ifndef ROCKSDB_LITE
FileOperationInfo::TimePoint start_ts;
if (ShouldNotifyListeners()) {
@ -174,8 +245,31 @@ Status RandomAccessFileReader::MultiRead(FSReadRequest* read_reqs,
#endif // ROCKSDB_LITE
{
IOSTATS_CPU_TIMER_GUARD(cpu_read_nanos, env_);
s = file_->MultiRead(read_reqs, num_reqs, IOOptions(), nullptr);
s = file_->MultiRead(fs_reqs, num_fs_reqs, IOOptions(), nullptr);
}
#ifndef ROCKSDB_LITE
if (use_direct_io()) {
// Populate results in the unaligned read requests.
size_t aligned_i = 0;
for (size_t i = 0; i < num_reqs; i++) {
auto& r = read_reqs[i];
if (static_cast<size_t>(r.offset) > End(aligned_reqs[aligned_i])) {
aligned_i++;
}
const auto& fs_r = fs_reqs[aligned_i];
r.status = fs_r.status;
if (r.status.ok()) {
uint64_t offset = r.offset - fs_r.offset;
size_t len = std::min(r.len, static_cast<size_t>(fs_r.len - offset));
r.result = Slice(fs_r.scratch + offset, len);
} else {
r.result = Slice();
}
}
}
#endif // ROCKSDB_LITE
for (size_t i = 0; i < num_reqs; ++i) {
#ifndef ROCKSDB_LITE
if (ShouldNotifyListeners()) {
@ -194,4 +288,5 @@ Status RandomAccessFileReader::MultiRead(FSReadRequest* read_reqs,
return s;
}
} // namespace ROCKSDB_NAMESPACE

23
file/random_access_file_reader.h
View File

@ -22,6 +22,8 @@ namespace ROCKSDB_NAMESPACE {
class Statistics;
class HistogramImpl;
using AlignedBuf = std::unique_ptr<const char[]>;
// RandomAccessFileReader is a wrapper on top of Env::RnadomAccessFile. It is
// responsible for:
// - Handling Buffered and Direct reads appropriately.
@ -59,7 +61,7 @@ class RandomAccessFileReader {
public:
explicit RandomAccessFileReader(
std::unique_ptr<FSRandomAccessFile>&& raf, std::string _file_name,
std::unique_ptr<FSRandomAccessFile>&& raf, const std::string& _file_name,
Env* env = nullptr, Statistics* stats = nullptr, uint32_t hist_type = 0,
HistogramImpl* file_read_hist = nullptr,
RateLimiter* rate_limiter = nullptr,
@ -106,17 +108,22 @@ class RandomAccessFileReader {
// 1. if using mmap, result is stored in a buffer other than scratch;
// 2. if not using mmap, result is stored in the buffer starting from scratch.
//
// In direct IO mode, an internal aligned buffer is allocated.
// 1. If internal_buf is null, then results are copied to the buffer
// In direct IO mode, an aligned buffer is allocated internally.
// 1. If aligned_buf is null, then results are copied to the buffer
// starting from scratch;
// 2. Otherwise, scratch is not used and can be null, the internal_buf owns
// 2. Otherwise, scratch is not used and can be null, the aligned_buf owns
// the internally allocated buffer on return, and the result refers to a
// region in internal_buf.
// region in aligned_buf.
Status Read(uint64_t offset, size_t n, Slice* result, char* scratch,
std::unique_ptr<const char[]>* internal_buf,
bool for_compaction = false) const;
AlignedBuf* aligned_buf, bool for_compaction = false) const;
Status MultiRead(FSReadRequest* reqs, size_t num_reqs) const;
// REQUIRES:
// num_reqs > 0, reqs do not overlap, and offsets in reqs are increasing.
// In non-direct IO mode, aligned_buf should be null;
// In direct IO mode, aligned_buf stores the aligned buffer allocated inside
// MultiRead, the result Slices in reqs refer to aligned_buf.
Status MultiRead(FSReadRequest* reqs, size_t num_reqs,
AlignedBuf* aligned_buf) const;
Status Prefetch(uint64_t offset, size_t n) const {
return file_->Prefetch(offset, n, IOOptions(), nullptr);

255
file/random_access_file_reader_test.cc Normal file
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@ -0,0 +1,255 @@
// 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).
#include "port/port.h"
#include "port/stack_trace.h"
#include "rocksdb/file_system.h"
#include "file/random_access_file_reader.h"
#include "test_util/testharness.h"
#include "test_util/testutil.h"
namespace ROCKSDB_NAMESPACE {
class RandomAccessFileReaderTest : public testing::Test {
public:
void SetUp() override {
#ifdef OS_LINUX
// TEST_TMPDIR may be set to /dev/shm in Makefile,
// but /dev/shm does not support direct IO.
// The default TEST_TMPDIR is under /tmp, but /tmp might also be a tmpfs
// which does not support direct IO neither.
unsetenv("TEST_TMPDIR");
char* tmpdir = getenv("DISK_TEMP_DIR");
if (tmpdir == nullptr) {
tmpdir = getenv("HOME");
}
if (tmpdir != nullptr) {
setenv("TEST_TMPDIR", tmpdir, 1);
}
#endif
env_ = Env::Default();
fs_ = FileSystem::Default();
test_dir_ = test::PerThreadDBPath("random_access_file_reader_test");
ASSERT_OK(fs_->CreateDir(test_dir_, IOOptions(), nullptr));
alignment_ = GetAlignment();
}
void TearDown() override {
EXPECT_OK(test::DestroyDir(env_, test_dir_));
}
bool IsDirectIOSupported() {
Write(".direct", "");
FileOptions opt;
opt.use_direct_reads = true;
std::unique_ptr<FSRandomAccessFile> f;
auto s = fs_->NewRandomAccessFile(Path(".direct"), opt, &f, nullptr);
return s.ok();
}
void Write(const std::string& fname, const std::string& content) {
std::unique_ptr<FSWritableFile> f;
ASSERT_OK(fs_->NewWritableFile(Path(fname), FileOptions(), &f, nullptr));
ASSERT_OK(f->Append(content, IOOptions(), nullptr));
ASSERT_OK(f->Close(IOOptions(), nullptr));
}
void Read(const std::string& fname, const FileOptions& opts,
std::unique_ptr<RandomAccessFileReader>* reader) {
std::string fpath = Path(fname);
std::unique_ptr<FSRandomAccessFile> f;
ASSERT_OK(fs_->NewRandomAccessFile(fpath, opts, &f, nullptr));
(*reader).reset(new RandomAccessFileReader(std::move(f), fpath, env_));
}
void AssertResult(const std::string& content,
const std::vector<FSReadRequest>& reqs) {
for (const auto& r : reqs) {
ASSERT_OK(r.status);
ASSERT_EQ(r.len, r.result.size());
ASSERT_EQ(content.substr(r.offset, r.len), r.result.ToString());
}
}
size_t alignment() const { return alignment_; }
private:
Env* env_;
std::shared_ptr<FileSystem> fs_;
std::string test_dir_;
size_t alignment_;
std::string Path(const std::string& fname) {
return test_dir_ + "/" + fname;
}
size_t GetAlignment() {
std::string f = "get_alignment";
Write(f, "");
std::unique_ptr<RandomAccessFileReader> r;
Read(f, FileOptions(), &r);
size_t alignment = r->file()->GetRequiredBufferAlignment();
EXPECT_OK(fs_->DeleteFile(Path(f), IOOptions(), nullptr));
return alignment;
}
};
TEST_F(RandomAccessFileReaderTest, MultiReadDirectIO) {
if (!IsDirectIOSupported()) {
printf("Direct IO is not supported, skip this test\n");
return;
}
// Creates a file with 3 pages.
std::string fname = "multi-read-direct-io";
Random rand(0);
std::string content;
test::RandomString(&rand, 3 * static_cast<int>(alignment()), &content);
Write(fname, content);
FileOptions opts;
opts.use_direct_reads = true;
std::unique_ptr<RandomAccessFileReader> r;
Read(fname, opts, &r);
ASSERT_TRUE(r->use_direct_io());
{
// Reads 2 blocks in the 1st page.
// The results should be SharedSlices of the same underlying buffer.
//
// Illustration (each x is a 1/4 page)
// First page: xxxx
// 1st block: x
// 2nd block: xx
FSReadRequest r0;
r0.offset = 0;
r0.len = alignment() / 4;
r0.scratch = nullptr;
FSReadRequest r1;
r1.offset = alignment() / 2;
r1.len = alignment() / 2;
r1.scratch = nullptr;
std::vector<FSReadRequest> reqs;
reqs.push_back(std::move(r0));
reqs.push_back(std::move(r1));
AlignedBuf aligned_buf;
ASSERT_OK(r->MultiRead(reqs.data(), reqs.size(), &aligned_buf));
AssertResult(content, reqs);
}
{
// Reads 3 blocks:
// 1st block in the 1st page;
// 2nd block from the middle of the 1st page to the middle of the 2nd page;
// 3rd block in the 2nd page.
// The results should be SharedSlices of the same underlying buffer.
//
// Illustration (each x is a 1/4 page)
// 2 pages: xxxxxxxx
// 1st block: x
// 2nd block: xxxx
// 3rd block: x
FSReadRequest r0;
r0.offset = 0;
r0.len = alignment() / 4;
r0.scratch = nullptr;
FSReadRequest r1;
r1.offset = alignment() / 2;
r1.len = alignment();
r1.scratch = nullptr;
FSReadRequest r2;
r2.offset = 2 * alignment() - alignment() / 4;
r2.len = alignment() / 4;
r2.scratch = nullptr;
std::vector<FSReadRequest> reqs;
reqs.push_back(std::move(r0));
reqs.push_back(std::move(r1));
reqs.push_back(std::move(r2));
AlignedBuf aligned_buf;
ASSERT_OK(r->MultiRead(reqs.data(), reqs.size(), &aligned_buf));
AssertResult(content, reqs);
}
{
// Reads 3 blocks:
// 1st block in the middle of the 1st page;
// 2nd block in the middle of the 2nd page;
// 3rd block in the middle of the 3rd page.
// The results should be SharedSlices of the same underlying buffer.
//
// Illustration (each x is a 1/4 page)
// 3 pages: xxxxxxxxxxxx
// 1st block: xx
// 2nd block: xx
// 3rd block: xx
FSReadRequest r0;
r0.offset = alignment() / 4;
r0.len = alignment() / 2;
r0.scratch = nullptr;
FSReadRequest r1;
r1.offset = alignment() + alignment() / 4;
r1.len = alignment() / 2;
r1.scratch = nullptr;
FSReadRequest r2;
r2.offset = 2 * alignment() + alignment() / 4;
r2.len = alignment() / 2;
r2.scratch = nullptr;
std::vector<FSReadRequest> reqs;
reqs.push_back(std::move(r0));
reqs.push_back(std::move(r1));
reqs.push_back(std::move(r2));
AlignedBuf aligned_buf;
ASSERT_OK(r->MultiRead(reqs.data(), reqs.size(), &aligned_buf));
AssertResult(content, reqs);
}
{
// Reads 2 blocks:
// 1st block in the middle of the 1st page;
// 2nd block in the middle of the 3rd page.
// The results are two different buffers.
//
// Illustration (each x is a 1/4 page)
// 3 pages: xxxxxxxxxxxx
// 1st block: xx
// 2nd block: xx
FSReadRequest r0;
r0.offset = alignment() / 4;
r0.len = alignment() / 2;
r0.scratch = nullptr;
FSReadRequest r1;
r1.offset = 2 * alignment() + alignment() / 4;
r1.len = alignment() / 2;
r1.scratch = nullptr;
std::vector<FSReadRequest> reqs;
reqs.push_back(std::move(r0));
reqs.push_back(std::move(r1));
AlignedBuf aligned_buf;
ASSERT_OK(r->MultiRead(reqs.data(), reqs.size(), &aligned_buf));
AssertResult(content, reqs);
}
}
} // namespace ROCKSDB_NAMESPACE
int main(int argc, char** argv) {
ROCKSDB_NAMESPACE::port::InstallStackTraceHandler();
::testing::InitGoogleTest(&argc, argv);
return RUN_ALL_TESTS();
}

2
port/win/env_win.cc
View File

@ -1424,7 +1424,7 @@ Status WinEnv::UnlockFile(FileLock* lock) {
return winenv_io_.UnlockFile(lock);
}
Status WinEnv::GetTestDirectory(std::string* result) {
Status WinEnv::GetTestDirectory(std::string* result) {
return winenv_io_.GetTestDirectory(result);
}

1
src.mk
View File

@ -395,6 +395,7 @@ MAIN_SOURCES = \
env/env_test.cc \
env/io_posix_test.cc \
env/mock_env_test.cc \
file/random_access_file_reader_test.cc \
logging/auto_roll_logger_test.cc \
logging/env_logger_test.cc \
logging/event_logger_test.cc \

6
table/block_based/block_based_table_reader.cc
View File

@ -1607,7 +1607,6 @@ void BlockBasedTable::RetrieveMultipleBlocks(
req.scratch = scratch + buf_offset;
buf_offset += req.len;
}
req.status = IOStatus::OK();
read_reqs.emplace_back(req);
}
@ -1628,11 +1627,10 @@ void BlockBasedTable::RetrieveMultipleBlocks(
} else {
req.scratch = scratch + buf_offset;
}
req.status = IOStatus::OK();
read_reqs.emplace_back(req);
}
file->MultiRead(&read_reqs[0], read_reqs.size());
file->MultiRead(&read_reqs[0], read_reqs.size(), nullptr);
idx_in_batch = 0;
size_t valid_batch_idx = 0;
@ -1699,7 +1697,7 @@ void BlockBasedTable::RetrieveMultipleBlocks(
// in each read request. Checksum is stored in the block trailer,
// which is handle.size() + 1.
s = ROCKSDB_NAMESPACE::VerifyChecksum(footer.checksum(),
req.result.data() + req_offset,
data + req_offset,
handle.size() + 1, expected);
TEST_SYNC_POINT_CALLBACK("RetrieveMultipleBlocks:VerifyChecksum", &s);
}

6
utilities/blob_db/blob_db_impl.cc
View File

@ -1483,7 +1483,7 @@ Status BlobDBImpl::GetRawBlobFromFile(const Slice& key, uint64_t file_number,
// Allocate the buffer. This is safe in C++11
std::string buf;
std::unique_ptr<const char[]> internal_buf;
AlignedBuf aligned_buf;
// A partial blob record contain checksum, key and value.
Slice blob_record;
@ -1492,11 +1492,11 @@ Status BlobDBImpl::GetRawBlobFromFile(const Slice& key, uint64_t file_number,
StopWatch read_sw(env_, statistics_, BLOB_DB_BLOB_FILE_READ_MICROS);
if (reader->use_direct_io()) {
s = reader->Read(record_offset, static_cast<size_t>(record_size),
&blob_record, nullptr, &internal_buf);
&blob_record, nullptr, &aligned_buf);
} else {
buf.reserve(static_cast<size_t>(record_size));
s = reader->Read(record_offset, static_cast<size_t>(record_size),
&blob_record, &buf[0], nullptr);
&blob_record, &buf[0], nullptr);
}
RecordTick(statistics_, BLOB_DB_BLOB_FILE_BYTES_READ, blob_record.size());
}

18
utilities/blob_db/blob_file.cc
View File

@ -139,11 +139,11 @@ Status BlobFile::ReadFooter(BlobLogFooter* bf) {
Slice result;
std::string buf;
std::unique_ptr<const char[]> internal_buf;
AlignedBuf aligned_buf;
Status s;
if (ra_file_reader_->use_direct_io()) {
s = ra_file_reader_->Read(footer_offset, BlobLogFooter::kSize, &result,
nullptr, &internal_buf);
nullptr, &aligned_buf);
} else {
buf.reserve(BlobLogFooter::kSize + 10);
s = ra_file_reader_->Read(footer_offset, BlobLogFooter::kSize, &result,
@ -263,11 +263,11 @@ Status BlobFile::ReadMetadata(Env* env, const EnvOptions& env_options) {
// Read file header.
std::string header_buf;
std::unique_ptr<const char[]> internal_buf;
AlignedBuf aligned_buf;
Slice header_slice;
if (file_reader->use_direct_io()) {
s = file_reader->Read(0, BlobLogHeader::kSize, &header_slice, nullptr,
&internal_buf);
&aligned_buf);
} else {
header_buf.reserve(BlobLogHeader::kSize);
s = file_reader->Read(0, BlobLogHeader::kSize, &header_slice,
@ -306,12 +306,14 @@ Status BlobFile::ReadMetadata(Env* env, const EnvOptions& env_options) {
std::string footer_buf;
Slice footer_slice;
if (file_reader->use_direct_io()) {
s = file_reader->Read(file_size - BlobLogFooter::kSize, BlobLogFooter::kSize,
&footer_slice, nullptr, &internal_buf);
s = file_reader->Read(file_size - BlobLogFooter::kSize,
BlobLogFooter::kSize, &footer_slice, nullptr,
&aligned_buf);
} else {
footer_buf.reserve(BlobLogFooter::kSize);
s = file_reader->Read(file_size - BlobLogFooter::kSize, BlobLogFooter::kSize,
&footer_slice, &footer_buf[0], nullptr);
s = file_reader->Read(file_size - BlobLogFooter::kSize,
BlobLogFooter::kSize, &footer_slice, &footer_buf[0],
nullptr);
}
if (!s.ok()) {
ROCKS_LOG_ERROR(info_log_,