rocksdb/file/prefetch_test.cc
Akanksha Mahajan cd79a00903 Make BlockBasedTable::kMaxAutoReadAheadSize configurable (#7951)
Summary:
RocksDB does auto-readahead for iterators on noticing more
than two reads for a table file. The readahead starts at 8KB and doubles on every
additional read upto BlockBasedTable::kMaxAutoReadAheadSize which is
256*1024.
This PR adds a new option BlockBasedTableOptions::max_auto_readahead_size which
replaces BlockBasedTable::kMaxAutoReadAheadSize and the new option can be
configured.
If max_auto_readahead_size is set 0 then no implicit auto prefetching will
be done. If max_auto_readahead_size provided is less than
8KB (which is initial readahead size used by rocksdb in case of
auto-readahead), readahead size will remain same as max_auto_readahead_size.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7951

Test Plan: Add new unit test case.

Reviewed By: anand1976

Differential Revision: D26568085

Pulled By: akankshamahajan15

fbshipit-source-id: b6543520fc74e97d859f2002328d4c5254d417af
2021-02-23 16:54:08 -08:00

334 lines
11 KiB
C++

// 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 "db/db_test_util.h"
#include "test_util/sync_point.h"
namespace ROCKSDB_NAMESPACE {
class MockFS;
class MockRandomAccessFile : public FSRandomAccessFileWrapper {
public:
MockRandomAccessFile(std::unique_ptr<FSRandomAccessFile>& file,
bool support_prefetch, std::atomic_int& prefetch_count)
: FSRandomAccessFileWrapper(file.get()),
file_(std::move(file)),
support_prefetch_(support_prefetch),
prefetch_count_(prefetch_count) {}
IOStatus Prefetch(uint64_t offset, size_t n, const IOOptions& options,
IODebugContext* dbg) override {
if (support_prefetch_) {
prefetch_count_.fetch_add(1);
return target()->Prefetch(offset, n, options, dbg);
} else {
return IOStatus::NotSupported("Prefetch not supported");
}
}
private:
std::unique_ptr<FSRandomAccessFile> file_;
const bool support_prefetch_;
std::atomic_int& prefetch_count_;
};
class MockFS : public FileSystemWrapper {
public:
explicit MockFS(const std::shared_ptr<FileSystem>& wrapped,
bool support_prefetch)
: FileSystemWrapper(wrapped), support_prefetch_(support_prefetch) {}
IOStatus NewRandomAccessFile(const std::string& fname,
const FileOptions& opts,
std::unique_ptr<FSRandomAccessFile>* result,
IODebugContext* dbg) override {
std::unique_ptr<FSRandomAccessFile> file;
IOStatus s;
s = target()->NewRandomAccessFile(fname, opts, &file, dbg);
result->reset(
new MockRandomAccessFile(file, support_prefetch_, prefetch_count_));
return s;
}
void ClearPrefetchCount() { prefetch_count_ = 0; }
bool IsPrefetchCalled() { return prefetch_count_ > 0; }
private:
const bool support_prefetch_;
std::atomic_int prefetch_count_{0};
};
class PrefetchTest
: public DBTestBase,
public ::testing::WithParamInterface<std::tuple<bool, bool>> {
public:
PrefetchTest() : DBTestBase("/prefetch_test", true) {}
};
std::string BuildKey(int num, std::string postfix = "") {
return "my_key_" + std::to_string(num) + postfix;
}
TEST_P(PrefetchTest, Basic) {
// First param is if the mockFS support_prefetch or not
bool support_prefetch =
std::get<0>(GetParam()) &&
test::IsPrefetchSupported(env_->GetFileSystem(), dbname_);
// Second param is if directIO is enabled or not
bool use_direct_io = std::get<1>(GetParam());
const int kNumKeys = 1100;
std::shared_ptr<MockFS> fs =
std::make_shared<MockFS>(env_->GetFileSystem(), support_prefetch);
std::unique_ptr<Env> env(new CompositeEnvWrapper(env_, fs));
Options options = CurrentOptions();
options.write_buffer_size = 1024;
options.create_if_missing = true;
options.compression = kNoCompression;
options.env = env.get();
if (use_direct_io) {
options.use_direct_reads = true;
options.use_direct_io_for_flush_and_compaction = true;
}
int buff_prefetch_count = 0;
SyncPoint::GetInstance()->SetCallBack("FilePrefetchBuffer::Prefetch:Start",
[&](void*) { buff_prefetch_count++; });
SyncPoint::GetInstance()->EnableProcessing();
Status s = TryReopen(options);
if (use_direct_io && (s.IsNotSupported() || s.IsInvalidArgument())) {
// If direct IO is not supported, skip the test
return;
} else {
ASSERT_OK(s);
}
// create first key range
WriteBatch batch;
for (int i = 0; i < kNumKeys; i++) {
ASSERT_OK(batch.Put(BuildKey(i), "value for range 1 key"));
}
ASSERT_OK(db_->Write(WriteOptions(), &batch));
// create second key range
batch.Clear();
for (int i = 0; i < kNumKeys; i++) {
ASSERT_OK(batch.Put(BuildKey(i, "key2"), "value for range 2 key"));
}
ASSERT_OK(db_->Write(WriteOptions(), &batch));
// delete second key range
batch.Clear();
for (int i = 0; i < kNumKeys; i++) {
ASSERT_OK(batch.Delete(BuildKey(i, "key2")));
}
ASSERT_OK(db_->Write(WriteOptions(), &batch));
// compact database
std::string start_key = BuildKey(0);
std::string end_key = BuildKey(kNumKeys - 1);
Slice least(start_key.data(), start_key.size());
Slice greatest(end_key.data(), end_key.size());
// commenting out the line below causes the example to work correctly
ASSERT_OK(db_->CompactRange(CompactRangeOptions(), &least, &greatest));
if (support_prefetch && !use_direct_io) {
// If underline file system supports prefetch, and directIO is not enabled
// make sure prefetch() is called and FilePrefetchBuffer is not used.
ASSERT_TRUE(fs->IsPrefetchCalled());
fs->ClearPrefetchCount();
ASSERT_EQ(0, buff_prefetch_count);
} else {
// If underline file system doesn't support prefetch, or directIO is
// enabled, make sure prefetch() is not called and FilePrefetchBuffer is
// used.
ASSERT_FALSE(fs->IsPrefetchCalled());
ASSERT_GT(buff_prefetch_count, 0);
buff_prefetch_count = 0;
}
// count the keys
{
auto iter = std::unique_ptr<Iterator>(db_->NewIterator(ReadOptions()));
int num_keys = 0;
for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
num_keys++;
}
}
// Make sure prefetch is called only if file system support prefetch.
if (support_prefetch && !use_direct_io) {
ASSERT_TRUE(fs->IsPrefetchCalled());
fs->ClearPrefetchCount();
ASSERT_EQ(0, buff_prefetch_count);
} else {
ASSERT_FALSE(fs->IsPrefetchCalled());
ASSERT_GT(buff_prefetch_count, 0);
buff_prefetch_count = 0;
}
Close();
}
#ifndef ROCKSDB_LITE
TEST_P(PrefetchTest, ConfigureAutoMaxReadaheadSize) {
// First param is if the mockFS support_prefetch or not
bool support_prefetch =
std::get<0>(GetParam()) &&
test::IsPrefetchSupported(env_->GetFileSystem(), dbname_);
// Second param is if directIO is enabled or not
bool use_direct_io = std::get<1>(GetParam());
std::shared_ptr<MockFS> fs =
std::make_shared<MockFS>(env_->GetFileSystem(), support_prefetch);
std::unique_ptr<Env> env(new CompositeEnvWrapper(env_, fs));
Options options = CurrentOptions();
options.write_buffer_size = 1024;
options.create_if_missing = true;
options.compression = kNoCompression;
options.env = env.get();
options.disable_auto_compactions = true;
if (use_direct_io) {
options.use_direct_reads = true;
options.use_direct_io_for_flush_and_compaction = true;
}
BlockBasedTableOptions table_options;
table_options.no_block_cache = true;
table_options.cache_index_and_filter_blocks = false;
table_options.metadata_block_size = 1024;
table_options.index_type =
BlockBasedTableOptions::IndexType::kTwoLevelIndexSearch;
table_options.max_auto_readahead_size = 0;
options.table_factory.reset(NewBlockBasedTableFactory(table_options));
int buff_prefetch_count = 0;
SyncPoint::GetInstance()->SetCallBack("FilePrefetchBuffer::Prefetch:Start",
[&](void*) { buff_prefetch_count++; });
// DB open will create table readers unless we reduce the table cache
// capacity. SanitizeOptions will set max_open_files to minimum of 20. Table
// cache is allocated with max_open_files - 10 as capacity. So override
// max_open_files to 10 so table cache capacity will become 0. This will
// prevent file open during DB open and force the file to be opened during
// Iteration.
SyncPoint::GetInstance()->SetCallBack(
"SanitizeOptions::AfterChangeMaxOpenFiles", [&](void* arg) {
int* max_open_files = (int*)arg;
*max_open_files = 11;
});
SyncPoint::GetInstance()->EnableProcessing();
Status s = TryReopen(options);
if (use_direct_io && (s.IsNotSupported() || s.IsInvalidArgument())) {
// If direct IO is not supported, skip the test
return;
} else {
ASSERT_OK(s);
}
Random rnd(309);
int key_count = 0;
const int num_keys_per_level = 100;
// Level 0 : Keys in range [0, 99], Level 1:[100, 199], Level 2:[200, 299].
for (int level = 2; level >= 0; level--) {
key_count = level * num_keys_per_level;
for (int i = 0; i < num_keys_per_level; ++i) {
ASSERT_OK(Put(Key(key_count++), rnd.RandomString(500)));
}
ASSERT_OK(Flush());
MoveFilesToLevel(level);
}
Close();
std::vector<int> buff_prefectch_level_count = {0, 0, 0};
TryReopen(options);
{
auto iter = std::unique_ptr<Iterator>(db_->NewIterator(ReadOptions()));
fs->ClearPrefetchCount();
buff_prefetch_count = 0;
for (int level = 2; level >= 0; level--) {
key_count = level * num_keys_per_level;
switch (level) {
case 0:
// max_auto_readahead_size is set 0 so data and index blocks are not
// prefetched.
ASSERT_OK(db_->SetOptions(
{{"block_based_table_factory", "{max_auto_readahead_size=0;}"}}));
break;
case 1:
// max_auto_readahead_size is set less than
// BlockBasedTable::kInitAutoReadaheadSize. So readahead_size remains
// equal to max_auto_readahead_size.
ASSERT_OK(db_->SetOptions({{"block_based_table_factory",
"{max_auto_readahead_size=4096;}"}}));
break;
case 2:
ASSERT_OK(db_->SetOptions({{"block_based_table_factory",
"{max_auto_readahead_size=65536;}"}}));
break;
default:
assert(false);
}
for (int i = 0; i < num_keys_per_level; ++i) {
iter->Seek(Key(key_count++));
iter->Next();
}
buff_prefectch_level_count[level] = buff_prefetch_count;
if (support_prefetch && !use_direct_io) {
if (level == 0) {
ASSERT_FALSE(fs->IsPrefetchCalled());
} else {
ASSERT_TRUE(fs->IsPrefetchCalled());
}
fs->ClearPrefetchCount();
} else {
ASSERT_FALSE(fs->IsPrefetchCalled());
if (level == 0) {
ASSERT_EQ(buff_prefetch_count, 0);
} else {
ASSERT_GT(buff_prefetch_count, 0);
}
buff_prefetch_count = 0;
}
}
}
if (!support_prefetch) {
ASSERT_GT(buff_prefectch_level_count[1], buff_prefectch_level_count[2]);
}
SyncPoint::GetInstance()->DisableProcessing();
SyncPoint::GetInstance()->ClearAllCallBacks();
Close();
}
INSTANTIATE_TEST_CASE_P(PrefetchTest, PrefetchTest,
::testing::Combine(::testing::Bool(),
::testing::Bool()));
#endif // !ROCKSDB_LITE
class PrefetchTest1 : public DBTestBase,
public ::testing::WithParamInterface<bool> {
public:
PrefetchTest1() : DBTestBase("/prefetch_test1", true) {}
};
} // namespace ROCKSDB_NAMESPACE
int main(int argc, char** argv) {
::testing::InitGoogleTest(&argc, argv);
return RUN_ALL_TESTS();
}