rocksdb/table/block_fetcher_test.cc
Cheng Chang 40497a875a Reduce memory copies when fetching and uncompressing blocks from SST files (#6689)
Summary:
In https://github.com/facebook/rocksdb/pull/6455, we modified the interface of `RandomAccessFileReader::Read` to be able to get rid of memcpy in direct IO mode.
This PR applies the new interface to `BlockFetcher` when reading blocks from SST files in direct IO mode.

Without this PR, in direct IO mode, when fetching and uncompressing compressed blocks, `BlockFetcher` will first copy the raw compressed block into `BlockFetcher::compressed_buf_` or `BlockFetcher::stack_buf_` inside `RandomAccessFileReader::Read` depending on the block size. then during uncompressing, it will copy the uncompressed block into `BlockFetcher::heap_buf_`.

In this PR, we get rid of the first memcpy and directly uncompress the block from `direct_io_buf_` to `heap_buf_`.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6689

Test Plan: A new unit test `block_fetcher_test` is added.

Reviewed By: anand1976

Differential Revision: D21006729

Pulled By: cheng-chang

fbshipit-source-id: 2370b92c24075692423b81277415feb2aed5d980
2020-04-24 15:32:56 -07:00

476 lines
18 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 "table/block_fetcher.h"
#include "db/table_properties_collector.h"
#include "options/options_helper.h"
#include "port/port.h"
#include "port/stack_trace.h"
#include "table/block_based/binary_search_index_reader.h"
#include "table/block_based/block_based_table_builder.h"
#include "table/block_based/block_based_table_factory.h"
#include "table/block_based/block_based_table_reader.h"
#include "table/format.h"
#include "test_util/testharness.h"
#include "test_util/testutil.h"
namespace ROCKSDB_NAMESPACE {
namespace {
class CountedMemoryAllocator : public MemoryAllocator {
public:
const char* Name() const override { return "CountedMemoryAllocator"; }
void* Allocate(size_t size) override {
num_allocations_++;
return static_cast<void*>(new char[size]);
}
void Deallocate(void* p) override {
num_deallocations_++;
delete[] static_cast<char*>(p);
}
int GetNumAllocations() const { return num_allocations_; }
int GetNumDeallocations() const { return num_deallocations_; }
private:
int num_allocations_ = 0;
int num_deallocations_ = 0;
};
struct MemcpyStats {
int num_stack_buf_memcpy = 0;
int num_heap_buf_memcpy = 0;
int num_compressed_buf_memcpy = 0;
};
struct BufAllocationStats {
int num_heap_buf_allocations = 0;
int num_compressed_buf_allocations = 0;
};
struct TestStats {
MemcpyStats memcpy_stats;
BufAllocationStats buf_allocation_stats;
};
class BlockFetcherTest : public testing::Test {
protected:
void SetUp() override {
test::ResetTmpDirForDirectIO();
test_dir_ = test::PerThreadDBPath("block_fetcher_test");
env_ = Env::Default();
fs_ = FileSystem::Default();
ASSERT_OK(fs_->CreateDir(test_dir_, IOOptions(), nullptr));
is_direct_io_supported_ = DetectDirectIOSupport();
}
void TearDown() override { EXPECT_OK(test::DestroyDir(env_, test_dir_)); }
bool IsDirectIOSupported() const { return is_direct_io_supported_; }
void AssertSameBlock(const BlockContents& block1,
const BlockContents& block2) {
ASSERT_EQ(block1.data.ToString(), block2.data.ToString());
}
// Creates a table with kv pairs (i, i) where i ranges from 0 to 9, inclusive.
void CreateTable(const std::string& table_name,
const CompressionType& compression_type) {
std::unique_ptr<WritableFileWriter> writer;
NewFileWriter(table_name, &writer);
// Create table builder.
Options options;
ImmutableCFOptions ioptions(options);
InternalKeyComparator comparator(options.comparator);
ColumnFamilyOptions cf_options;
MutableCFOptions moptions(cf_options);
std::vector<std::unique_ptr<IntTblPropCollectorFactory>> factories;
std::unique_ptr<TableBuilder> table_builder(table_factory_.NewTableBuilder(
TableBuilderOptions(ioptions, moptions, comparator, &factories,
compression_type, 0 /* sample_for_compression */,
CompressionOptions(), false /* skip_filters */,
kDefaultColumnFamilyName, -1 /* level */),
0 /* column_family_id */, writer.get()));
// Build table.
for (int i = 0; i < 9; i++) {
std::string key = ToInternalKey(std::to_string(i));
std::string value = std::to_string(i);
table_builder->Add(key, value);
}
ASSERT_OK(table_builder->Finish());
}
void FetchIndexBlock(const std::string& table_name, bool use_direct_io,
CountedMemoryAllocator* heap_buf_allocator,
CountedMemoryAllocator* compressed_buf_allocator,
MemcpyStats* memcpy_stats, BlockContents* index_block) {
FileOptions fopt;
fopt.use_direct_reads = use_direct_io;
std::unique_ptr<RandomAccessFileReader> file;
NewFileReader(table_name, fopt, &file);
// Get handle of the index block.
Footer footer;
ReadFooter(file.get(), &footer);
const BlockHandle& index_handle = footer.index_handle();
CompressionType compression_type;
FetchBlock(file.get(), index_handle, BlockType::kIndex,
false /* compressed */, false /* do_uncompress */,
heap_buf_allocator, compressed_buf_allocator, index_block,
memcpy_stats, &compression_type);
ASSERT_EQ(compression_type, CompressionType::kNoCompression);
}
// Fetches the first data block in both direct IO and non-direct IO mode.
//
// compressed: whether the data blocks are compressed;
// do_uncompress: whether the data blocks should be uncompressed on fetching.
// compression_type: the expected compression type.
//
// Expects:
// Block contents are the same.
// Bufferr allocation and memory copy statistics are expected.
void TestFetchDataBlock(const std::string& table_name_prefix, bool compressed,
bool do_uncompress,
const TestStats& expected_non_direct_io_stats,
const TestStats& expected_direct_io_stats) {
if (!IsDirectIOSupported()) {
printf("Skip this test since direct IO is not supported\n");
return;
}
for (CompressionType compression_type : GetSupportedCompressions()) {
bool do_compress = compression_type != kNoCompression;
if (compressed != do_compress) continue;
std::string compression_type_str =
CompressionTypeToString(compression_type);
std::string table_name = table_name_prefix + compression_type_str;
CreateTable(table_name, compression_type);
CompressionType expected_compression_type_after_fetch =
(compressed && !do_uncompress) ? compression_type : kNoCompression;
BlockContents blocks[2];
MemcpyStats memcpy_stats[2];
CountedMemoryAllocator heap_buf_allocators[2];
CountedMemoryAllocator compressed_buf_allocators[2];
for (bool use_direct_io : {false, true}) {
FetchFirstDataBlock(
table_name, use_direct_io, compressed, do_uncompress,
expected_compression_type_after_fetch,
&heap_buf_allocators[use_direct_io],
&compressed_buf_allocators[use_direct_io], &blocks[use_direct_io],
&memcpy_stats[use_direct_io]);
}
AssertSameBlock(blocks[0], blocks[1]);
// Check memcpy and buffer allocation statistics.
for (bool use_direct_io : {false, true}) {
const TestStats& expected_stats = use_direct_io
? expected_direct_io_stats
: expected_non_direct_io_stats;
ASSERT_EQ(memcpy_stats[use_direct_io].num_stack_buf_memcpy,
expected_stats.memcpy_stats.num_stack_buf_memcpy);
ASSERT_EQ(memcpy_stats[use_direct_io].num_heap_buf_memcpy,
expected_stats.memcpy_stats.num_heap_buf_memcpy);
ASSERT_EQ(memcpy_stats[use_direct_io].num_compressed_buf_memcpy,
expected_stats.memcpy_stats.num_compressed_buf_memcpy);
ASSERT_EQ(heap_buf_allocators[use_direct_io].GetNumAllocations(),
expected_stats.buf_allocation_stats.num_heap_buf_allocations);
ASSERT_EQ(
compressed_buf_allocators[use_direct_io].GetNumAllocations(),
expected_stats.buf_allocation_stats.num_compressed_buf_allocations);
// The allocated buffers are not deallocated until
// the block content is deleted.
ASSERT_EQ(heap_buf_allocators[use_direct_io].GetNumDeallocations(), 0);
ASSERT_EQ(
compressed_buf_allocators[use_direct_io].GetNumDeallocations(), 0);
blocks[use_direct_io].allocation.reset();
ASSERT_EQ(heap_buf_allocators[use_direct_io].GetNumDeallocations(),
expected_stats.buf_allocation_stats.num_heap_buf_allocations);
ASSERT_EQ(
compressed_buf_allocators[use_direct_io].GetNumDeallocations(),
expected_stats.buf_allocation_stats.num_compressed_buf_allocations);
}
}
}
private:
std::string test_dir_;
Env* env_;
std::shared_ptr<FileSystem> fs_;
BlockBasedTableFactory table_factory_;
bool is_direct_io_supported_;
std::string Path(const std::string& fname) { return test_dir_ + "/" + fname; }
void WriteToFile(const std::string& content, const std::string& filename) {
std::unique_ptr<FSWritableFile> f;
ASSERT_OK(fs_->NewWritableFile(Path(filename), FileOptions(), &f, nullptr));
ASSERT_OK(f->Append(content, IOOptions(), nullptr));
ASSERT_OK(f->Close(IOOptions(), nullptr));
}
bool DetectDirectIOSupport() {
WriteToFile("", ".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 NewFileWriter(const std::string& filename,
std::unique_ptr<WritableFileWriter>* writer) {
std::string path = Path(filename);
EnvOptions env_options;
std::unique_ptr<WritableFile> file;
ASSERT_OK(env_->NewWritableFile(path, &file, env_options));
writer->reset(new WritableFileWriter(
NewLegacyWritableFileWrapper(std::move(file)), path, env_options));
}
void NewFileReader(const std::string& filename, const FileOptions& opt,
std::unique_ptr<RandomAccessFileReader>* reader) {
std::string path = Path(filename);
std::unique_ptr<FSRandomAccessFile> f;
ASSERT_OK(fs_->NewRandomAccessFile(path, opt, &f, nullptr));
reader->reset(new RandomAccessFileReader(std::move(f), path, env_));
}
void NewTableReader(const ImmutableCFOptions& ioptions,
const FileOptions& foptions,
const InternalKeyComparator& comparator,
const std::string& table_name,
std::unique_ptr<BlockBasedTable>* table) {
std::unique_ptr<RandomAccessFileReader> file;
NewFileReader(table_name, foptions, &file);
uint64_t file_size = 0;
ASSERT_OK(env_->GetFileSize(Path(table_name), &file_size));
std::unique_ptr<TableReader> table_reader;
ASSERT_OK(BlockBasedTable::Open(ioptions, EnvOptions(),
table_factory_.table_options(), comparator,
std::move(file), file_size, &table_reader));
table->reset(reinterpret_cast<BlockBasedTable*>(table_reader.release()));
}
std::string ToInternalKey(const std::string& key) {
InternalKey internal_key(key, 0, ValueType::kTypeValue);
return internal_key.Encode().ToString();
}
void ReadFooter(RandomAccessFileReader* file, Footer* footer) {
uint64_t file_size = 0;
ASSERT_OK(env_->GetFileSize(file->file_name(), &file_size));
ReadFooterFromFile(file, nullptr /* prefetch_buffer */, file_size, footer,
kBlockBasedTableMagicNumber);
}
// NOTE: compression_type returns the compression type of the fetched block
// contents, so if the block is fetched and uncompressed, then it's
// kNoCompression.
void FetchBlock(RandomAccessFileReader* file, const BlockHandle& block,
BlockType block_type, bool compressed, bool do_uncompress,
MemoryAllocator* heap_buf_allocator,
MemoryAllocator* compressed_buf_allocator,
BlockContents* contents, MemcpyStats* stats,
CompressionType* compresstion_type) {
Options options;
ImmutableCFOptions ioptions(options);
ReadOptions roptions;
PersistentCacheOptions persistent_cache_options;
Footer footer;
ReadFooter(file, &footer);
std::unique_ptr<BlockFetcher> fetcher(new BlockFetcher(
file, nullptr /* prefetch_buffer */, footer, roptions, block, contents,
ioptions, do_uncompress, compressed, block_type,
UncompressionDict::GetEmptyDict(), persistent_cache_options,
heap_buf_allocator, compressed_buf_allocator));
ASSERT_OK(fetcher->ReadBlockContents());
stats->num_stack_buf_memcpy = fetcher->TEST_GetNumStackBufMemcpy();
stats->num_heap_buf_memcpy = fetcher->TEST_GetNumHeapBufMemcpy();
stats->num_compressed_buf_memcpy =
fetcher->TEST_GetNumCompressedBufMemcpy();
*compresstion_type = fetcher->get_compression_type();
}
// NOTE: expected_compression_type is the expected compression
// type of the fetched block content, if the block is uncompressed,
// then the expected compression type is kNoCompression.
void FetchFirstDataBlock(const std::string& table_name, bool use_direct_io,
bool compressed, bool do_uncompress,
CompressionType expected_compression_type,
MemoryAllocator* heap_buf_allocator,
MemoryAllocator* compressed_buf_allocator,
BlockContents* block, MemcpyStats* memcpy_stats) {
if (use_direct_io && !IsDirectIOSupported()) {
printf("Skip this test since direct IO is not supported\n");
return;
}
Options options;
ImmutableCFOptions ioptions(options);
InternalKeyComparator comparator(options.comparator);
FileOptions foptions;
foptions.use_direct_reads = use_direct_io;
// Get block handle for the first data block.
std::unique_ptr<BlockBasedTable> table;
NewTableReader(ioptions, foptions, comparator, table_name, &table);
std::unique_ptr<BlockBasedTable::IndexReader> index_reader;
ASSERT_OK(BinarySearchIndexReader::Create(
table.get(), nullptr /* prefetch_buffer */, false /* use_cache */,
false /* prefetch */, false /* pin */, nullptr /* lookup_context */,
&index_reader));
std::unique_ptr<InternalIteratorBase<IndexValue>> iter(
index_reader->NewIterator(
ReadOptions(), false /* disable_prefix_seek */, nullptr /* iter */,
nullptr /* get_context */, nullptr /* lookup_context */));
ASSERT_OK(iter->status());
iter->SeekToFirst();
BlockHandle first_block_handle = iter->value().handle;
// Fetch first data block.
std::unique_ptr<RandomAccessFileReader> file;
NewFileReader(table_name, foptions, &file);
CompressionType compression_type;
FetchBlock(file.get(), first_block_handle, BlockType::kData, compressed,
do_uncompress, heap_buf_allocator, compressed_buf_allocator,
block, memcpy_stats, &compression_type);
ASSERT_EQ(compression_type, expected_compression_type);
}
};
// Fetch index block under both direct IO and non-direct IO.
// Expects:
// the index block contents are the same for both read modes.
TEST_F(BlockFetcherTest, FetchIndexBlock) {
if (!IsDirectIOSupported()) {
printf("Skip this test since direct IO is not supported\n");
return;
}
for (CompressionType compression : GetSupportedCompressions()) {
std::string table_name =
"FetchIndexBlock" + CompressionTypeToString(compression);
CreateTable(table_name, compression);
CountedMemoryAllocator allocator;
MemcpyStats memcpy_stats;
BlockContents indexes[2];
for (bool use_direct_io : {false, true}) {
FetchIndexBlock(table_name, use_direct_io, &allocator, &allocator,
&memcpy_stats, &indexes[use_direct_io]);
}
AssertSameBlock(indexes[0], indexes[1]);
}
}
// Data blocks are not compressed,
// fetch data block under both direct IO and non-direct IO.
// Expects:
// 1. in non-direct IO mode, allocate a heap buffer and memcpy the block
// into the buffer;
// 2. in direct IO mode, allocate a heap buffer and memcpy from the
// direct IO buffer to the heap buffer.
TEST_F(BlockFetcherTest, FetchUncompressedDataBlock) {
MemcpyStats memcpy_stats;
memcpy_stats.num_heap_buf_memcpy = 1;
BufAllocationStats buf_allocation_stats;
buf_allocation_stats.num_heap_buf_allocations = 1;
TestStats expected_stats{memcpy_stats, buf_allocation_stats};
TestFetchDataBlock("FetchUncompressedDataBlock", false, false, expected_stats,
expected_stats);
}
// Data blocks are compressed,
// fetch data block under both direct IO and non-direct IO,
// but do not uncompress.
// Expects:
// 1. in non-direct IO mode, allocate a compressed buffer and memcpy the block
// into the buffer;
// 2. in direct IO mode, allocate a compressed buffer and memcpy from the
// direct IO buffer to the compressed buffer.
TEST_F(BlockFetcherTest, FetchCompressedDataBlock) {
MemcpyStats memcpy_stats;
memcpy_stats.num_compressed_buf_memcpy = 1;
BufAllocationStats buf_allocation_stats;
buf_allocation_stats.num_compressed_buf_allocations = 1;
TestStats expected_stats{memcpy_stats, buf_allocation_stats};
TestFetchDataBlock("FetchCompressedDataBlock", true, false, expected_stats,
expected_stats);
}
// Data blocks are compressed,
// fetch and uncompress data block under both direct IO and non-direct IO.
// Expects:
// 1. in non-direct IO mode, since the block is small, so it's first memcpyed
// to the stack buffer, then a heap buffer is allocated and the block is
// uncompressed into the heap.
// 2. in direct IO mode mode, allocate a heap buffer, then directly uncompress
// and memcpy from the direct IO buffer to the heap buffer.
TEST_F(BlockFetcherTest, FetchAndUncompressCompressedDataBlock) {
TestStats expected_non_direct_io_stats;
{
MemcpyStats memcpy_stats;
memcpy_stats.num_stack_buf_memcpy = 1;
memcpy_stats.num_heap_buf_memcpy = 1;
BufAllocationStats buf_allocation_stats;
buf_allocation_stats.num_heap_buf_allocations = 1;
buf_allocation_stats.num_compressed_buf_allocations = 0;
expected_non_direct_io_stats = {memcpy_stats, buf_allocation_stats};
}
TestStats expected_direct_io_stats;
{
MemcpyStats memcpy_stats;
memcpy_stats.num_heap_buf_memcpy = 1;
BufAllocationStats buf_allocation_stats;
buf_allocation_stats.num_heap_buf_allocations = 1;
expected_direct_io_stats = {memcpy_stats, buf_allocation_stats};
}
TestFetchDataBlock("FetchAndUncompressCompressedDataBlock", true, true,
expected_non_direct_io_stats, expected_direct_io_stats);
}
} // namespace
} // namespace ROCKSDB_NAMESPACE
int main(int argc, char** argv) {
ROCKSDB_NAMESPACE::port::InstallStackTraceHandler();
::testing::InitGoogleTest(&argc, argv);
return RUN_ALL_TESTS();
}