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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 "table/block_fetcher.h"
#include <cassert>
#include <cinttypes>
#include <string>
#include "logging/logging.h"
#include "memory/memory_allocator_impl.h"
#include "monitoring/perf_context_imp.h"
#include "rocksdb/compression_type.h"
#include "rocksdb/env.h"
#include "table/block_based/block.h"
#include "table/block_based/block_based_table_reader.h"
#include "table/block_based/block_type.h"
#include "table/block_based/reader_common.h"
#include "table/format.h"
#include "table/persistent_cache_helper.h"
#include "util/compression.h"
#include "util/stop_watch.h"
namespace ROCKSDB_NAMESPACE {
inline void BlockFetcher::ProcessTrailerIfPresent() {
if (footer_.GetBlockTrailerSize() > 0) {
assert(footer_.GetBlockTrailerSize() == BlockBasedTable::kBlockTrailerSize);
if (read_options_.verify_checksums) {
io_status_ = status_to_io_status(
VerifyBlockChecksum(footer_, slice_.data(), block_size_,
file_->file_name(), handle_.offset()));
RecordTick(ioptions_.stats, BLOCK_CHECKSUM_COMPUTE_COUNT);
if (!io_status_.ok()) {
assert(io_status_.IsCorruption());
RecordTick(ioptions_.stats, BLOCK_CHECKSUM_MISMATCH_COUNT);
}
}
compression_type_ =
BlockBasedTable::GetBlockCompressionType(slice_.data(), block_size_);
} else {
// E.g. plain table or cuckoo table
compression_type_ = kNoCompression;
}
}
inline bool BlockFetcher::TryGetUncompressBlockFromPersistentCache() {
if (cache_options_.persistent_cache &&
!cache_options_.persistent_cache->IsCompressed()) {
Status status = PersistentCacheHelper::LookupUncompressed(
cache_options_, handle_, contents_);
if (status.ok()) {
// uncompressed page is found for the block handle
return true;
} else {
// uncompressed page is not found
if (ioptions_.logger && !status.IsNotFound()) {
assert(!status.ok());
ROCKS_LOG_INFO(ioptions_.logger,
"Error reading from persistent cache. %s",
status.ToString().c_str());
}
}
}
return false;
}
inline bool BlockFetcher::TryGetFromPrefetchBuffer() {
if (prefetch_buffer_ != nullptr) {
IOOptions opts;
IOStatus io_s = file_->PrepareIOOptions(read_options_, opts);
if (io_s.ok()) {
bool read_from_prefetch_buffer = false;
if (read_options_.async_io && !for_compaction_) {
read_from_prefetch_buffer = prefetch_buffer_->TryReadFromCacheAsync(
opts, file_, handle_.offset(), block_size_with_trailer_, &slice_,
&io_s, read_options_.rate_limiter_priority);
} else {
read_from_prefetch_buffer = prefetch_buffer_->TryReadFromCache(
opts, file_, handle_.offset(), block_size_with_trailer_, &slice_,
&io_s, read_options_.rate_limiter_priority, for_compaction_);
}
if (read_from_prefetch_buffer) {
ProcessTrailerIfPresent();
if (!io_status_.ok()) {
return true;
}
got_from_prefetch_buffer_ = true;
used_buf_ = const_cast<char*>(slice_.data());
}
}
if (!io_s.ok()) {
io_status_ = io_s;
return true;
}
}
return got_from_prefetch_buffer_;
}
inline bool BlockFetcher::TryGetSerializedBlockFromPersistentCache() {
if (cache_options_.persistent_cache &&
cache_options_.persistent_cache->IsCompressed()) {
std::unique_ptr<char[]> buf;
io_status_ = status_to_io_status(PersistentCacheHelper::LookupSerialized(
cache_options_, handle_, &buf, block_size_with_trailer_));
if (io_status_.ok()) {
heap_buf_ = CacheAllocationPtr(buf.release());
used_buf_ = heap_buf_.get();
slice_ = Slice(heap_buf_.get(), block_size_);
ProcessTrailerIfPresent();
return true;
} else if (!io_status_.IsNotFound() && ioptions_.logger) {
assert(!io_status_.ok());
ROCKS_LOG_INFO(ioptions_.logger,
"Error reading from persistent cache. %s",
io_status_.ToString().c_str());
}
}
return false;
}
inline void BlockFetcher::PrepareBufferForBlockFromFile() {
// cache miss read from device
if ((do_uncompress_ || ioptions_.allow_mmap_reads) &&
block_size_with_trailer_ < kDefaultStackBufferSize) {
// If we've got a small enough chunk of data, read it in to the
// trivially allocated stack buffer instead of needing a full malloc()
//
// `GetBlockContents()` cannot return this data as its lifetime is tied to
// this `BlockFetcher`'s lifetime. That is fine because this is only used
// in cases where we do not expect the `GetBlockContents()` result to be the
// same buffer we are assigning here. If we guess incorrectly, there will be
// a heap allocation and memcpy in `GetBlockContents()` to obtain the final
// result. Considering we are eliding a heap allocation here by using the
// stack buffer, the cost of guessing incorrectly here is one extra memcpy.
//
// When `do_uncompress_` is true, we expect the uncompression step will
// allocate heap memory for the final result. However this expectation will
// be wrong if the block turns out to already be uncompressed, which we
// won't know for sure until after reading it.
//
// When `ioptions_.allow_mmap_reads` is true, we do not expect the file
// reader to use the scratch buffer at all, but instead return a pointer
// into the mapped memory. This expectation will be wrong when using a
// file reader that does not implement mmap reads properly.
used_buf_ = &stack_buf_[0];
} else if (maybe_compressed_ && !do_uncompress_) {
compressed_buf_ =
AllocateBlock(block_size_with_trailer_, memory_allocator_compressed_);
used_buf_ = compressed_buf_.get();
} else {
heap_buf_ = AllocateBlock(block_size_with_trailer_, memory_allocator_);
used_buf_ = heap_buf_.get();
}
}
inline void BlockFetcher::InsertCompressedBlockToPersistentCacheIfNeeded() {
if (io_status_.ok() && read_options_.fill_cache &&
cache_options_.persistent_cache &&
cache_options_.persistent_cache->IsCompressed()) {
PersistentCacheHelper::InsertSerialized(cache_options_, handle_, used_buf_,
block_size_with_trailer_);
}
}
inline void BlockFetcher::InsertUncompressedBlockToPersistentCacheIfNeeded() {
if (io_status_.ok() && !got_from_prefetch_buffer_ &&
read_options_.fill_cache && cache_options_.persistent_cache &&
!cache_options_.persistent_cache->IsCompressed()) {
// insert to uncompressed cache
PersistentCacheHelper::InsertUncompressed(cache_options_, handle_,
*contents_);
}
}
inline void BlockFetcher::CopyBufferToHeapBuf() {
assert(used_buf_ != heap_buf_.get());
heap_buf_ = AllocateBlock(block_size_with_trailer_, memory_allocator_);
memcpy(heap_buf_.get(), used_buf_, block_size_with_trailer_);
#ifndef NDEBUG
num_heap_buf_memcpy_++;
#endif
}
inline void BlockFetcher::CopyBufferToCompressedBuf() {
assert(used_buf_ != compressed_buf_.get());
compressed_buf_ =
AllocateBlock(block_size_with_trailer_, memory_allocator_compressed_);
memcpy(compressed_buf_.get(), used_buf_, block_size_with_trailer_);
#ifndef NDEBUG
num_compressed_buf_memcpy_++;
#endif
}
// Entering this method means the block is not compressed or do not need to be
// uncompressed. The block can be in one of the following buffers:
// 1. prefetch buffer if prefetch is enabled and the block is prefetched before
// 2. stack_buf_ if block size is smaller than the stack_buf_ size and block
// is not compressed
// 3. heap_buf_ if the block is not compressed
// 4. compressed_buf_ if the block is compressed
// 5. direct_io_buf_ if direct IO is enabled
// After this method, if the block is compressed, it should be in
// compressed_buf_, otherwise should be in heap_buf_.
inline void BlockFetcher::GetBlockContents() {
if (slice_.data() != used_buf_) {
// the slice content is not the buffer provided
*contents_ = BlockContents(Slice(slice_.data(), block_size_));
} else {
// page can be either uncompressed or compressed, the buffer either stack
// or heap provided. Refer to https://github.com/facebook/rocksdb/pull/4096
if (got_from_prefetch_buffer_ || used_buf_ == &stack_buf_[0]) {
CopyBufferToHeapBuf();
} else if (used_buf_ == compressed_buf_.get()) {
if (compression_type_ == kNoCompression &&
memory_allocator_ != memory_allocator_compressed_) {
CopyBufferToHeapBuf();
} else {
heap_buf_ = std::move(compressed_buf_);
}
} else if (direct_io_buf_.get() != nullptr) {
if (compression_type_ == kNoCompression) {
CopyBufferToHeapBuf();
} else {
CopyBufferToCompressedBuf();
heap_buf_ = std::move(compressed_buf_);
}
}
*contents_ = BlockContents(std::move(heap_buf_), block_size_);
}
#ifndef NDEBUG
contents_->has_trailer = footer_.GetBlockTrailerSize() > 0;
#endif
}
IOStatus BlockFetcher::ReadBlockContents() {
if (TryGetUncompressBlockFromPersistentCache()) {
compression_type_ = kNoCompression;
#ifndef NDEBUG
contents_->has_trailer = footer_.GetBlockTrailerSize() > 0;
#endif // NDEBUG
return IOStatus::OK();
}
if (TryGetFromPrefetchBuffer()) {
if (!io_status_.ok()) {
return io_status_;
}
} else if (!TryGetSerializedBlockFromPersistentCache()) {
IOOptions opts;
io_status_ = file_->PrepareIOOptions(read_options_, opts);
// Actual file read
if (io_status_.ok()) {
if (file_->use_direct_io()) {
PERF_TIMER_GUARD(block_read_time);
PERF_CPU_TIMER_GUARD(block_read_cpu_time, nullptr);
io_status_ = file_->Read(
opts, handle_.offset(), block_size_with_trailer_, &slice_, nullptr,
&direct_io_buf_, read_options_.rate_limiter_priority);
PERF_COUNTER_ADD(block_read_count, 1);
used_buf_ = const_cast<char*>(slice_.data());
} else {
PrepareBufferForBlockFromFile();
PERF_TIMER_GUARD(block_read_time);
PERF_CPU_TIMER_GUARD(block_read_cpu_time, nullptr);
io_status_ = file_->Read(opts, handle_.offset(),
block_size_with_trailer_, &slice_, used_buf_,
nullptr, read_options_.rate_limiter_priority);
PERF_COUNTER_ADD(block_read_count, 1);
#ifndef NDEBUG
if (slice_.data() == &stack_buf_[0]) {
num_stack_buf_memcpy_++;
} else if (slice_.data() == heap_buf_.get()) {
num_heap_buf_memcpy_++;
} else if (slice_.data() == compressed_buf_.get()) {
num_compressed_buf_memcpy_++;
}
#endif
}
}
// TODO: introduce dedicated perf counter for range tombstones
switch (block_type_) {
case BlockType::kFilter:
case BlockType::kFilterPartitionIndex:
PERF_COUNTER_ADD(filter_block_read_count, 1);
break;
case BlockType::kCompressionDictionary:
PERF_COUNTER_ADD(compression_dict_block_read_count, 1);
break;
case BlockType::kIndex:
PERF_COUNTER_ADD(index_block_read_count, 1);
break;
// Nothing to do here as we don't have counters for the other types.
default:
break;
}
PERF_COUNTER_ADD(block_read_byte, block_size_with_trailer_);
if (!io_status_.ok()) {
return io_status_;
}
if (slice_.size() != block_size_with_trailer_) {
return IOStatus::Corruption(
"truncated block read from " + file_->file_name() + " offset " +
std::to_string(handle_.offset()) + ", expected " +
std::to_string(block_size_with_trailer_) + " bytes, got " +
std::to_string(slice_.size()));
}
ProcessTrailerIfPresent();
if (io_status_.ok()) {
InsertCompressedBlockToPersistentCacheIfNeeded();
} else {
return io_status_;
}
}
if (do_uncompress_ && compression_type_ != kNoCompression) {
PERF_TIMER_GUARD(block_decompress_time);
// compressed page, uncompress, update cache
UncompressionContext context(compression_type_);
UncompressionInfo info(context, uncompression_dict_, compression_type_);
io_status_ = status_to_io_status(UncompressSerializedBlock(
info, slice_.data(), block_size_, contents_, footer_.format_version(),
ioptions_, memory_allocator_));
#ifndef NDEBUG
num_heap_buf_memcpy_++;
#endif
compression_type_ = kNoCompression;
} else {
GetBlockContents();
}
InsertUncompressedBlockToPersistentCacheIfNeeded();
return io_status_;
}
IOStatus BlockFetcher::ReadAsyncBlockContents() {
if (TryGetUncompressBlockFromPersistentCache()) {
compression_type_ = kNoCompression;
#ifndef NDEBUG
contents_->has_trailer = footer_.GetBlockTrailerSize() > 0;
#endif // NDEBUG
return IOStatus::OK();
} else if (!TryGetSerializedBlockFromPersistentCache()) {
assert(prefetch_buffer_ != nullptr);
if (!for_compaction_) {
IOOptions opts;
IOStatus io_s = file_->PrepareIOOptions(read_options_, opts);
if (!io_s.ok()) {
return io_s;
}
io_s = status_to_io_status(prefetch_buffer_->PrefetchAsync(
opts, file_, handle_.offset(), block_size_with_trailer_, &slice_));
if (io_s.IsTryAgain()) {
return io_s;
}
if (io_s.ok()) {
// Data Block is already in prefetch.
got_from_prefetch_buffer_ = true;
ProcessTrailerIfPresent();
if (!io_status_.ok()) {
return io_status_;
}
used_buf_ = const_cast<char*>(slice_.data());
if (do_uncompress_ && compression_type_ != kNoCompression) {
PERF_TIMER_GUARD(block_decompress_time);
// compressed page, uncompress, update cache
UncompressionContext context(compression_type_);
UncompressionInfo info(context, uncompression_dict_,
compression_type_);
io_status_ = status_to_io_status(UncompressSerializedBlock(
info, slice_.data(), block_size_, contents_,
footer_.format_version(), ioptions_, memory_allocator_));
#ifndef NDEBUG
num_heap_buf_memcpy_++;
#endif
compression_type_ = kNoCompression;
} else {
GetBlockContents();
}
InsertUncompressedBlockToPersistentCacheIfNeeded();
return io_status_;
}
}
// Fallback to sequential reading of data blocks in case of io_s returns
// error or for_compaction_is true.
return ReadBlockContents();
}
return io_status_;
}
} // namespace ROCKSDB_NAMESPACE