block_fetcher.cc
// 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 <cinttypes>
#include <string>
#include "logging/logging.h"
#include "memory/memory_allocator.h"
#include "monitoring/perf_context_imp.h"
#include "rocksdb/env.h"
#include "table/block_based/block.h"
#include "table/block_based/block_based_table_reader.h"
#include "table/format.h"
#include "table/persistent_cache_helper.h"
#include "util/coding.h"
#include "util/compression.h"
#include "util/crc32c.h"
#include "util/file_reader_writer.h"
#include "util/stop_watch.h"
#include "util/string_util.h"
#include "util/xxhash.h"
namespace rocksdb {
inline void BlockFetcher::CheckBlockChecksum() {
// Check the crc of the type and the block contents
if (read_options_.verify_checksums) {
const char* data = slice_.data(); // Pointer to where Read put the data
PERF_TIMER_GUARD(block_checksum_time);
uint32_t value = DecodeFixed32(data + block_size_ + 1);
uint32_t actual = 0;
switch (footer_.checksum()) {
case kNoChecksum:
break;
case kCRC32c:
value = crc32c::Unmask(value);
actual = crc32c::Value(data, block_size_ + 1);
break;
case kxxHash:
actual = XXH32(data, static_cast<int>(block_size_) + 1, 0);
break;
case kxxHash64:
actual = static_cast<uint32_t>(
XXH64(data, static_cast<int>(block_size_) + 1, 0) &
uint64_t{0xffffffff});
break;
default:
status_ = Status::Corruption(
"unknown checksum type " + ToString(footer_.checksum()) + " in " +
file_->file_name() + " offset " + ToString(handle_.offset()) +
" size " + ToString(block_size_));
}
if (status_.ok() && actual != value) {
status_ = Status::Corruption(
"block checksum mismatch: expected " + ToString(actual) + ", got " +
ToString(value) + " in " + file_->file_name() + " offset " +
ToString(handle_.offset()) + " size " + ToString(block_size_));
}
}
}
inline bool BlockFetcher::TryGetUncompressBlockFromPersistentCache() {
if (cache_options_.persistent_cache &&
!cache_options_.persistent_cache->IsCompressed()) {
Status status = PersistentCacheHelper::LookupUncompressedPage(
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_.info_log && !status.IsNotFound()) {
assert(!status.ok());
ROCKS_LOG_INFO(ioptions_.info_log,
"Error reading from persistent cache. %s",
status.ToString().c_str());
}
}
}
return false;
}
inline bool BlockFetcher::TryGetFromPrefetchBuffer() {
if (prefetch_buffer_ != nullptr &&
prefetch_buffer_->TryReadFromCache(
handle_.offset(),
static_cast<size_t>(handle_.size()) + kBlockTrailerSize, &slice_,
for_compaction_)) {
block_size_ = static_cast<size_t>(handle_.size());
CheckBlockChecksum();
if (!status_.ok()) {
return true;
}
got_from_prefetch_buffer_ = true;
used_buf_ = const_cast<char*>(slice_.data());
}
return got_from_prefetch_buffer_;
}
inline bool BlockFetcher::TryGetCompressedBlockFromPersistentCache() {
if (cache_options_.persistent_cache &&
cache_options_.persistent_cache->IsCompressed()) {
// lookup uncompressed cache mode p-cache
std::unique_ptr<char[]> raw_data;
status_ = PersistentCacheHelper::LookupRawPage(
cache_options_, handle_, &raw_data, block_size_ + kBlockTrailerSize);
if (status_.ok()) {
heap_buf_ = CacheAllocationPtr(raw_data.release());
used_buf_ = heap_buf_.get();
slice_ = Slice(heap_buf_.get(), block_size_);
return true;
} else if (!status_.IsNotFound() && ioptions_.info_log) {
assert(!status_.ok());
ROCKS_LOG_INFO(ioptions_.info_log,
"Error reading from persistent cache. %s",
status_.ToString().c_str());
}
}
return false;
}
inline void BlockFetcher::PrepareBufferForBlockFromFile() {
// cache miss read from device
if (do_uncompress_ &&
block_size_ + kBlockTrailerSize < kDefaultStackBufferSize) {
// If we've got a small enough hunk of data, read it in to the
// trivially allocated stack buffer instead of needing a full malloc()
used_buf_ = &stack_buf_[0];
} else if (maybe_compressed_ && !do_uncompress_) {
compressed_buf_ = AllocateBlock(block_size_ + kBlockTrailerSize,
memory_allocator_compressed_);
used_buf_ = compressed_buf_.get();
} else {
heap_buf_ =
AllocateBlock(block_size_ + kBlockTrailerSize, memory_allocator_);
used_buf_ = heap_buf_.get();
}
}
inline void BlockFetcher::InsertCompressedBlockToPersistentCacheIfNeeded() {
if (status_.ok() && read_options_.fill_cache &&
cache_options_.persistent_cache &&
cache_options_.persistent_cache->IsCompressed()) {
// insert to raw cache
PersistentCacheHelper::InsertRawPage(cache_options_, handle_, used_buf_,
block_size_ + kBlockTrailerSize);
}
}
inline void BlockFetcher::InsertUncompressedBlockToPersistentCacheIfNeeded() {
if (status_.ok() && !got_from_prefetch_buffer_ && read_options_.fill_cache &&
cache_options_.persistent_cache &&
!cache_options_.persistent_cache->IsCompressed()) {
// insert to uncompressed cache
PersistentCacheHelper::InsertUncompressedPage(cache_options_, handle_,
*contents_);
}
}
inline void BlockFetcher::CopyBufferToHeap() {
assert(used_buf_ != heap_buf_.get());
heap_buf_ = AllocateBlock(block_size_ + kBlockTrailerSize, memory_allocator_);
memcpy(heap_buf_.get(), used_buf_, block_size_ + kBlockTrailerSize);
}
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]) {
CopyBufferToHeap();
} else if (used_buf_ == compressed_buf_.get()) {
if (compression_type_ == kNoCompression &&
memory_allocator_ != memory_allocator_compressed_) {
CopyBufferToHeap();
} else {
heap_buf_ = std::move(compressed_buf_);
}
}
*contents_ = BlockContents(std::move(heap_buf_), block_size_);
}
#ifndef NDEBUG
contents_->is_raw_block = true;
#endif
}
Status BlockFetcher::ReadBlockContents() {
block_size_ = static_cast<size_t>(handle_.size());
if (TryGetUncompressBlockFromPersistentCache()) {
compression_type_ = kNoCompression;
#ifndef NDEBUG
contents_->is_raw_block = true;
#endif // NDEBUG
return Status::OK();
}
if (TryGetFromPrefetchBuffer()) {
if (!status_.ok()) {
return status_;
}
} else if (!TryGetCompressedBlockFromPersistentCache()) {
PrepareBufferForBlockFromFile();
Status s;
{
PERF_TIMER_GUARD(block_read_time);
// Actual file read
status_ = file_->Read(handle_.offset(), block_size_ + kBlockTrailerSize,
&slice_, used_buf_, for_compaction_);
}
PERF_COUNTER_ADD(block_read_count, 1);
// TODO: introduce dedicated perf counter for range tombstones
switch (block_type_) {
case BlockType::kFilter:
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_ + kBlockTrailerSize);
if (!status_.ok()) {
return status_;
}
if (slice_.size() != block_size_ + kBlockTrailerSize) {
return Status::Corruption("truncated block read from " +
file_->file_name() + " offset " +
ToString(handle_.offset()) + ", expected " +
ToString(block_size_ + kBlockTrailerSize) +
" bytes, got " + ToString(slice_.size()));
}
CheckBlockChecksum();
if (status_.ok()) {
InsertCompressedBlockToPersistentCacheIfNeeded();
} else {
return status_;
}
}
PERF_TIMER_GUARD(block_decompress_time);
compression_type_ = get_block_compression_type(slice_.data(), block_size_);
if (do_uncompress_ && compression_type_ != kNoCompression) {
// compressed page, uncompress, update cache
UncompressionContext context(compression_type_);
UncompressionInfo info(context, uncompression_dict_, compression_type_);
status_ = UncompressBlockContents(info, slice_.data(), block_size_,
contents_, footer_.version(), ioptions_,
memory_allocator_);
compression_type_ = kNoCompression;
} else {
GetBlockContents();
}
InsertUncompressedBlockToPersistentCacheIfNeeded();
return status_;
}
} // namespace rocksdb