rocksdb/trace_replay/block_cache_tracer.cc

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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).
#include "trace_replay/block_cache_tracer.h"
#include <cinttypes>
#include <cstdio>
#include <cstdlib>
#include "db/db_impl/db_impl.h"
#include "db/dbformat.h"
#include "rocksdb/slice.h"
#include "util/coding.h"
#include "util/hash.h"
#include "util/string_util.h"
namespace ROCKSDB_NAMESPACE {
namespace {
Block cache tracing: Fix minor bugs with downsampling and some benchmark results. (#5473) Summary: As the code changes for block cache tracing are almost complete, I did a benchmark to compare the performance when block cache tracing is enabled/disabled. With 1% downsampling ratio, the performance overhead of block cache tracing is negligible. When we trace all block accesses, the throughput drops by 6 folds with 16 threads issuing random reads and all reads are served in block cache. Setup: RocksDB: version 6.2 Date: Mon Jun 17 17:11:13 2019 CPU: 24 * Intel Core Processor (Skylake) CPUCache: 16384 KB Keys: 20 bytes each Values: 100 bytes each (100 bytes after compression) Entries: 10000000 Prefix: 20 bytes Keys per prefix: 0 RawSize: 1144.4 MB (estimated) FileSize: 1144.4 MB (estimated) Write rate: 0 bytes/second Read rate: 0 ops/second Compression: NoCompression Compression sampling rate: 0 Memtablerep: skip_list Perf Level: 1 I ran the readrandom workload for 1 minute. Detailed throughput results: (ops/second) Sample rate 0: no block cache tracing. Sample rate 1: trace all block accesses. Sample rate 100: trace accesses 1% blocks. 1 thread |   |   |  -- | -- | -- | -- Sample rate | 0 | 1 | 100 1 MB block cache size | 13,094 | 13,166 | 13,341 10 GB block cache size | 202,243 | 188,677 | 229,182 16 threads |   |   | -- | -- | -- | -- Sample rate | 0 | 1 | 100 1 MB block cache size | 208,761 | 178,700 | 201,872 10 GB block cache size | 2,645,996 | 426,295 | 2,587,605 Pull Request resolved: https://github.com/facebook/rocksdb/pull/5473 Differential Revision: D15869479 Pulled By: HaoyuHuang fbshipit-source-id: 7ae802abe84811281a6af8649f489887cd7c4618
2019-06-18 02:56:09 +02:00
bool ShouldTrace(const Slice& block_key, const TraceOptions& trace_options) {
if (trace_options.sampling_frequency == 0 ||
trace_options.sampling_frequency == 1) {
return true;
}
// We use spatial downsampling so that we have a complete access history for a
// block.
return 0 == GetSliceRangedNPHash(block_key, trace_options.sampling_frequency);
}
} // namespace
const uint64_t kMicrosInSecond = 1000 * 1000;
const uint64_t kSecondInMinute = 60;
const uint64_t kSecondInHour = 3600;
const std::string BlockCacheTraceHelper::kUnknownColumnFamilyName =
"UnknownColumnFamily";
const uint64_t BlockCacheTraceHelper::kReservedGetId = 0;
bool BlockCacheTraceHelper::IsGetOrMultiGetOnDataBlock(
TraceType block_type, TableReaderCaller caller) {
return (block_type == TraceType::kBlockTraceDataBlock) &&
IsGetOrMultiGet(caller);
}
bool BlockCacheTraceHelper::IsGetOrMultiGet(TableReaderCaller caller) {
return caller == TableReaderCaller::kUserGet ||
caller == TableReaderCaller::kUserMultiGet;
}
bool BlockCacheTraceHelper::IsUserAccess(TableReaderCaller caller) {
return caller == TableReaderCaller::kUserGet ||
caller == TableReaderCaller::kUserMultiGet ||
caller == TableReaderCaller::kUserIterator ||
caller == TableReaderCaller::kUserApproximateSize ||
caller == TableReaderCaller::kUserVerifyChecksum;
}
std::string BlockCacheTraceHelper::ComputeRowKey(
const BlockCacheTraceRecord& access) {
if (!IsGetOrMultiGet(access.caller)) {
return "";
}
Slice key = ExtractUserKey(access.referenced_key);
return std::to_string(access.sst_fd_number) + "_" + key.ToString();
}
uint64_t BlockCacheTraceHelper::GetTableId(
const BlockCacheTraceRecord& access) {
if (!IsGetOrMultiGet(access.caller) || access.referenced_key.size() < 4) {
return 0;
}
return static_cast<uint64_t>(DecodeFixed32(access.referenced_key.data())) + 1;
}
uint64_t BlockCacheTraceHelper::GetSequenceNumber(
const BlockCacheTraceRecord& access) {
if (!IsGetOrMultiGet(access.caller)) {
return 0;
}
return access.get_from_user_specified_snapshot == Boolean::kFalse
? 0
: 1 + GetInternalKeySeqno(access.referenced_key);
}
uint64_t BlockCacheTraceHelper::GetBlockOffsetInFile(
const BlockCacheTraceRecord& access) {
Slice input(access.block_key);
uint64_t offset = 0;
while (true) {
uint64_t tmp = 0;
if (GetVarint64(&input, &tmp)) {
offset = tmp;
} else {
break;
}
}
return offset;
}
BlockCacheTraceWriter::BlockCacheTraceWriter(
Env* env, const TraceOptions& trace_options,
std::unique_ptr<TraceWriter>&& trace_writer)
: env_(env),
trace_options_(trace_options),
trace_writer_(std::move(trace_writer)) {}
Status BlockCacheTraceWriter::WriteBlockAccess(
const BlockCacheTraceRecord& record, const Slice& block_key,
const Slice& cf_name, const Slice& referenced_key) {
uint64_t trace_file_size = trace_writer_->GetFileSize();
if (trace_file_size > trace_options_.max_trace_file_size) {
return Status::OK();
}
Trace trace;
trace.ts = record.access_timestamp;
trace.type = record.block_type;
PutLengthPrefixedSlice(&trace.payload, block_key);
PutFixed64(&trace.payload, record.block_size);
PutFixed64(&trace.payload, record.cf_id);
PutLengthPrefixedSlice(&trace.payload, cf_name);
PutFixed32(&trace.payload, record.level);
PutFixed64(&trace.payload, record.sst_fd_number);
trace.payload.push_back(record.caller);
trace.payload.push_back(record.is_cache_hit);
trace.payload.push_back(record.no_insert);
if (BlockCacheTraceHelper::IsGetOrMultiGet(record.caller)) {
PutFixed64(&trace.payload, record.get_id);
trace.payload.push_back(record.get_from_user_specified_snapshot);
PutLengthPrefixedSlice(&trace.payload, referenced_key);
}
if (BlockCacheTraceHelper::IsGetOrMultiGetOnDataBlock(record.block_type,
record.caller)) {
PutFixed64(&trace.payload, record.referenced_data_size);
PutFixed64(&trace.payload, record.num_keys_in_block);
trace.payload.push_back(record.referenced_key_exist_in_block);
}
std::string encoded_trace;
TracerHelper::EncodeTrace(trace, &encoded_trace);
return trace_writer_->Write(encoded_trace);
}
Status BlockCacheTraceWriter::WriteHeader() {
Trace trace;
trace.ts = env_->NowMicros();
trace.type = TraceType::kTraceBegin;
PutLengthPrefixedSlice(&trace.payload, kTraceMagic);
PutFixed32(&trace.payload, kMajorVersion);
PutFixed32(&trace.payload, kMinorVersion);
std::string encoded_trace;
TracerHelper::EncodeTrace(trace, &encoded_trace);
return trace_writer_->Write(encoded_trace);
}
BlockCacheTraceReader::BlockCacheTraceReader(
std::unique_ptr<TraceReader>&& reader)
: trace_reader_(std::move(reader)) {}
Status BlockCacheTraceReader::ReadHeader(BlockCacheTraceHeader* header) {
assert(header != nullptr);
std::string encoded_trace;
Status s = trace_reader_->Read(&encoded_trace);
if (!s.ok()) {
return s;
}
Trace trace;
s = TracerHelper::DecodeTrace(encoded_trace, &trace);
if (!s.ok()) {
return s;
}
header->start_time = trace.ts;
Slice enc_slice = Slice(trace.payload);
Slice magnic_number;
if (!GetLengthPrefixedSlice(&enc_slice, &magnic_number)) {
return Status::Corruption(
"Corrupted header in the trace file: Failed to read the magic number.");
}
if (magnic_number.ToString() != kTraceMagic) {
return Status::Corruption(
"Corrupted header in the trace file: Magic number does not match.");
}
if (!GetFixed32(&enc_slice, &header->rocksdb_major_version)) {
return Status::Corruption(
"Corrupted header in the trace file: Failed to read rocksdb major "
"version number.");
}
if (!GetFixed32(&enc_slice, &header->rocksdb_minor_version)) {
return Status::Corruption(
"Corrupted header in the trace file: Failed to read rocksdb minor "
"version number.");
}
// We should have retrieved all information in the header.
if (!enc_slice.empty()) {
return Status::Corruption(
"Corrupted header in the trace file: The length of header is too "
"long.");
}
return Status::OK();
}
Status BlockCacheTraceReader::ReadAccess(BlockCacheTraceRecord* record) {
assert(record);
std::string encoded_trace;
Status s = trace_reader_->Read(&encoded_trace);
if (!s.ok()) {
return s;
}
Trace trace;
s = TracerHelper::DecodeTrace(encoded_trace, &trace);
if (!s.ok()) {
return s;
}
record->access_timestamp = trace.ts;
record->block_type = trace.type;
Slice enc_slice = Slice(trace.payload);
const unsigned int kCharSize = 1;
Slice block_key;
if (!GetLengthPrefixedSlice(&enc_slice, &block_key)) {
return Status::Incomplete(
"Incomplete access record: Failed to read block key.");
}
record->block_key = block_key.ToString();
if (!GetFixed64(&enc_slice, &record->block_size)) {
return Status::Incomplete(
"Incomplete access record: Failed to read block size.");
}
if (!GetFixed64(&enc_slice, &record->cf_id)) {
return Status::Incomplete(
"Incomplete access record: Failed to read column family ID.");
}
Slice cf_name;
if (!GetLengthPrefixedSlice(&enc_slice, &cf_name)) {
return Status::Incomplete(
"Incomplete access record: Failed to read column family name.");
}
record->cf_name = cf_name.ToString();
if (!GetFixed32(&enc_slice, &record->level)) {
return Status::Incomplete(
"Incomplete access record: Failed to read level.");
}
if (!GetFixed64(&enc_slice, &record->sst_fd_number)) {
return Status::Incomplete(
"Incomplete access record: Failed to read SST file number.");
}
if (enc_slice.empty()) {
return Status::Incomplete(
"Incomplete access record: Failed to read caller.");
}
record->caller = static_cast<TableReaderCaller>(enc_slice[0]);
enc_slice.remove_prefix(kCharSize);
if (enc_slice.empty()) {
return Status::Incomplete(
"Incomplete access record: Failed to read is_cache_hit.");
}
record->is_cache_hit = static_cast<Boolean>(enc_slice[0]);
enc_slice.remove_prefix(kCharSize);
if (enc_slice.empty()) {
return Status::Incomplete(
"Incomplete access record: Failed to read no_insert.");
}
record->no_insert = static_cast<Boolean>(enc_slice[0]);
enc_slice.remove_prefix(kCharSize);
if (BlockCacheTraceHelper::IsGetOrMultiGet(record->caller)) {
if (!GetFixed64(&enc_slice, &record->get_id)) {
return Status::Incomplete(
"Incomplete access record: Failed to read the get id.");
}
if (enc_slice.empty()) {
return Status::Incomplete(
"Incomplete access record: Failed to read "
"get_from_user_specified_snapshot.");
}
record->get_from_user_specified_snapshot =
static_cast<Boolean>(enc_slice[0]);
enc_slice.remove_prefix(kCharSize);
Slice referenced_key;
if (!GetLengthPrefixedSlice(&enc_slice, &referenced_key)) {
return Status::Incomplete(
"Incomplete access record: Failed to read the referenced key.");
}
record->referenced_key = referenced_key.ToString();
}
if (BlockCacheTraceHelper::IsGetOrMultiGetOnDataBlock(record->block_type,
record->caller)) {
if (!GetFixed64(&enc_slice, &record->referenced_data_size)) {
return Status::Incomplete(
"Incomplete access record: Failed to read the referenced data size.");
}
if (!GetFixed64(&enc_slice, &record->num_keys_in_block)) {
return Status::Incomplete(
"Incomplete access record: Failed to read the number of keys in the "
"block.");
}
if (enc_slice.empty()) {
return Status::Incomplete(
"Incomplete access record: Failed to read "
"referenced_key_exist_in_block.");
}
record->referenced_key_exist_in_block = static_cast<Boolean>(enc_slice[0]);
}
return Status::OK();
}
BlockCacheHumanReadableTraceWriter::~BlockCacheHumanReadableTraceWriter() {
if (human_readable_trace_file_writer_) {
human_readable_trace_file_writer_->Flush().PermitUncheckedError();
human_readable_trace_file_writer_->Close().PermitUncheckedError();
}
}
Status BlockCacheHumanReadableTraceWriter::NewWritableFile(
const std::string& human_readable_trace_file_path,
ROCKSDB_NAMESPACE::Env* env) {
if (human_readable_trace_file_path.empty()) {
return Status::InvalidArgument(
"The provided human_readable_trace_file_path is null.");
}
return env->NewWritableFile(human_readable_trace_file_path,
&human_readable_trace_file_writer_, EnvOptions());
}
Status BlockCacheHumanReadableTraceWriter::WriteHumanReadableTraceRecord(
const BlockCacheTraceRecord& access, uint64_t block_id,
uint64_t get_key_id) {
if (!human_readable_trace_file_writer_) {
return Status::OK();
}
int ret = snprintf(
trace_record_buffer_, sizeof(trace_record_buffer_),
"%" PRIu64 ",%" PRIu64 ",%u,%" PRIu64 ",%" PRIu64 ",%s,%" PRIu32
",%" PRIu64 ",%u,%u,%" PRIu64 ",%" PRIu64 ",%" PRIu64 ",%u,%u,%" PRIu64
",%" PRIu64 ",%" PRIu64 ",%" PRIu64 ",%" PRIu64 ",%" PRIu64 "\n",
access.access_timestamp, block_id, access.block_type, access.block_size,
access.cf_id, access.cf_name.c_str(), access.level, access.sst_fd_number,
access.caller, access.no_insert, access.get_id, get_key_id,
access.referenced_data_size, access.is_cache_hit,
access.referenced_key_exist_in_block, access.num_keys_in_block,
BlockCacheTraceHelper::GetTableId(access),
BlockCacheTraceHelper::GetSequenceNumber(access),
static_cast<uint64_t>(access.block_key.size()),
static_cast<uint64_t>(access.referenced_key.size()),
BlockCacheTraceHelper::GetBlockOffsetInFile(access));
if (ret < 0) {
return Status::IOError("failed to format the output");
}
std::string printout(trace_record_buffer_);
return human_readable_trace_file_writer_->Append(printout);
}
BlockCacheHumanReadableTraceReader::BlockCacheHumanReadableTraceReader(
const std::string& trace_file_path)
: BlockCacheTraceReader(/*trace_reader=*/nullptr) {
human_readable_trace_reader_.open(trace_file_path, std::ifstream::in);
}
BlockCacheHumanReadableTraceReader::~BlockCacheHumanReadableTraceReader() {
human_readable_trace_reader_.close();
}
Status BlockCacheHumanReadableTraceReader::ReadHeader(
BlockCacheTraceHeader* /*header*/) {
return Status::OK();
}
Status BlockCacheHumanReadableTraceReader::ReadAccess(
BlockCacheTraceRecord* record) {
std::string line;
if (!std::getline(human_readable_trace_reader_, line)) {
return Status::Incomplete("No more records to read.");
}
std::stringstream ss(line);
std::vector<std::string> record_strs;
while (ss.good()) {
std::string substr;
getline(ss, substr, ',');
record_strs.push_back(substr);
}
if (record_strs.size() != 21) {
return Status::Incomplete("Records format is wrong.");
}
record->access_timestamp = ParseUint64(record_strs[0]);
uint64_t block_key = ParseUint64(record_strs[1]);
record->block_type = static_cast<TraceType>(ParseUint64(record_strs[2]));
record->block_size = ParseUint64(record_strs[3]);
record->cf_id = ParseUint64(record_strs[4]);
record->cf_name = record_strs[5];
record->level = static_cast<uint32_t>(ParseUint64(record_strs[6]));
record->sst_fd_number = ParseUint64(record_strs[7]);
record->caller = static_cast<TableReaderCaller>(ParseUint64(record_strs[8]));
record->no_insert = static_cast<Boolean>(ParseUint64(record_strs[9]));
record->get_id = ParseUint64(record_strs[10]);
uint64_t get_key_id = ParseUint64(record_strs[11]);
record->referenced_data_size = ParseUint64(record_strs[12]);
record->is_cache_hit = static_cast<Boolean>(ParseUint64(record_strs[13]));
record->referenced_key_exist_in_block =
static_cast<Boolean>(ParseUint64(record_strs[14]));
record->num_keys_in_block = ParseUint64(record_strs[15]);
uint64_t table_id = ParseUint64(record_strs[16]);
if (table_id > 0) {
// Decrement since valid table id in the trace file equals traced table id
// + 1.
table_id -= 1;
}
uint64_t get_sequence_number = ParseUint64(record_strs[17]);
if (get_sequence_number > 0) {
record->get_from_user_specified_snapshot = Boolean::kTrue;
// Decrement since valid seq number in the trace file equals traced seq
// number + 1.
get_sequence_number -= 1;
}
uint64_t block_key_size = ParseUint64(record_strs[18]);
uint64_t get_key_size = ParseUint64(record_strs[19]);
uint64_t block_offset = ParseUint64(record_strs[20]);
std::string tmp_block_key;
PutVarint64(&tmp_block_key, block_key);
PutVarint64(&tmp_block_key, block_offset);
// Append 1 until the size is the same as traced block key size.
while (record->block_key.size() < block_key_size - tmp_block_key.size()) {
record->block_key += "1";
}
record->block_key += tmp_block_key;
if (get_key_id != 0) {
std::string tmp_get_key;
PutFixed64(&tmp_get_key, get_key_id);
PutFixed64(&tmp_get_key, get_sequence_number << 8);
PutFixed32(&record->referenced_key, static_cast<uint32_t>(table_id));
// Append 1 until the size is the same as traced key size.
while (record->referenced_key.size() < get_key_size - tmp_get_key.size()) {
record->referenced_key += "1";
}
record->referenced_key += tmp_get_key;
}
return Status::OK();
}
BlockCacheTracer::BlockCacheTracer() { writer_.store(nullptr); }
BlockCacheTracer::~BlockCacheTracer() { EndTrace(); }
Status BlockCacheTracer::StartTrace(
Env* env, const TraceOptions& trace_options,
std::unique_ptr<TraceWriter>&& trace_writer) {
InstrumentedMutexLock lock_guard(&trace_writer_mutex_);
if (writer_.load()) {
return Status::Busy();
}
get_id_counter_.store(1);
trace_options_ = trace_options;
writer_.store(
new BlockCacheTraceWriter(env, trace_options, std::move(trace_writer)));
return writer_.load()->WriteHeader();
}
void BlockCacheTracer::EndTrace() {
InstrumentedMutexLock lock_guard(&trace_writer_mutex_);
if (!writer_.load()) {
return;
}
delete writer_.load();
writer_.store(nullptr);
}
Status BlockCacheTracer::WriteBlockAccess(const BlockCacheTraceRecord& record,
const Slice& block_key,
const Slice& cf_name,
const Slice& referenced_key) {
Block cache tracing: Fix minor bugs with downsampling and some benchmark results. (#5473) Summary: As the code changes for block cache tracing are almost complete, I did a benchmark to compare the performance when block cache tracing is enabled/disabled. With 1% downsampling ratio, the performance overhead of block cache tracing is negligible. When we trace all block accesses, the throughput drops by 6 folds with 16 threads issuing random reads and all reads are served in block cache. Setup: RocksDB: version 6.2 Date: Mon Jun 17 17:11:13 2019 CPU: 24 * Intel Core Processor (Skylake) CPUCache: 16384 KB Keys: 20 bytes each Values: 100 bytes each (100 bytes after compression) Entries: 10000000 Prefix: 20 bytes Keys per prefix: 0 RawSize: 1144.4 MB (estimated) FileSize: 1144.4 MB (estimated) Write rate: 0 bytes/second Read rate: 0 ops/second Compression: NoCompression Compression sampling rate: 0 Memtablerep: skip_list Perf Level: 1 I ran the readrandom workload for 1 minute. Detailed throughput results: (ops/second) Sample rate 0: no block cache tracing. Sample rate 1: trace all block accesses. Sample rate 100: trace accesses 1% blocks. 1 thread |   |   |  -- | -- | -- | -- Sample rate | 0 | 1 | 100 1 MB block cache size | 13,094 | 13,166 | 13,341 10 GB block cache size | 202,243 | 188,677 | 229,182 16 threads |   |   | -- | -- | -- | -- Sample rate | 0 | 1 | 100 1 MB block cache size | 208,761 | 178,700 | 201,872 10 GB block cache size | 2,645,996 | 426,295 | 2,587,605 Pull Request resolved: https://github.com/facebook/rocksdb/pull/5473 Differential Revision: D15869479 Pulled By: HaoyuHuang fbshipit-source-id: 7ae802abe84811281a6af8649f489887cd7c4618
2019-06-18 02:56:09 +02:00
if (!writer_.load() || !ShouldTrace(block_key, trace_options_)) {
return Status::OK();
}
InstrumentedMutexLock lock_guard(&trace_writer_mutex_);
if (!writer_.load()) {
return Status::OK();
}
return writer_.load()->WriteBlockAccess(record, block_key, cf_name,
referenced_key);
}
uint64_t BlockCacheTracer::NextGetId() {
if (!writer_.load(std::memory_order_relaxed)) {
return BlockCacheTraceHelper::kReservedGetId;
}
uint64_t prev_value = get_id_counter_.fetch_add(1);
if (prev_value == BlockCacheTraceHelper::kReservedGetId) {
// fetch and add again.
return get_id_counter_.fetch_add(1);
}
return prev_value;
}
} // namespace ROCKSDB_NAMESPACE