mirror of https://github.com/facebook/rocksdb.git
Add a utility function to guess optimized options based on constraints
Summary: Add a function GetOptions(), where based on four parameters users give: read/write amplification threshold, memory budget for mem tables and target DB size, it picks up a compaction style and parameters for them. Background threads are not touched yet. One limit of this algorithm: since compression rate and key/value size are hard to predict, it's hard to predict level 0 file size from write buffer size. Simply make 1:1 ratio here. Sample results: https://reviews.facebook.net/P477 Test Plan: Will add some a unit test where some sample scenarios are given and see they pick the results that make sense Reviewers: yhchiang, dhruba, haobo, igor, ljin Reviewed By: ljin Subscribers: leveldb Differential Revision: https://reviews.facebook.net/D18741
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11
Makefile
11
Makefile
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@ -114,9 +114,10 @@ TESTS = \
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deletefile_test \
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table_test \
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thread_local_test \
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geodb_test \
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rate_limiter_test \
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cuckoo_table_builder_test
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geodb_test \
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rate_limiter_test \
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cuckoo_table_builder_test \
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options_test
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TOOLS = \
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sst_dump \
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@ -124,6 +125,7 @@ TOOLS = \
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db_stress \
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ldb \
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db_repl_stress \
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options_test \
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blob_store_bench
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PROGRAMS = db_bench signal_test table_reader_bench log_and_apply_bench $(TOOLS)
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@ -414,6 +416,9 @@ geodb_test: utilities/geodb/geodb_test.o $(LIBOBJECTS) $(TESTHARNESS)
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cuckoo_table_builder_test: table/cuckoo_table_builder_test.o $(LIBOBJECTS) $(TESTHARNESS)
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$(CXX) table/cuckoo_table_builder_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)
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options_test: util/options_test.o $(LIBOBJECTS) $(TESTHARNESS)
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$(CXX) util/options_test.o $(LIBOBJECTS) $(TESTHARNESS) $(EXEC_LDFLAGS) -o $@ $(LDFLAGS) $(COVERAGEFLAGS)
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$(MEMENVLIBRARY) : $(MEMENVOBJECTS)
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rm -f $@
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$(AR) -rs $@ $(MEMENVOBJECTS)
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@ -1027,7 +1027,6 @@ struct FlushOptions {
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FlushOptions() : wait(true) {}
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};
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// Create a RateLimiter object, which can be shared among RocksDB instances to
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// control write rate of flush and compaction.
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// @rate_bytes_per_sec: this is the only parameter you want to set most of the
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@ -1051,7 +1050,16 @@ extern RateLimiter* NewRateLimiter(
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int64_t refill_period_us = 100 * 1000,
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int32_t fairness = 10);
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// Get options based on some guidelines. Now only tune parameter based on
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// flush/compaction and fill default parameters for other parameters.
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// total_write_buffer_limit: budget for memory spent for mem tables
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// read_amplification_threshold: comfortable value of read amplification
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// write_amplification_threshold: comfortable value of write amplification.
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// target_db_size: estimated total DB size.
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extern Options GetOptions(size_t total_write_buffer_limit,
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int read_amplification_threshold = 8,
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int write_amplification_threshold = 32,
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uint64_t target_db_size = 68719476736 /* 64GB */);
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} // namespace rocksdb
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#endif // STORAGE_ROCKSDB_INCLUDE_OPTIONS_H_
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@ -0,0 +1,196 @@
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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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#include <math.h>
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#include <algorithm>
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#include "rocksdb/options.h"
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namespace rocksdb {
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namespace {
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// For now, always use 1-0 as level bytes multiplier.
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const int kBytesForLevelMultiplier = 10;
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const size_t kBytesForOneMb = 1024 * 1024;
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// Pick compaction style
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CompactionStyle PickCompactionStyle(size_t write_buffer_size,
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int read_amp_threshold,
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int write_amp_threshold,
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uint64_t target_db_size) {
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// Estimate read amplification and write amplification of two compaction
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// styles. If there is hard limit to force a choice, make the choice.
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// Otherwise, calculate a score based on threshold and expected value of
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// two styles, weighing reads 4X important than writes.
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int expected_levels = static_cast<int>(ceil(
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log(target_db_size / write_buffer_size) / log(kBytesForLevelMultiplier)));
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int expected_max_files_universal =
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static_cast<int>(ceil(log2(target_db_size / write_buffer_size)));
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const int kEstimatedLevel0FilesInLevelStyle = 2;
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// Estimate write amplification:
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// (1) 1 for every L0 file
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// (2) 2 for L1
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// (3) kBytesForLevelMultiplier for the last level. It's really hard to
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// predict.
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// (3) kBytesForLevelMultiplier for other levels.
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int expected_write_amp_level = kEstimatedLevel0FilesInLevelStyle + 2
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+ (expected_levels - 2) * kBytesForLevelMultiplier
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+ kBytesForLevelMultiplier;
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int expected_read_amp_level =
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kEstimatedLevel0FilesInLevelStyle + expected_levels;
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int max_read_amp_uni = expected_max_files_universal;
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if (read_amp_threshold <= max_read_amp_uni) {
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return kCompactionStyleLevel;
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} else if (write_amp_threshold <= expected_write_amp_level) {
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return kCompactionStyleUniversal;
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}
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const double kReadWriteWeight = 4;
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double level_ratio =
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static_cast<double>(read_amp_threshold) / expected_read_amp_level *
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kReadWriteWeight +
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static_cast<double>(write_amp_threshold) / expected_write_amp_level;
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int expected_write_amp_uni = expected_max_files_universal / 2 + 2;
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int expected_read_amp_uni = expected_max_files_universal / 2 + 1;
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double uni_ratio =
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static_cast<double>(read_amp_threshold) / expected_read_amp_uni *
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kReadWriteWeight +
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static_cast<double>(write_amp_threshold) / expected_write_amp_uni;
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if (level_ratio > uni_ratio) {
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return kCompactionStyleLevel;
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} else {
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return kCompactionStyleUniversal;
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}
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}
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// Pick mem table size
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void PickWriteBufferSize(size_t total_write_buffer_limit, Options* options) {
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const size_t kMaxWriteBufferSize = 128 * kBytesForOneMb;
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const size_t kMinWriteBufferSize = 4 * kBytesForOneMb;
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// Try to pick up a buffer size between 4MB and 128MB.
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// And try to pick 4 as the total number of write buffers.
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size_t write_buffer_size = total_write_buffer_limit / 4;
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if (write_buffer_size > kMaxWriteBufferSize) {
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write_buffer_size = kMaxWriteBufferSize;
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} else if (write_buffer_size < kMinWriteBufferSize) {
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write_buffer_size = std::min(static_cast<size_t>(kMinWriteBufferSize),
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total_write_buffer_limit / 2);
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}
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// Truncate to multiple of 1MB.
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if (write_buffer_size % kBytesForOneMb != 0) {
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write_buffer_size =
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(write_buffer_size / kBytesForOneMb + 1) * kBytesForOneMb;
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}
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options->write_buffer_size = write_buffer_size;
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options->max_write_buffer_number =
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total_write_buffer_limit / write_buffer_size;
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options->min_write_buffer_number_to_merge = 1;
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}
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void OptimizeForUniversal(Options* options) {
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options->level0_file_num_compaction_trigger = 2;
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options->level0_slowdown_writes_trigger = 30;
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options->level0_stop_writes_trigger = 40;
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options->max_open_files = -1;
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}
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// Optimize parameters for level-based compaction
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void OptimizeForLevel(int read_amplification_threshold,
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int write_amplification_threshold,
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uint64_t target_db_size, Options* options) {
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int expected_levels_one_level0_file =
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static_cast<int>(ceil(log(target_db_size / options->write_buffer_size) /
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log(kBytesForLevelMultiplier)));
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int level0_stop_writes_trigger =
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read_amplification_threshold - expected_levels_one_level0_file;
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const size_t kInitialLevel0TotalSize = 128 * kBytesForOneMb;
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const int kMaxFileNumCompactionTrigger = 4;
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const int kMinLevel0StopTrigger = 3;
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int file_num_buffer =
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kInitialLevel0TotalSize / options->write_buffer_size + 1;
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if (level0_stop_writes_trigger > file_num_buffer) {
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// Have sufficient room for multiple level 0 files
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// Try enlarge the buffer up to 1GB
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// Try to enlarge the buffer up to 1GB, if still have sufficient headroom.
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file_num_buffer *=
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std::pow(2, std::max(0, std::min(3, level0_stop_writes_trigger -
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file_num_buffer - 2)));
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options->level0_stop_writes_trigger = level0_stop_writes_trigger;
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options->level0_slowdown_writes_trigger = level0_stop_writes_trigger - 2;
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options->level0_file_num_compaction_trigger =
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std::min(kMaxFileNumCompactionTrigger, file_num_buffer / 2);
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} else {
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options->level0_stop_writes_trigger =
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std::max(kMinLevel0StopTrigger, file_num_buffer);
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options->level0_slowdown_writes_trigger =
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options->level0_stop_writes_trigger - 1;
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options->level0_file_num_compaction_trigger = 1;
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}
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// This doesn't consider compaction and overheads of mem tables. But usually
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// it is in the same order of magnitude.
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int expected_level0_compaction_size =
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options->level0_file_num_compaction_trigger * options->write_buffer_size;
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// Enlarge level1 target file size if level0 compaction size is larger.
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int max_bytes_for_level_base = 10 * kBytesForOneMb;
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if (expected_level0_compaction_size > max_bytes_for_level_base) {
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max_bytes_for_level_base = expected_level0_compaction_size;
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}
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options->max_bytes_for_level_base = max_bytes_for_level_base;
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// Now always set level multiplier to be 10
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options->max_bytes_for_level_multiplier = kBytesForLevelMultiplier;
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const int kMinFileSize = 2 * kBytesForOneMb;
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// Allow at least 3-way parallelism for compaction between level 1 and 2.
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int max_file_size = max_bytes_for_level_base / 3;
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if (max_file_size < kMinFileSize) {
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options->target_file_size_base = kMinFileSize;
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} else {
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if (max_file_size % kBytesForOneMb != 0) {
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max_file_size = (max_file_size / kBytesForOneMb + 1) * kBytesForOneMb;
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}
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options->target_file_size_base = max_file_size;
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}
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// TODO: consider to tune num_levels too.
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}
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} // namespace
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Options GetOptions(size_t total_write_buffer_limit,
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int read_amplification_threshold,
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int write_amplification_threshold, uint64_t target_db_size) {
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Options options;
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PickWriteBufferSize(total_write_buffer_limit, &options);
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size_t write_buffer_size = options.write_buffer_size;
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options.compaction_style =
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PickCompactionStyle(write_buffer_size, read_amplification_threshold,
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write_amplification_threshold, target_db_size);
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if (options.compaction_style == kCompactionStyleUniversal) {
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OptimizeForUniversal(&options);
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} else {
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OptimizeForLevel(read_amplification_threshold,
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write_amplification_threshold, target_db_size, &options);
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}
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return options;
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}
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} // namespace rocksdb
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@ -0,0 +1,80 @@
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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#define __STDC_FORMAT_MACROS
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#include <inttypes.h>
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#include <gflags/gflags.h>
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#include "rocksdb/options.h"
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#include "util/testharness.h"
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using GFLAGS::ParseCommandLineFlags;
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DEFINE_bool(enable_print, false, "Print options generated to console.");
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namespace rocksdb {
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class OptionsTest {};
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class StderrLogger : public Logger {
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public:
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virtual void Logv(const char* format, va_list ap) override {
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vprintf(format, ap);
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printf("\n");
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}
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};
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Options PrintAndGetOptions(size_t total_write_buffer_limit,
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int read_amplification_threshold,
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int write_amplification_threshold,
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uint64_t target_db_size = 68719476736) {
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StderrLogger logger;
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if (FLAGS_enable_print) {
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printf(
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"---- total_write_buffer_limit: %zu "
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"read_amplification_threshold: %d write_amplification_threshold: %d "
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"target_db_size %" PRIu64 " ----\n",
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total_write_buffer_limit, read_amplification_threshold,
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write_amplification_threshold, target_db_size);
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}
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Options options =
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GetOptions(total_write_buffer_limit, read_amplification_threshold,
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write_amplification_threshold, target_db_size);
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if (FLAGS_enable_print) {
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options.Dump(&logger);
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printf("-------------------------------------\n\n\n");
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}
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return options;
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}
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TEST(OptionsTest, LooseCondition) {
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Options options;
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PrintAndGetOptions(static_cast<size_t>(10) * 1024 * 1024 * 1024, 100, 100);
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// Less mem table memory budget
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PrintAndGetOptions(32 * 1024 * 1024, 100, 100);
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// Tight read amplification
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options = PrintAndGetOptions(128 * 1024 * 1024, 8, 100);
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ASSERT_EQ(options.compaction_style, kCompactionStyleLevel);
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// Tight write amplification
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options = PrintAndGetOptions(128 * 1024 * 1024, 64, 10);
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ASSERT_EQ(options.compaction_style, kCompactionStyleUniversal);
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// Both tight amplifications
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PrintAndGetOptions(128 * 1024 * 1024, 4, 8);
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}
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} // namespace rocksdb
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int main(int argc, char** argv) {
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ParseCommandLineFlags(&argc, &argv, true);
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return rocksdb::test::RunAllTests();
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}
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