filter_bench - a prelim tool for SST filter benchmarking (#5825)

Summary:
Example: using the tool before and after PR https://github.com/facebook/rocksdb/issues/5784 shows that
the refactoring, presumed performance-neutral, actually sped up SST
filters by about 3% to 8% (repeatable result):

Before:
-  Dry run ns/op: 22.4725
-  Single filter ns/op: 51.1078
-  Random filter ns/op: 120.133

After:
+  Dry run ns/op: 22.2301
+  Single filter run ns/op: 47.4313
+  Random filter ns/op: 115.9

Only tests filters for the block-based table (full filters and
partitioned filters - same implementation; not block-based filters),
which seems to be the recommended format/implementation.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5825

Differential Revision: D17804987

Pulled By: pdillinger

fbshipit-source-id: 0f18a9c254c57f7866030d03e7fa4ba503bac3c5

CMakeLists.txt

@@ -1046,6 +1046,7 @@ if(WITH_TESTS)
     db/range_del_aggregator_bench.cc
     tools/db_bench.cc
     table/table_reader_bench.cc
+    util/filter_bench.cc
     utilities/persistent_cache/hash_table_bench.cc)
   add_library(testharness OBJECT test_util/testharness.cc)
   foreach(sourcefile ${BENCHMARKS})

Makefile

@@ -649,7 +649,7 @@ TEST_LIBS = \
 	librocksdb_env_basic_test.a
 
 # TODO: add back forward_iterator_bench, after making it build in all environemnts.
-BENCHMARKS = db_bench table_reader_bench cache_bench memtablerep_bench persistent_cache_bench range_del_aggregator_bench
+BENCHMARKS = db_bench table_reader_bench cache_bench memtablerep_bench filter_bench persistent_cache_bench range_del_aggregator_bench
 
 # if user didn't config LIBNAME, set the default
 ifeq ($(LIBNAME),)
@@ -1162,6 +1162,9 @@ persistent_cache_bench: utilities/persistent_cache/persistent_cache_bench.o $(LI
 memtablerep_bench: memtable/memtablerep_bench.o $(LIBOBJECTS) $(TESTUTIL)
 	$(AM_LINK)
 
+filter_bench: util/filter_bench.o $(LIBOBJECTS) $(TESTUTIL)
+	$(AM_LINK)
+
 db_stress: tools/db_stress.o $(LIBOBJECTS) $(TESTUTIL)
 	$(AM_LINK)
 

table/block_based/block_based_filter_block_test.cc

@@ -8,9 +8,9 @@
 // found in the LICENSE file. See the AUTHORS file for names of contributors.
 
 #include "table/block_based/block_based_filter_block.h"
-
 #include "rocksdb/filter_policy.h"
 #include "table/block_based/block_based_table_reader.h"
+#include "table/block_based/mock_block_based_table.h"
 #include "test_util/testharness.h"
 #include "test_util/testutil.h"
 #include "util/coding.h"
@@ -48,28 +48,10 @@ class MockBlockBasedTable : public BlockBasedTable {
       : BlockBasedTable(rep, nullptr /* block_cache_tracer */) {}
 };
 
-class FilterBlockTest : public testing::Test {
+class FilterBlockTest : public mock::MockBlockBasedTableTester,
+                        public testing::Test {
  public:
-  Options options_;
-  ImmutableCFOptions ioptions_;
-  EnvOptions env_options_;
-  BlockBasedTableOptions table_options_;
-  InternalKeyComparator icomp_;
-  std::unique_ptr<BlockBasedTable> table_;
-
-  FilterBlockTest()
-      : ioptions_(options_),
-        env_options_(options_),
-        icomp_(options_.comparator) {
-    table_options_.filter_policy.reset(new TestHashFilter);
-
-    constexpr bool skip_filters = false;
-    constexpr int level = 0;
-    constexpr bool immortal_table = false;
-    table_.reset(new MockBlockBasedTable(
-        new BlockBasedTable::Rep(ioptions_, env_options_, table_options_,
-                                 icomp_, skip_filters, level, immortal_table)));
-  }
+  FilterBlockTest() : mock::MockBlockBasedTableTester(new TestHashFilter) {}
 };
 
 TEST_F(FilterBlockTest, EmptyBuilder) {
@@ -254,28 +236,11 @@ TEST_F(FilterBlockTest, MultiChunk) {
 
 // Test for block based filter block
 // use new interface in FilterPolicy to create filter builder/reader
-class BlockBasedFilterBlockTest : public testing::Test {
+class BlockBasedFilterBlockTest : public mock::MockBlockBasedTableTester,
+                                  public testing::Test {
  public:
-  Options options_;
-  ImmutableCFOptions ioptions_;
-  EnvOptions env_options_;
-  BlockBasedTableOptions table_options_;
-  InternalKeyComparator icomp_;
-  std::unique_ptr<BlockBasedTable> table_;
-
   BlockBasedFilterBlockTest()
-      : ioptions_(options_),
-        env_options_(options_),
-        icomp_(options_.comparator) {
-    table_options_.filter_policy.reset(NewBloomFilterPolicy(10));
-
-    constexpr bool skip_filters = false;
-    constexpr int level = 0;
-    constexpr bool immortal_table = false;
-    table_.reset(new MockBlockBasedTable(
-        new BlockBasedTable::Rep(ioptions_, env_options_, table_options_,
-                                 icomp_, skip_filters, level, immortal_table)));
-  }
+      : mock::MockBlockBasedTableTester(NewBloomFilterPolicy(10)) {}
 };
 
 TEST_F(BlockBasedFilterBlockTest, BlockBasedEmptyBuilder) {

table/block_based/full_filter_block_test.cc

@@ -4,9 +4,9 @@
 //  (found in the LICENSE.Apache file in the root directory).
 
 #include "table/block_based/full_filter_block.h"
-
 #include "rocksdb/filter_policy.h"
 #include "table/block_based/block_based_table_reader.h"
+#include "table/block_based/mock_block_based_table.h"
 #include "table/full_filter_bits_builder.h"
 #include "test_util/testharness.h"
 #include "test_util/testutil.h"
@@ -100,28 +100,11 @@ class TestHashFilter : public FilterPolicy {
   }
 };
 
-class PluginFullFilterBlockTest : public testing::Test {
+class PluginFullFilterBlockTest : public mock::MockBlockBasedTableTester,
+                                  public testing::Test {
  public:
-  Options options_;
-  ImmutableCFOptions ioptions_;
-  EnvOptions env_options_;
-  BlockBasedTableOptions table_options_;
-  InternalKeyComparator icomp_;
-  std::unique_ptr<BlockBasedTable> table_;
-
   PluginFullFilterBlockTest()
-      : ioptions_(options_),
-        env_options_(options_),
-        icomp_(options_.comparator) {
-    table_options_.filter_policy.reset(new TestHashFilter);
-
-    constexpr bool skip_filters = false;
-    constexpr int level = 0;
-    constexpr bool immortal_table = false;
-    table_.reset(new MockBlockBasedTable(
-        new BlockBasedTable::Rep(ioptions_, env_options_, table_options_,
-                                 icomp_, skip_filters, level, immortal_table)));
-  }
+      : mock::MockBlockBasedTableTester(new TestHashFilter) {}
 };
 
 TEST_F(PluginFullFilterBlockTest, PluginEmptyBuilder) {
@@ -193,28 +176,11 @@ TEST_F(PluginFullFilterBlockTest, PluginSingleChunk) {
       /*lookup_context=*/nullptr));
 }
 
-class FullFilterBlockTest : public testing::Test {
+class FullFilterBlockTest : public mock::MockBlockBasedTableTester,
+                            public testing::Test {
  public:
-  Options options_;
-  ImmutableCFOptions ioptions_;
-  EnvOptions env_options_;
-  BlockBasedTableOptions table_options_;
-  InternalKeyComparator icomp_;
-  std::unique_ptr<BlockBasedTable> table_;
-
   FullFilterBlockTest()
-      : ioptions_(options_),
-        env_options_(options_),
-        icomp_(options_.comparator) {
-    table_options_.filter_policy.reset(NewBloomFilterPolicy(10, false));
-
-    constexpr bool skip_filters = false;
-    constexpr int level = 0;
-    constexpr bool immortal_table = false;
-    table_.reset(new MockBlockBasedTable(
-        new BlockBasedTable::Rep(ioptions_, env_options_, table_options_,
-                                 icomp_, skip_filters, level, immortal_table)));
-  }
+      : mock::MockBlockBasedTableTester(NewBloomFilterPolicy(10, false)) {}
 };
 
 TEST_F(FullFilterBlockTest, EmptyBuilder) {

table/block_based/mock_block_based_table.h

@@ -0,0 +1,45 @@
+//  Copyright (c) 2019-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).
+#pragma once
+
+#include "table/block_based/block_based_filter_block.h"
+#include "rocksdb/filter_policy.h"
+#include "table/block_based/block_based_table_reader.h"
+
+namespace rocksdb {
+namespace mock {
+
+class MockBlockBasedTable : public BlockBasedTable {
+ public:
+  explicit MockBlockBasedTable(Rep* rep)
+      : BlockBasedTable(rep, nullptr /* block_cache_tracer */) {}
+};
+
+class MockBlockBasedTableTester {
+ public:
+  Options options_;
+  ImmutableCFOptions ioptions_;
+  EnvOptions env_options_;
+  BlockBasedTableOptions table_options_;
+  InternalKeyComparator icomp_;
+  std::unique_ptr<BlockBasedTable> table_;
+
+  MockBlockBasedTableTester(const FilterPolicy *filter_policy)
+      : ioptions_(options_),
+        env_options_(options_),
+        icomp_(options_.comparator) {
+    table_options_.filter_policy.reset(filter_policy);
+
+    constexpr bool skip_filters = false;
+    constexpr int level = 0;
+    constexpr bool immortal_table = false;
+    table_.reset(new MockBlockBasedTable(
+        new BlockBasedTable::Rep(ioptions_, env_options_, table_options_,
+                                 icomp_, skip_filters, level, immortal_table)));
+  }
+};
+
+}  // namespace mock
+}  // namespace rocksdb

util/filter_bench.cc

@@ -0,0 +1,461 @@
+//  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).
+
+#ifndef GFLAGS
+#include <cstdio>
+int main() {
+  fprintf(stderr, "Please install gflags to run rocksdb tools\n");
+  return 1;
+}
+#else
+
+#include <cinttypes>
+#include <iostream>
+#include <random>
+#include <vector>
+
+#include "port/port.h"
+#include "port/stack_trace.h"
+#include "rocksdb/filter_policy.h"
+#include "table/block_based/full_filter_block.h"
+#include "table/block_based/mock_block_based_table.h"
+#include "util/gflags_compat.h"
+#include "util/hash.h"
+#include "util/stop_watch.h"
+
+using GFLAGS_NAMESPACE::ParseCommandLineFlags;
+using GFLAGS_NAMESPACE::RegisterFlagValidator;
+using GFLAGS_NAMESPACE::SetUsageMessage;
+
+DEFINE_int64(seed, 0, "Seed for random number generators");
+
+DEFINE_double(working_mem_size_mb, 200,
+              "MB of memory to get up to among all filters");
+
+DEFINE_uint32(average_keys_per_filter, 10000,
+              "Average number of keys per filter");
+
+DEFINE_uint32(key_size, 16, "Number of bytes each key should be");
+
+DEFINE_uint32(batch_size, 8, "Number of keys to group in each batch");
+
+DEFINE_uint32(bits_per_key, 10, "Bits per key setting for filters");
+
+DEFINE_double(m_queries, 200, "Millions of queries for each test mode");
+
+DEFINE_bool(use_full_block_reader, false,
+            "Use FullFilterBlockReader interface rather than FilterBitsReader");
+
+DEFINE_bool(quick, false, "Run more limited set of tests, fewer queries");
+
+DEFINE_bool(allow_bad_fp_rate, false, "Continue even if FP rate is bad");
+
+DEFINE_bool(legend, false,
+            "Print more information about interpreting results instead of "
+            "running tests");
+
+void _always_assert_fail(int line, const char *file, const char *expr) {
+  fprintf(stderr, "%s: %d: Assertion %s failed\n", file, line, expr);
+  abort();
+}
+
+#define ALWAYS_ASSERT(cond) \
+  ((cond) ? (void)0 : ::_always_assert_fail(__LINE__, __FILE__, #cond))
+
+using rocksdb::BlockContents;
+using rocksdb::CachableEntry;
+using rocksdb::fastrange32;
+using rocksdb::FilterBitsBuilder;
+using rocksdb::FilterBitsReader;
+using rocksdb::FullFilterBlockReader;
+using rocksdb::Slice;
+using rocksdb::mock::MockBlockBasedTableTester;
+
+struct KeyMaker {
+  KeyMaker(size_t size)
+      : data_(new char[size]),
+        slice_(data_.get(), size),
+        vals_(reinterpret_cast<uint32_t *>(data_.get())) {
+    assert(size >= 8);
+    memset(data_.get(), 0, size);
+  }
+  std::unique_ptr<char[]> data_;
+  Slice slice_;
+  uint32_t *vals_;
+
+  Slice Get(uint32_t filter_num, uint32_t val_num) {
+    vals_[0] = filter_num + val_num;
+    vals_[1] = val_num;
+    return slice_;
+  }
+};
+
+void PrintWarnings() {
+#if defined(__GNUC__) && !defined(__OPTIMIZE__)
+  fprintf(stdout,
+          "WARNING: Optimization is disabled: benchmarks unnecessarily slow\n");
+#endif
+#ifndef NDEBUG
+  fprintf(stdout,
+          "WARNING: Assertions are enabled; benchmarks unnecessarily slow\n");
+#endif
+}
+
+struct FilterInfo {
+  uint32_t filter_id_ = 0;
+  std::unique_ptr<const char[]> owner_;
+  Slice filter_;
+  uint32_t keys_added_ = 0;
+  std::unique_ptr<FilterBitsReader> reader_;
+  std::unique_ptr<FullFilterBlockReader> full_block_reader_;
+  uint64_t outside_queries_ = 0;
+  uint64_t false_positives_ = 0;
+};
+
+enum TestMode {
+  kSingleFilter,
+  kBatchPrepared,
+  kBatchUnprepared,
+  kFiftyOneFilter,
+  kEightyTwentyFilter,
+  kRandomFilter,
+};
+
+static const std::vector<TestMode> allTestModes = {
+    kSingleFilter,   kBatchPrepared,      kBatchUnprepared,
+    kFiftyOneFilter, kEightyTwentyFilter, kRandomFilter,
+};
+
+static const std::vector<TestMode> quickTestModes = {
+    kSingleFilter,
+    kRandomFilter,
+};
+
+const char *TestModeToString(TestMode tm) {
+  switch (tm) {
+    case kSingleFilter:
+      return "Single filter";
+    case kBatchPrepared:
+      return "Batched, prepared";
+    case kBatchUnprepared:
+      return "Batched, unprepared";
+    case kFiftyOneFilter:
+      return "Skewed 50% in 1%";
+    case kEightyTwentyFilter:
+      return "Skewed 80% in 20%";
+    case kRandomFilter:
+      return "Random filter";
+  }
+  return "Bad TestMode";
+}
+
+struct FilterBench : public MockBlockBasedTableTester {
+  std::vector<KeyMaker> kms_;
+  std::vector<FilterInfo> infos_;
+  std::mt19937 random_;
+
+  FilterBench()
+      : MockBlockBasedTableTester(
+            rocksdb::NewBloomFilterPolicy(FLAGS_bits_per_key)),
+        random_(FLAGS_seed) {
+    for (uint32_t i = 0; i < FLAGS_batch_size; ++i) {
+      kms_.emplace_back(FLAGS_key_size < 8 ? 8 : FLAGS_key_size);
+    }
+  }
+
+  void Go();
+
+  void RandomQueryTest(bool inside, bool dry_run, TestMode mode);
+};
+
+void FilterBench::Go() {
+  std::unique_ptr<FilterBitsBuilder> builder(
+      table_options_.filter_policy->GetFilterBitsBuilder());
+
+  uint32_t variance_mask = 1;
+  while (variance_mask * variance_mask * 4 < FLAGS_average_keys_per_filter) {
+    variance_mask = variance_mask * 2 + 1;
+  }
+
+  const std::vector<TestMode> &testModes =
+      FLAGS_quick ? quickTestModes : allTestModes;
+  if (FLAGS_quick) {
+    FLAGS_m_queries /= 10.0;
+  }
+
+  std::cout << "Building..." << std::endl;
+
+  size_t total_memory_used = 0;
+  size_t total_keys_added = 0;
+
+  rocksdb::StopWatchNano timer(rocksdb::Env::Default(), true);
+
+  while (total_memory_used < 1024 * 1024 * FLAGS_working_mem_size_mb) {
+    uint32_t filter_id = random_();
+    uint32_t keys_to_add = FLAGS_average_keys_per_filter +
+                           (random_() & variance_mask) - (variance_mask / 2);
+    for (uint32_t i = 0; i < keys_to_add; ++i) {
+      builder->AddKey(kms_[0].Get(filter_id, i));
+    }
+    infos_.emplace_back();
+    FilterInfo &info = infos_.back();
+    info.filter_id_ = filter_id;
+    info.filter_ = builder->Finish(&info.owner_);
+    info.keys_added_ = keys_to_add;
+    info.reader_.reset(
+        table_options_.filter_policy->GetFilterBitsReader(info.filter_));
+    CachableEntry<BlockContents> block(
+        new BlockContents(info.filter_), nullptr /* cache */,
+        nullptr /* cache_handle */, true /* own_value */);
+    info.full_block_reader_.reset(
+        new FullFilterBlockReader(table_.get(), std::move(block)));
+    total_memory_used += info.filter_.size();
+    total_keys_added += keys_to_add;
+  }
+
+  uint64_t elapsed_nanos = timer.ElapsedNanos();
+  double ns = double(elapsed_nanos) / total_keys_added;
+  std::cout << "Build avg ns/key: " << ns << std::endl;
+  std::cout << "Number of filters: " << infos_.size() << std::endl;
+  std::cout << "Total memory (MB): " << total_memory_used / 1024.0 / 1024.0
+            << std::endl;
+
+  double bpk = total_memory_used * 8.0 / total_keys_added;
+  std::cout << "Bits/key actual: " << bpk << std::endl;
+  if (!FLAGS_quick) {
+    double tolerable_rate = std::pow(2.0, -(bpk - 1.0) / (1.4 + bpk / 50.0));
+    std::cout << "Best possible FP rate %: " << 100.0 * std::pow(2.0, -bpk)
+              << std::endl;
+    std::cout << "Tolerable FP rate %: " << 100.0 * tolerable_rate << std::endl;
+
+    std::cout << "----------------------------" << std::endl;
+    std::cout << "Verifying..." << std::endl;
+
+    uint32_t outside_q_per_f = 1000000 / infos_.size();
+    uint64_t fps = 0;
+    for (uint32_t i = 0; i < infos_.size(); ++i) {
+      FilterInfo &info = infos_[i];
+      for (uint32_t j = 0; j < info.keys_added_; ++j) {
+        ALWAYS_ASSERT(info.reader_->MayMatch(kms_[0].Get(info.filter_id_, j)));
+      }
+      for (uint32_t j = 0; j < outside_q_per_f; ++j) {
+        fps += info.reader_->MayMatch(
+            kms_[0].Get(info.filter_id_, j | 0x80000000));
+      }
+    }
+    std::cout << " No FNs :)" << std::endl;
+    double prelim_rate = double(fps) / outside_q_per_f / infos_.size();
+    std::cout << " Prelim FP rate %: " << (100.0 * prelim_rate) << std::endl;
+
+    if (!FLAGS_allow_bad_fp_rate) {
+      ALWAYS_ASSERT(prelim_rate < tolerable_rate);
+    }
+  }
+
+  std::cout << "----------------------------" << std::endl;
+  std::cout << "Inside queries..." << std::endl;
+  random_.seed(FLAGS_seed + 1);
+  RandomQueryTest(/*inside*/ true, /*dry_run*/ true, kRandomFilter);
+  for (TestMode tm : testModes) {
+    random_.seed(FLAGS_seed + 1);
+    RandomQueryTest(/*inside*/ true, /*dry_run*/ false, tm);
+  }
+
+  std::cout << "----------------------------" << std::endl;
+  std::cout << "Outside queries..." << std::endl;
+  random_.seed(FLAGS_seed + 2);
+  RandomQueryTest(/*inside*/ false, /*dry_run*/ true, kRandomFilter);
+  for (TestMode tm : testModes) {
+    random_.seed(FLAGS_seed + 2);
+    RandomQueryTest(/*inside*/ false, /*dry_run*/ false, tm);
+  }
+
+  std::cout << "----------------------------" << std::endl;
+  std::cout << "Done. (For more info, run with -legend or -help.)" << std::endl;
+}
+
+void FilterBench::RandomQueryTest(bool inside, bool dry_run, TestMode mode) {
+  for (auto &info : infos_) {
+    info.outside_queries_ = 0;
+    info.false_positives_ = 0;
+  }
+
+  uint32_t dry_run_hash = 0;
+  uint64_t max_queries =
+      static_cast<uint64_t>(FLAGS_m_queries * 1000000 + 0.50);
+  // Some filters may be considered secondary in order to implement skewed
+  // queries. num_primary_filters is the number that are to be treated as
+  // equal, and any remainder will be treated as secondary.
+  size_t num_primary_filters = infos_.size();
+  // The proportion (when divided by 2^32 - 1) of filter queries going to
+  // the primary filters (default = all). The remainder of queries are
+  // against secondary filters.
+  uint32_t primary_filter_threshold = 0xffffffff;
+  if (mode == kSingleFilter) {
+    // 100% of queries to 1 filter
+    num_primary_filters = 1;
+  } else if (mode == kFiftyOneFilter) {
+    // 50% of queries
+    primary_filter_threshold /= 2;
+    // to 1% of filters
+    num_primary_filters = (num_primary_filters + 99) / 100;
+  } else if (mode == kEightyTwentyFilter) {
+    // 80% of queries
+    primary_filter_threshold = primary_filter_threshold / 5 * 4;
+    // to 20% of filters
+    num_primary_filters = (num_primary_filters + 4) / 5;
+  }
+  size_t batch_size = 1;
+  std::unique_ptr<Slice *[]> batch_slices;
+  std::unique_ptr<bool[]> batch_results;
+  if (mode == kBatchPrepared || mode == kBatchUnprepared) {
+    batch_size = kms_.size();
+    batch_slices.reset(new Slice *[batch_size]);
+    batch_results.reset(new bool[batch_size]);
+    for (size_t i = 0; i < batch_size; ++i) {
+      batch_slices[i] = &kms_[i].slice_;
+      batch_results[i] = false;
+    }
+  }
+
+  rocksdb::StopWatchNano timer(rocksdb::Env::Default(), true);
+
+  for (uint64_t q = 0; q < max_queries; q += batch_size) {
+    uint32_t filter_index;
+    if (random_() <= primary_filter_threshold) {
+      filter_index = fastrange32(num_primary_filters, random_());
+    } else {
+      // secondary
+      filter_index =
+          num_primary_filters +
+          fastrange32(infos_.size() - num_primary_filters, random_());
+    }
+    FilterInfo &info = infos_[filter_index];
+    for (size_t i = 0; i < batch_size; ++i) {
+      if (inside) {
+        kms_[i].Get(info.filter_id_, fastrange32(info.keys_added_, random_()));
+      } else {
+        kms_[i].Get(info.filter_id_, random_() | 0x80000000);
+        info.outside_queries_++;
+      }
+    }
+    // TODO: implement batched interface to full block reader
+    if (mode == kBatchPrepared && !dry_run && !FLAGS_use_full_block_reader) {
+      for (size_t i = 0; i < batch_size; ++i) {
+        batch_results[i] = false;
+      }
+      info.reader_->MayMatch(batch_size, batch_slices.get(),
+                             batch_results.get());
+      for (size_t i = 0; i < batch_size; ++i) {
+        if (inside) {
+          ALWAYS_ASSERT(batch_results[i]);
+        } else {
+          info.false_positives_ += batch_results[i];
+        }
+      }
+    } else {
+      for (size_t i = 0; i < batch_size; ++i) {
+        if (dry_run) {
+          dry_run_hash ^= rocksdb::BloomHash(kms_[i].slice_);
+        } else {
+          bool may_match;
+          if (FLAGS_use_full_block_reader) {
+            may_match = info.full_block_reader_->KeyMayMatch(
+                kms_[i].slice_,
+                /*prefix_extractor=*/nullptr,
+                /*block_offset=*/rocksdb::kNotValid,
+                /*no_io=*/false, /*const_ikey_ptr=*/nullptr,
+                /*get_context=*/nullptr,
+                /*lookup_context=*/nullptr);
+          } else {
+            may_match = info.reader_->MayMatch(kms_[i].slice_);
+          }
+          if (inside) {
+            ALWAYS_ASSERT(may_match);
+          } else {
+            info.false_positives_ += may_match;
+          }
+        }
+      }
+    }
+  }
+
+  uint64_t elapsed_nanos = timer.ElapsedNanos();
+  double ns = double(elapsed_nanos) / max_queries;
+
+  if (dry_run) {
+    // Printing part of hash prevents dry run components from being optimized
+    // away by compiler
+    std::cout << "  Dry run (" << std::hex << (dry_run_hash & 0xfff) << std::dec
+              << ") ";
+  } else {
+    std::cout << "  " << TestModeToString(mode) << " ";
+  }
+  std::cout << "ns/op: " << ns << std::endl;
+
+  if (!inside && !dry_run && mode == kRandomFilter) {
+    uint64_t q = 0;
+    uint64_t fp = 0;
+    double worst_fp_rate = 0.0;
+    double best_fp_rate = 1.0;
+    for (auto &info : infos_) {
+      q += info.outside_queries_;
+      fp += info.false_positives_;
+      if (info.outside_queries_ > 0) {
+        double fp_rate = double(info.false_positives_) / info.outside_queries_;
+        worst_fp_rate = std::max(worst_fp_rate, fp_rate);
+        best_fp_rate = std::min(best_fp_rate, fp_rate);
+      }
+    }
+    std::cout << "    Average FP rate %: " << 100.0 * fp / q << std::endl;
+    if (!FLAGS_quick) {
+      std::cout << "    Worst   FP rate %: " << 100.0 * worst_fp_rate
+                << std::endl;
+      std::cout << "    Best    FP rate %: " << 100.0 * best_fp_rate
+                << std::endl;
+      std::cout << "    Best possible bits/key: "
+                << -std::log(double(fp) / q) / std::log(2.0) << std::endl;
+    }
+  }
+}
+
+int main(int argc, char **argv) {
+  rocksdb::port::InstallStackTraceHandler();
+  SetUsageMessage(std::string("\nUSAGE:\n") + std::string(argv[0]) +
+                  " [-quick] [OTHER OPTIONS]...");
+  ParseCommandLineFlags(&argc, &argv, true);
+
+  PrintWarnings();
+
+  if (FLAGS_legend) {
+    std::cout
+        << "Legend:" << std::endl
+        << "  \"Inside\" - key that was added to filter" << std::endl
+        << "  \"Outside\" - key that was not added to filter" << std::endl
+        << "  \"FN\" - false negative query (must not happen)" << std::endl
+        << "  \"FP\" - false positive query (OK at low rate)" << std::endl
+        << "  \"Dry run\" - cost of testing and hashing overhead. Consider"
+        << "\n     subtracting this cost from the others." << std::endl
+        << "  \"Single filter\" - essentially minimum cost, assuming filter"
+        << "\n     fits easily in L1 CPU cache." << std::endl
+        << "  \"Batched, prepared\" - several queries at once against a"
+        << "\n     randomly chosen filter, using multi-query interface."
+        << std::endl
+        << "  \"Batched, unprepared\" - similar, but using serial calls"
+        << "\n     to single query interface." << std::endl
+        << "  \"Random filter\" - a filter is chosen at random as target"
+        << "\n     of each query." << std::endl
+        << "  \"Skewed X% in Y%\" - like \"Random filter\" except Y% of"
+        << "\n      the filters are designated as \"hot\" and receive X%"
+        << "\n      of queries." << std::endl;
+  } else {
+    FilterBench b;
+    b.Go();
+  }
+
+  return 0;
+}
+
+#endif  // GFLAGS

util/gflags_compat.h

@@ -10,3 +10,10 @@
 // still google by default.
 #define GFLAGS_NAMESPACE google
 #endif
+
+#ifndef DEFINE_uint32
+// DEFINE_uint32 does not appear in older versions of gflags. This should be
+// a sane definition for those versions.
+#define DEFINE_uint32(name, val, txt) \
+  DEFINE_VARIABLE(GFLAGS_NAMESPACE::uint32, U, name, val, txt)
+#endif