Add handy option to turn on direct I/O in db_bench (#1424)

include/rocksdb/options.h

@@ -1106,6 +1106,10 @@ struct DBOptions {
   // Default: false
   bool allow_mmap_writes;
 
+  // Use O_DIRECT for reading file
+  // Default: false
+  bool use_direct_reads;
+
   // If false, fallocate() calls are bypassed
   bool allow_fallocate;
 

tools/db_bench_tool.cc

@@ -761,6 +761,9 @@ DEFINE_bool(mmap_read, rocksdb::EnvOptions().use_mmap_reads,
 DEFINE_bool(mmap_write, rocksdb::EnvOptions().use_mmap_writes,
             "Allow writes to occur via mmap-ing files");
 
+DEFINE_bool(use_direct_reads, rocksdb::EnvOptions().use_direct_reads,
+            "Use O_DIRECT for reading data");
+
 DEFINE_bool(advise_random_on_open, rocksdb::Options().advise_random_on_open,
             "Advise random access on table file open");
 
@@ -2722,6 +2725,9 @@ class Benchmark {
     options.max_background_flushes = FLAGS_max_background_flushes;
     options.compaction_style = FLAGS_compaction_style_e;
     options.compaction_pri = FLAGS_compaction_pri_e;
+    options.allow_mmap_reads = FLAGS_mmap_read;
+    options.allow_mmap_writes = FLAGS_mmap_write;
+    options.use_direct_reads = FLAGS_use_direct_reads;
     if (FLAGS_prefix_size != 0) {
       options.prefix_extractor.reset(
           NewFixedPrefixTransform(FLAGS_prefix_size));

util/db_options.cc

@@ -56,6 +56,7 @@ ImmutableDBOptions::ImmutableDBOptions(const DBOptions& options)
       allow_os_buffer(options.allow_os_buffer),
       allow_mmap_reads(options.allow_mmap_reads),
       allow_mmap_writes(options.allow_mmap_writes),
+      use_direct_reads(options.use_direct_reads),
       allow_fallocate(options.allow_fallocate),
       is_fd_close_on_exec(options.is_fd_close_on_exec),
       stats_dump_period_sec(options.stats_dump_period_sec),
@@ -132,6 +133,8 @@ void ImmutableDBOptions::Dump(Logger* log) const {
          allow_fallocate);
   Header(log, "                      Options.allow_mmap_writes: %d",
          allow_mmap_writes);
+  Header(log, "                       Options.use_direct_reads: %d",
+         use_direct_reads);
   Header(log, "         Options.create_missing_column_families: %d",
          create_missing_column_families);
   Header(log, "                             Options.db_log_dir: %s",

util/db_options.h

@@ -51,6 +51,7 @@ struct ImmutableDBOptions {
   bool allow_os_buffer;
   bool allow_mmap_reads;
   bool allow_mmap_writes;
+  bool use_direct_reads;
   bool allow_fallocate;
   bool is_fd_close_on_exec;
   unsigned int stats_dump_period_sec;

util/env.cc

@@ -316,6 +316,7 @@ void AssignEnvOptions(EnvOptions* env_options, const DBOptions& options) {
   env_options->use_os_buffer = options.allow_os_buffer;
   env_options->use_mmap_reads = options.allow_mmap_reads;
   env_options->use_mmap_writes = options.allow_mmap_writes;
+  env_options->use_direct_reads = options.use_direct_reads;
   env_options->set_fd_cloexec = options.is_fd_close_on_exec;
   env_options->bytes_per_sync = options.bytes_per_sync;
   env_options->compaction_readahead_size = options.compaction_readahead_size;

util/options.cc

@@ -198,6 +198,7 @@ DBOptions::DBOptions()
       allow_os_buffer(true),
       allow_mmap_reads(false),
       allow_mmap_writes(false),
+      use_direct_reads(false),
       allow_fallocate(true),
       is_fd_close_on_exec(true),
       skip_log_error_on_recovery(false),
@@ -267,6 +268,7 @@ DBOptions::DBOptions(const Options& options)
       allow_os_buffer(options.allow_os_buffer),
       allow_mmap_reads(options.allow_mmap_reads),
       allow_mmap_writes(options.allow_mmap_writes),
+      use_direct_reads(options.use_direct_reads),
       allow_fallocate(options.allow_fallocate),
       is_fd_close_on_exec(options.is_fd_close_on_exec),
       skip_log_error_on_recovery(options.skip_log_error_on_recovery),
@@ -333,6 +335,7 @@ void DBOptions::Dump(Logger* log) const {
     Header(log, "      Options.allow_mmap_reads: %d", allow_mmap_reads);
     Header(log, "      Options.allow_fallocate: %d", allow_fallocate);
     Header(log, "     Options.allow_mmap_writes: %d", allow_mmap_writes);
+    Header(log, "      Options.use_direct_reads: %d", use_direct_reads);
     Header(log, "         Options.create_missing_column_families: %d",
         create_missing_column_families);
     Header(log, "                             Options.db_log_dir: %s",

util/options_helper.cc

@@ -74,6 +74,7 @@ DBOptions BuildDBOptions(const ImmutableDBOptions& immutable_db_options,
   options.allow_os_buffer = immutable_db_options.allow_os_buffer;
   options.allow_mmap_reads = immutable_db_options.allow_mmap_reads;
   options.allow_mmap_writes = immutable_db_options.allow_mmap_writes;
+  options.use_direct_reads = immutable_db_options.use_direct_reads;
   options.allow_fallocate = immutable_db_options.allow_fallocate;
   options.is_fd_close_on_exec = immutable_db_options.is_fd_close_on_exec;
   options.stats_dump_period_sec = immutable_db_options.stats_dump_period_sec;

util/options_helper.h

@@ -183,6 +183,9 @@ static std::unordered_map<std::string, OptionTypeInfo> db_options_type_info = {
     {"allow_mmap_writes",
      {offsetof(struct DBOptions, allow_mmap_writes), OptionType::kBoolean,
       OptionVerificationType::kNormal, false, 0}},
+    {"use_direct_reads",
+     {offsetof(struct DBOptions, use_direct_reads), OptionType::kBoolean,
+      OptionVerificationType::kNormal, false, 0}},
     {"allow_2pc",
      {offsetof(struct DBOptions, allow_2pc), OptionType::kBoolean,
       OptionVerificationType::kNormal, false, 0}},

util/options_settable_test.cc

@@ -274,6 +274,7 @@ TEST_F(OptionsSettableTest, DBOptionsAllFieldsSettable) {
                              "stats_dump_period_sec=70127;"
                              "allow_fallocate=true;"
                              "allow_mmap_reads=false;"
+                             "use_direct_reads=false;"
                              "max_log_file_size=4607;"
                              "random_access_max_buffer_size=1048576;"
                              "advise_random_on_open=true;"