db_bench periodically dump stats to info log (#4109)

Summary:
give control of how often stats are printed, including jemalloc stats if enabled. Previously the default was 10 minutes so we'd only see updated stats for very long benchmark runs.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4109

Differential Revision: D8796444

Pulled By: ajkr

fbshipit-source-id: fd7902fe3f105fae89322c4ab63316bba4a2b15e

tools/db_bench_tool.cc

@@ -1028,6 +1028,8 @@ DEFINE_bool(identity_as_first_hash, false, "the first hash function of cuckoo "
             "table becomes an identity function. This is only valid when key "
             "is 8 bytes");
 DEFINE_bool(dump_malloc_stats, true, "Dump malloc stats in LOG ");
+DEFINE_uint32(stats_dump_period_sec, rocksdb::Options().stats_dump_period_sec,
+              "Gap between printing stats to log in seconds");
 
 enum RepFactory {
   kSkipList,
@@ -3367,6 +3369,7 @@ void VerifyDBFromDB(std::string& truth_db_name) {
     options.wal_dir = FLAGS_wal_dir;
     options.create_if_missing = !FLAGS_use_existing_db;
     options.dump_malloc_stats = FLAGS_dump_malloc_stats;
+    options.stats_dump_period_sec = FLAGS_stats_dump_period_sec;
 
     options.compression_opts.level = FLAGS_compression_level;
     options.compression_opts.max_dict_bytes = FLAGS_compression_max_dict_bytes;