Blob DB: db_bench flag to control BlobDB's garbage collection

Summary:
flag: blob_db_enable_gc, to control BlobDb's enable_garbage_collection.
Closes https://github.com/facebook/rocksdb/pull/3190

Differential Revision: D6383395

Pulled By: sagar0

fbshipit-source-id: 4134e835150748c425b8187264273a54c6d8381c

tools/db_bench_tool.cc

@@ -618,14 +618,11 @@ DEFINE_bool(expand_range_tombstones, false,
             "Expand range tombstone into sequential regular tombstones.");
 
 #ifndef ROCKSDB_LITE
+// Transactions Options
 DEFINE_bool(optimistic_transaction_db, false,
             "Open a OptimisticTransactionDB instance. "
             "Required for randomtransaction benchmark.");
 
-DEFINE_bool(use_blob_db, false,
-            "Open a BlobDB instance. "
-            "Required for largevalue benchmark.");
-
 DEFINE_bool(transaction_db, false,
             "Open a TransactionDB instance. "
             "Required for randomtransaction benchmark.");
@@ -661,11 +658,22 @@ DEFINE_string(
     "\t--dump_malloc_stats\n"
     "\t--num_multi_db\n");
 
+// FIFO Compaction Options
 DEFINE_uint64(fifo_compaction_max_table_files_size_mb, 0,
               "The limit of total table file sizes to trigger FIFO compaction");
+
 DEFINE_bool(fifo_compaction_allow_compaction, true,
             "Allow compaction in FIFO compaction.");
+
 DEFINE_uint64(fifo_compaction_ttl, 0, "TTL for the SST Files in seconds.");
+
+// Blob DB Options
+DEFINE_bool(use_blob_db, false,
+            "Open a BlobDB instance. "
+            "Required for largevalue benchmark.");
+
+DEFINE_bool(blob_db_enable_gc, false,
+            "Enable BlobDB garbage collection");
 #endif  // ROCKSDB_LITE
 
 DEFINE_bool(report_bg_io_stats, false,
@@ -3382,6 +3390,7 @@ void VerifyDBFromDB(std::string& truth_db_name) {
       }
     } else if (FLAGS_use_blob_db) {
       blob_db::BlobDBOptions blob_db_options;
+      blob_db_options.enable_garbage_collection = FLAGS_blob_db_enable_gc;
       blob_db::BlobDB* ptr = nullptr;
       s = blob_db::BlobDB::Open(options, blob_db_options, db_name, &ptr);
       if (s.ok()) {