option to print malloc stats at the end of db_bench (#4582)

Summary:
Option to print malloc stats to stdout at the end of db_bench. This is different from `--dump_malloc_stats`, which periodically print the same information to LOG file.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4582

Differential Revision: D10520814

Pulled By: yiwu-arbug

fbshipit-source-id: beff5e514e414079d31092b630813f82939ffe5c

tools/db_bench_tool.cc

@@ -33,10 +33,12 @@
 #include <unordered_map>
 
 #include "db/db_impl.h"
+#include "db/malloc_stats.h"
 #include "db/version_set.h"
 #include "hdfs/env_hdfs.h"
 #include "monitoring/histogram.h"
 #include "monitoring/statistics.h"
+#include "options/cf_options.h"
 #include "port/port.h"
 #include "port/stack_trace.h"
 #include "rocksdb/cache.h"
@@ -45,7 +47,6 @@
 #include "rocksdb/filter_policy.h"
 #include "rocksdb/memtablerep.h"
 #include "rocksdb/options.h"
-#include "options/cf_options.h"
 #include "rocksdb/perf_context.h"
 #include "rocksdb/persistent_cache.h"
 #include "rocksdb/rate_limiter.h"
@@ -1038,6 +1039,9 @@ DEFINE_bool(dump_malloc_stats, true, "Dump malloc stats in LOG ");
 DEFINE_uint64(stats_dump_period_sec, rocksdb::Options().stats_dump_period_sec,
               "Gap between printing stats to log in seconds");
 
+DEFINE_bool(print_malloc_stats, false,
+            "Print malloc stats to stdout after benchmarks finish.");
+
 enum RepFactory {
   kSkipList,
   kPrefixHash,
@@ -5804,6 +5808,13 @@ int db_bench_tool(int argc, char** argv) {
 
   rocksdb::Benchmark benchmark;
   benchmark.Run();
+
+  if (FLAGS_print_malloc_stats) {
+    std::string stats_string;
+    rocksdb::DumpMallocStats(&stats_string);
+    fprintf(stdout, "Malloc stats:\n%s\n", stats_string.c_str());
+  }
+
   return 0;
 }
 }  // namespace rocksdb