diff --git a/db/db_bench.cc b/db/db_bench.cc
index 150ac46664..07b04719ef 100644
--- a/db/db_bench.cc
+++ b/db/db_bench.cc
@@ -79,6 +79,7 @@ DEFINE_string(benchmarks,
               "readtocache,"
               "readreverse,"
               "readwhilewriting,"
+              "readwhilemerging,"
               "readrandomwriterandom,"
               "updaterandom,"
               "randomwithverify,"
@@ -113,6 +114,8 @@ DEFINE_string(benchmarks,
               "of DB\n"
               "\treadwhilewriting      -- 1 writer, N threads doing random "
               "reads\n"
+              "\treadwhilemerging      -- 1 merger, N threads doing random "
+              "reads\n"
               "\treadrandomwriterandom -- N threads doing random-read, "
               "random-write\n"
               "\tprefixscanrandom      -- prefix scan N times in random order\n"
@@ -180,6 +183,10 @@ DEFINE_int32(seek_nexts, 0,
              "How many times to call Next() after Seek() in "
              "fillseekseq and seekrandom");
 
+DEFINE_bool(reverse_iterator, false,
+            "When true use Prev rather than Next for iterators that do "
+            "Seek and then Next");
+
 DEFINE_bool(use_uint64_comparator, false, "use Uint64 user comparator");
 
 DEFINE_int64(batch_size, 1, "Batch size");
@@ -316,8 +323,9 @@ static class std::shared_ptr<rocksdb::Statistics> dbstats;
 DEFINE_int64(writes, -1, "Number of write operations to do. If negative, do"
              " --num reads.");
 
-DEFINE_int32(writes_per_second, 0, "Per-thread rate limit on writes per second."
-             " No limit when <= 0. Only for the readwhilewriting test.");
+DEFINE_int32(writes_per_second, 0, "Per-thread rate limit on writes and merges "
+             "  per second. No limit when <= 0. Only for the readwhilewriting "
+             "  and readwhilemerging tests.");
 
 DEFINE_bool(sync, false, "Sync all writes to disk");
 
@@ -560,6 +568,11 @@ 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");
 
+enum PutOrMerge {
+  kPut,
+  kMerge
+};
+
 enum RepFactory {
   kSkipList,
   kPrefixHash,
@@ -1588,6 +1601,9 @@ class Benchmark {
       } else if (name == Slice("readwhilewriting")) {
         num_threads++;  // Add extra thread for writing
         method = &Benchmark::ReadWhileWriting;
+      } else if (name == Slice("readwhilemerging")) {
+        num_threads++;  // Add extra thread for writing
+        method = &Benchmark::ReadWhileMerging;
       } else if (name == Slice("readrandomwriterandom")) {
         method = &Benchmark::ReadRandomWriteRandom;
       } else if (name == Slice("readrandommergerandom")) {
@@ -2605,7 +2621,7 @@ class Benchmark {
     if (thread->tid > 0) {
       IteratorCreation(thread);
     } else {
-      BGWriter(thread);
+      BGWriter(thread, kPut);
     }
   }
 
@@ -2668,7 +2684,12 @@ class Benchmark {
         Slice value = iter_to_use->value();
         memcpy(value_buffer, value.data(),
                std::min(value.size(), sizeof(value_buffer)));
-        iter_to_use->Next();
+
+        if (!FLAGS_reverse_iterator) {
+          iter_to_use->Next();
+        } else {
+          iter_to_use->Prev();
+        }
         assert(iter_to_use->status().ok());
       }
 
@@ -2692,7 +2713,7 @@ class Benchmark {
     if (thread->tid > 0) {
       SeekRandom(thread);
     } else {
-      BGWriter(thread);
+      BGWriter(thread, kPut);
     }
   }
 
@@ -2733,11 +2754,19 @@ class Benchmark {
     if (thread->tid > 0) {
       ReadRandom(thread);
     } else {
-      BGWriter(thread);
+      BGWriter(thread, kPut);
     }
   }
 
-  void BGWriter(ThreadState* thread) {
+  void ReadWhileMerging(ThreadState* thread) {
+    if (thread->tid > 0) {
+      ReadRandom(thread);
+    } else {
+      BGWriter(thread, kMerge);
+    }
+  }
+
+  void BGWriter(ThreadState* thread, enum PutOrMerge write_merge) {
     // Special thread that keeps writing until other threads are done.
     RandomGenerator gen;
     double last = FLAGS_env->NowMicros();
@@ -2767,9 +2796,16 @@ class Benchmark {
       }
 
       GenerateKeyFromInt(thread->rand.Next() % FLAGS_num, FLAGS_num, &key);
-      Status s = db->Put(write_options_, key, gen.Generate(value_size_));
+      Status s;
+
+      if (write_merge == kPut) {
+          s = db->Put(write_options_, key, gen.Generate(value_size_));
+      } else {
+          s = db->Merge(write_options_, key, gen.Generate(value_size_));
+      }
+
       if (!s.ok()) {
-        fprintf(stderr, "put error: %s\n", s.ToString().c_str());
+        fprintf(stderr, "put or merge error: %s\n", s.ToString().c_str());
         exit(1);
       }
       thread->stats.FinishedOps(&db_, db_.db, 1);
@@ -3207,7 +3243,11 @@ class Benchmark {
       thread->stats.FinishedOps(nullptr, db, 1);
 
       for (int j = 0; j < FLAGS_seek_nexts && i + 1 < FLAGS_num; ++j) {
-        iter->Next();
+        if (!FLAGS_reverse_iterator) {
+          iter->Next();
+        } else {
+          iter->Prev();
+        }
         GenerateKeyFromInt(++i, FLAGS_num, &key);
         assert(iter->Valid() && iter->key() == key);
         thread->stats.FinishedOps(nullptr, db, 1);
diff --git a/tools/benchmark.sh b/tools/benchmark.sh
index f412131e09..07850069ca 100755
--- a/tools/benchmark.sh
+++ b/tools/benchmark.sh
@@ -3,7 +3,7 @@
 
 if [ $# -ne 1 ]; then
   echo -n "./benchmark.sh [bulkload/fillseq/overwrite/filluniquerandom/"
-  echo    "readrandom/readwhilewriting/updaterandom/mergerandom]"
+  echo    "readrandom/readwhilewriting/readwhilemerging/updaterandom/mergerandom]"
   exit 0
 fi
 
@@ -36,7 +36,8 @@ if [ ! -z $DB_BENCH_NO_SYNC ]; then
 fi
 
 num_read_threads=${NUM_READ_THREADS:-16}
-writes_per_second=${WRITES_PER_SEC:-$((80 * K))}  # (only for readwhilewriting)
+# Only for readwhilewriting, readwhilemerging
+writes_per_second=${WRITES_PER_SEC:-$((80 * K))}
 num_nexts_per_seek=${NUM_NEXTS_PER_SEEK:-10}      # (only for rangescanwhilewriting)
 cache_size=$((1 * G))
 duration=${DURATION:-0}
@@ -167,7 +168,7 @@ function run_readrandom {
 }
 
 function run_readwhilewriting {
-  echo "Reading $num_keys random keys from database whiling writing.."
+  echo "Reading $num_keys random keys from database while writing.."
   cmd="./db_bench $params_r --benchmarks=readwhilewriting \
        --use_existing_db=1 \
        --num=$num_keys \
@@ -180,8 +181,23 @@ function run_readwhilewriting {
   eval $cmd
 }
 
+function run_readwhilemerging {
+  echo "Reading $num_keys random keys from database while merging.."
+  cmd="./db_bench $params_r --benchmarks=readwhilemerging \
+       --use_existing_db=1 \
+       --num=$num_keys \
+       --sync=$syncval \
+       --disable_data_sync=0 \
+       --threads=$num_read_threads \
+       --writes_per_second=$writes_per_second \
+       --merge_operator=\"put\" \
+       2>&1 | tee -a $output_dir/benchmark_readwhilemerging.log"
+  echo $cmd | tee $output_dir/benchmark_readwhilemerging.log
+  eval $cmd
+}
+
 function run_rangescanwhilewriting {
-  echo "Range scan $num_keys random keys from database whiling writing.."
+  echo "Range scan $num_keys random keys from database while writing.."
   cmd="./db_bench $params_r --benchmarks=seekrandomwhilewriting \
        --use_existing_db=1 \
        --num=$num_keys \
@@ -249,6 +265,8 @@ for job in ${jobs[@]}; do
     run_readrandom
   elif [ $job = readwhilewriting ]; then
     run_readwhilewriting
+  elif [ $job = readwhilemerging ]; then
+    run_readwhilemerging
   elif [ $job = rangescanwhilewriting ]; then
     run_rangescanwhilewriting
   elif [ $job = updaterandom ]; then
@@ -270,7 +288,7 @@ for job in ${jobs[@]}; do
 
   if [[ $job == readrandom || $job == readwhilewriting \
      || $job == rangescanwhilewriting || $job == updaterandom \
-     || $job == mergerandom ]]; then
+     || $job == mergerandom || $job == readwhilemerging ]]; then
     lat=$(grep "micros\/op" "$output_dir/benchmark_$job.log" \
         | grep "ops\/sec" | awk '{print $3}')
     qps=$(grep "micros\/op" "$output_dir/benchmark_$job.log" \