diff --git a/db/db_bench.cc b/db/db_bench.cc
index 096b183772..1bc1caa73a 100644
--- a/db/db_bench.cc
+++ b/db/db_bench.cc
@@ -13,6 +13,7 @@
 #include "rocksdb/cache.h"
 #include "rocksdb/db.h"
 #include "rocksdb/env.h"
+#include "rocksdb/memtablerep.h"
 #include "rocksdb/write_batch.h"
 #include "rocksdb/statistics.h"
 #include "port/port.h"
@@ -79,6 +80,7 @@ static const char* FLAGS_benchmarks =
     "snappycomp,"
     "snappyuncomp,"
     "acquireload,"
+    "fillfromstdin,"
     ;
 // the maximum size of key in bytes
 static const int MAX_KEY_SIZE = 128;
@@ -906,6 +908,9 @@ class Benchmark {
       } else if (name == Slice("fillrandom")) {
         fresh_db = true;
         method = &Benchmark::WriteRandom;
+      } else if (name == Slice("fillfromstdin")) {
+        fresh_db = true;
+        method = &Benchmark::WriteFromStdin;
       } else if (name == Slice("filluniquerandom")) {
         fresh_db = true;
         if (num_threads > 1) {
@@ -1342,6 +1347,54 @@ class Benchmark {
     DoWrite(thread, UNIQUE_RANDOM);
   }
 
+  void writeOrFail(WriteBatch& batch) {
+    Status s = db_->Write(write_options_, &batch);
+    if (!s.ok()) {
+      fprintf(stderr, "put error: %s\n", s.ToString().c_str());
+      exit(1);
+    }
+  }
+
+  void WriteFromStdin(ThreadState* thread) {
+    size_t count = 0;
+    WriteBatch batch;
+    const size_t bufferLen = 32 << 20;
+    unique_ptr<char[]> line = unique_ptr<char[]>(new char[bufferLen]);
+    char* linep = line.get();
+    const int batchSize = 100 << 10;
+    const char columnSeparator = '\t';
+    const char lineSeparator = '\n';
+
+    while (fgets(linep, bufferLen, stdin) != nullptr) {
+      ++count;
+      char* tab = std::find(linep, linep + bufferLen, columnSeparator);
+      if (tab == linep + bufferLen) {
+        fprintf(stderr, "[Error] No Key delimiter TAB at line %ld\n", count);
+        continue;
+      }
+      Slice key(linep, tab - linep);
+      tab++;
+      char* endLine = std::find(tab, linep + bufferLen, lineSeparator);
+      if (endLine  == linep + bufferLen) {
+        fprintf(stderr, "[Error] No ENTER at end of line # %ld\n", count);
+        continue;
+      }
+      Slice value(tab, endLine - tab);
+      thread->stats.FinishedSingleOp(db_);
+      thread->stats.AddBytes(endLine - linep - 1);
+
+      if (batch.Count() < batchSize) {
+        batch.Put(key, value);
+        continue;
+      }
+      writeOrFail(batch);
+      batch.Clear();
+    }
+    if (batch.Count() > 0) {
+      writeOrFail(batch);
+    }
+  }
+
   void DoWrite(ThreadState* thread, WriteMode write_mode) {
     const int test_duration = write_mode == RANDOM ? FLAGS_duration : 0;
     const int num_ops = writes_ == 0 ? num_ : writes_ ;
@@ -2320,8 +2373,8 @@ int main(int argc, char** argv) {
       } else {
         FLAGS_key_size = n;
       }
-    } else if (sscanf(argv[i], "--write_buffer_size=%d%c", &n, &junk) == 1) {
-      FLAGS_write_buffer_size = n;
+    } else if (sscanf(argv[i], "--write_buffer_size=%lld%c", &ll, &junk) == 1) {
+      FLAGS_write_buffer_size = ll;
     } else if (sscanf(argv[i], "--max_write_buffer_number=%d%c", &n, &junk) == 1) {
       FLAGS_max_write_buffer_number = n;
     } else if (sscanf(argv[i], "--min_write_buffer_number_to_merge=%d%c",
diff --git a/util/vectorrep.cc b/util/vectorrep.cc
index 14443c7314..8770f60b98 100644
--- a/util/vectorrep.cc
+++ b/util/vectorrep.cc
@@ -36,11 +36,15 @@ class VectorRep : public MemTableRep {
   virtual ~VectorRep() override { }
 
   class Iterator : public MemTableRep::Iterator {
+    class VectorRep* vrep_;
     std::shared_ptr<std::vector<const char*>> bucket_;
-    typename std::vector<const char*>::const_iterator cit_;
+    typename std::vector<const char*>::const_iterator mutable cit_;
     const KeyComparator& compare_;
+    bool mutable sorted_;
+    void DoSort() const;
    public:
-    explicit Iterator(std::shared_ptr<std::vector<const char*>> bucket,
+    explicit Iterator(class VectorRep* vrep,
+      std::shared_ptr<std::vector<const char*>> bucket,
       const KeyComparator& compare);
 
     // Initialize an iterator over the specified collection.
@@ -82,11 +86,12 @@ class VectorRep : public MemTableRep {
   virtual std::shared_ptr<MemTableRep::Iterator> GetIterator() override;
 
  private:
+  friend class Iterator;
   typedef std::vector<const char*> Bucket;
   std::shared_ptr<Bucket> bucket_;
   mutable port::RWMutex rwlock_;
-  bool immutable_ = false;
-  bool sorted_ = false;
+  bool immutable_;
+  bool sorted_;
   const KeyComparator& compare_;
 };
 
@@ -119,16 +124,42 @@ size_t VectorRep::ApproximateMemoryUsage() {
 
 VectorRep::VectorRep(const KeyComparator& compare, Arena* arena, size_t count)
   : bucket_(new Bucket(count)),
+    immutable_(false),
+    sorted_(false),
     compare_(compare) { }
 
-VectorRep::Iterator::Iterator(std::shared_ptr<std::vector<const char*>> bucket,
+VectorRep::Iterator::Iterator(class VectorRep* vrep,
+                   std::shared_ptr<std::vector<const char*>> bucket,
                    const KeyComparator& compare)
-: bucket_(bucket),
-  cit_(bucket_->begin()),
-  compare_(compare) { }
+: vrep_(vrep),
+  bucket_(bucket),
+  cit_(nullptr),
+  compare_(compare),
+  sorted_(false) { }
+
+void VectorRep::Iterator::DoSort() const {
+  // vrep is non-null means that we are working on an immutable memtable
+  if (!sorted_ && vrep_ != nullptr) {
+    WriteLock l(&vrep_->rwlock_);
+    if (!vrep_->sorted_) {
+      std::sort(bucket_->begin(), bucket_->end(), Compare(compare_));
+      cit_ = bucket_->begin();
+      vrep_->sorted_ = true;
+    }
+    sorted_ = true;
+  }
+  if (!sorted_) {
+    std::sort(bucket_->begin(), bucket_->end(), Compare(compare_));
+    cit_ = bucket_->begin();
+    sorted_ = true;
+  }
+  assert(sorted_);
+  assert(vrep_ == nullptr || vrep_->sorted_);
+}
 
 // Returns true iff the iterator is positioned at a valid node.
 bool VectorRep::Iterator::Valid() const {
+  DoSort();
   return cit_ != bucket_->end();
 }
 
@@ -165,6 +196,7 @@ void VectorRep::Iterator::Prev() {
 
 // Advance to the first entry with a key >= target
 void VectorRep::Iterator::Seek(const char* target) {
+  DoSort();
   // Do binary search to find first value not less than the target
   cit_ = std::equal_range(bucket_->begin(),
                           bucket_->end(),
@@ -177,12 +209,14 @@ void VectorRep::Iterator::Seek(const char* target) {
 // Position at the first entry in collection.
 // Final state of iterator is Valid() iff collection is not empty.
 void VectorRep::Iterator::SeekToFirst() {
+  DoSort();
   cit_ = bucket_->begin();
 }
 
 // Position at the last entry in collection.
 // Final state of iterator is Valid() iff collection is not empty.
 void VectorRep::Iterator::SeekToLast() {
+  DoSort();
   cit_ = bucket_->end();
   if (bucket_->size() != 0) {
     --cit_;
@@ -190,21 +224,16 @@ void VectorRep::Iterator::SeekToLast() {
 }
 
 std::shared_ptr<MemTableRep::Iterator> VectorRep::GetIterator() {
-  std::shared_ptr<Bucket> tmp;
   ReadLock l(&rwlock_);
+  // Do not sort here. The sorting would be done the first time
+  // a Seek is performed on the iterator.
   if (immutable_) {
-    rwlock_.Unlock();
-    rwlock_.WriteLock();
-    tmp = bucket_;
-    if (!sorted_) {
-      std::sort(tmp->begin(), tmp->end(), Compare(compare_));
-      sorted_ = true;
-    }
+    return std::make_shared<Iterator>(this, bucket_, compare_);
   } else {
+    std::shared_ptr<Bucket> tmp;
     tmp.reset(new Bucket(*bucket_)); // make a copy
-    std::sort(tmp->begin(), tmp->end(), Compare(compare_));
+    return std::make_shared<Iterator>(nullptr, tmp, compare_);
   }
-  return std::make_shared<Iterator>(tmp, compare_);
 }
 } // anon namespace