Add histogram for value size per operation

db/db_impl.cc

@@ -3327,6 +3327,7 @@ Status DBImpl::GetImpl(const ReadOptions& read_options,
 
     RecordTick(stats_, NUMBER_KEYS_READ);
     RecordTick(stats_, BYTES_READ, value->size());
+    MeasureTime(stats_, BYTES_PER_READ, value->size());
   }
   return s;
 }
@@ -3437,6 +3438,7 @@ std::vector<Status> DBImpl::MultiGet(
   RecordTick(stats_, NUMBER_MULTIGET_CALLS);
   RecordTick(stats_, NUMBER_MULTIGET_KEYS_READ, num_keys);
   RecordTick(stats_, NUMBER_MULTIGET_BYTES_READ, bytes_read);
+  MeasureTime(stats_, BYTES_PER_MULTIGET, bytes_read);
   PERF_TIMER_STOP(get_post_process_time);
 
   return stat_list;
@@ -4321,6 +4323,7 @@ Status DBImpl::WriteImpl(const WriteOptions& write_options,
     // Record statistics
     RecordTick(stats_, NUMBER_KEYS_WRITTEN, total_count);
     RecordTick(stats_, BYTES_WRITTEN, total_byte_size);
+    MeasureTime(stats_, BYTES_PER_WRITE, total_byte_size);
     PERF_TIMER_STOP(write_pre_and_post_process_time);
 
     if (write_options.disableWAL) {

include/rocksdb/statistics.h

@@ -280,6 +280,10 @@ enum Histograms : uint32_t {
   SST_READ_MICROS,
   // The number of subcompactions actually scheduled during a compaction
   NUM_SUBCOMPACTIONS_SCHEDULED,
+  // Value size distribution in each operation
+  BYTES_PER_READ,
+  BYTES_PER_WRITE,
+  BYTES_PER_MULTIGET,
   HISTOGRAM_ENUM_MAX,  // TODO(ldemailly): enforce HistogramsNameMap match
 };
 
@@ -307,6 +311,9 @@ const std::vector<std::pair<Histograms, std::string>> HistogramsNameMap = {
     {WRITE_STALL, "rocksdb.db.write.stall"},
     {SST_READ_MICROS, "rocksdb.sst.read.micros"},
     {NUM_SUBCOMPACTIONS_SCHEDULED, "rocksdb.num.subcompactions.scheduled"},
+    {BYTES_PER_READ, "rocksdb.bytes.per.read"},
+    {BYTES_PER_WRITE, "rocksdb.bytes.per.write"},
+    {BYTES_PER_MULTIGET, "rocksdb.bytes.per.multiget"},
 };
 
 struct HistogramData {