added more details on the line chart of the rw-benchmark

Signed-off-by: Benjamin Wang <[email protected]>

tools/rw-benchmark/README.md

@@ -15,7 +15,7 @@ To get a mixed read/write performance evaluation result:
 Note: the result csv file will be saved to current working directory. The working directory is where etcd database is saved. The working directory is designed for scenarios where a different mounted disk is preferred.
 
 ### Plot Graphs
-To generate a HTML page (read and write) based on the benchmark result csv file:
+To generate a HTML page including all the line charts based on the benchmark result csv files:
 ```sh
 # To generate a HTML page with each chart including one pair of read & write
 # benchmark results from one data csv file.
@@ -25,3 +25,7 @@ To generate a HTML page (read and write) based on the benchmark result csv file:
 # benchmark results from two data csv files respectively.
 ./rw-benchmark -l "main:dev" ${FIRST_CSV_FILE} ${SECOND_CSV_FILE}
 ```
+
+The read QPS is displayed as <span style="color:blue">blue</span>, and write QPS is displayed as <span style="color:red">red</span>. 
+The data in the second CSV file is rendered as dashed line if present. See example in [example/rw_benchmark.html](example/rw_benchmark.html).
+Note each line in the line chart can be hidden or displayed by clicking on the related legend.