polish conf comment

conf/redis-shake.conf

@@ -82,8 +82,10 @@ filter.key =
 # 指定过滤slot，只让指定的slot通过
 filter.slot =
 
-# big key threshold, the default is 500 * 1024 * 1024. The field of the big key will be split in processing.
+# big key threshold, the default is 500 * 1024 * 1024 bytes. If the value is bigger than
-# 我们对大key有特殊的处理，此处需要指定大key的阈值
+# this given value, all the field will be spilt and write into the target in order.
+# 正常key如果不大，那么都是直接调用restore写入到目的端，如果key对应的value字节超过了给定
+# 的值，那么会分批依次一个一个写入。
 big_key_threshold = 524288000
 
 # use psync command.