!10948 modify maskrcnn readme，add description of bs and hard disk

From: @yuzhenhua666
Reviewed-by: @oacjiewen,@wuxuejian
Signed-off-by: @wuxuejian

model_zoo/official/cv/maskrcnn/README.md

@@ -505,6 +505,7 @@ python export.py --ckpt_file [CKPT_PATH] --device_target [DEVICE_TARGET] --file_
 ### Usage
 
 Before performing inference, the air file must bu exported by export script on the 910 environment.
+Current batch_ Size can only be set to 1. The inference process needs about 600G hard disk space to save the reasoning results.
 
 ```shell
 # Ascend310 inference

model_zoo/official/cv/maskrcnn/README_CN.md

@@ -439,7 +439,7 @@ python export.py --ckpt_file [CKPT_PATH] --device_target [DEVICE_TARGET] --file_
 
 ### 使用方法
 
-在推理之前需要在昇腾910环境上完成模型的导出。
+在推理之前需要在昇腾910环境上完成模型的导出。目前推理只支持batch_size=1。推理过程需要占用大约600G的硬盘空间来保存推理的结果。
 
 ```shell
 # Ascend310 推理