performance of RawKvClient.batchPut()

[wuchao-pingcap]

Bug Report

1. Describe the bug

rawKvClient.batchPut(map, ttl);

//tikv-client-java-3.3.0-jh.jar
When map.size()>=1025, rawKvClient.batchPut() will took more then 10 mins. Sometimes timeout will be triggered.
When map.size()=1024, rawKvClient.batchPut() took less then 1 second.
When map.size()=1000, rawKvClient.batchPut() took less then 1 second.

//tikv-client-java-3.1.12.2-jh.jar
When map.size()=2000, rawKvClient.batchPut() took less then 1 second.

2. Minimal reproduce step (Required)

Map<ByteString, ByteString> map = new HashMap<ByteString, ByteString>();
for (int i = 0; i < 1125; i++) {
//map.put(XXX,XXX);
}
rawKvClient.batchPut(map, 0);

3. What did you see instead (Required)

batchPut() failed

4. What did you expect to see? (Required)

batchPut() success

5. What are your Java Client and TiKV versions? (Required)

• Client Java:tikv-client-java-3.3.0-jh.jar
• TiKV:TiKV 6.1、TiKV5.3