hbase的client和server部署在同一台机子，查询响应慢的问题。

主要修改了server端的tcpnodelay为false，就解决这个问题了。

tcpnodelay为false时的tcpdump为(有40ms的延迟)

16:17:00.576582 IP linux-idy0.48538 > linux-idy0.60020: P 5434:5643(209) ack 247472 win 387 <nop,nop,timestamp 567208394 567208393>

16:17:00.576869 IP linux-idy0.60020 > linux-idy0.48538: P 247472:255664(8192) ack 5643 win 6149 <nop,nop,timestamp 567208394 567208394>

16:17:00.616084 IP linux-idy0.48538 > linux-idy0.60020: . ack 255664 win 387 <nop,nop,timestamp 567208404 567208394>

16:17:00.616105 IP linux-idy0.60020 > linux-idy0.48538: P 255664:256941(1277) ack 5643 win 6149 <nop,nop,timestamp 567208404 567208404>

16:17:00.616199 IP linux-idy0.48538 > linux-idy0.60020: . ack 256941 win 387 <nop,nop,timestamp 567208404 567208404>

 

tcpnodelay为true时的tcpdump为

11:18:05.513811 IP linux-idy0.12741 > linux-idy0.60020: P 31350:31559(209) ack 1420351 win 2314 <nop,nop,timestamp 562724628 562724627>

11:18:05.514037 IP linux-idy0.60020 > linux-idy0.12741: P 1420351:1428543(8192) ack 31559 win 6145 <nop,nop,timestamp 562724628 562724628>

11:18:05.514067 IP linux-idy0.60020 > linux-idy0.12741: P 1428543:1429820(1277) ack 31559 win 6145 <nop,nop,timestamp 562724628 562724628>

11:18:05.514137 IP linux-idy0.12741 > linux-idy0.60020: . ack 1429820 win 2303 <nop,nop,timestamp 562724628 562724628>

 

连接别的hbase的server时的tcpdump为（tcpnodelay为false）

11:28:46.280278 IP linux-idy0.60201 > linux-kl9e.60020: P 28006:28215(209) ack 1268847 win 1437 <nop,nop,timestamp 562884820 562802550>

11:28:46.280634 IP linux-kl9e.60020 > linux-idy0.60201: P 1268847:1277039(8192) ack 28215 win 3077 <nop,nop,timestamp 562802551 562884820>

11:28:46.280647 IP linux-idy0.60201 > linux-kl9e.60020: . ack 1277039 win 1437 <nop,nop,timestamp 562884820 562802551>

11:28:46.280740 IP linux-kl9e.60020 > linux-idy0.60201: P 1277039:1278316(1277) ack 28215 win 3077 <nop,nop,timestamp 562802551 562884820>

 

可以看出当使用本机的loopback时，有ack延迟的问题。但通过eth0连接别的机子却没有这个问题，比较费解。

使用了ethtool -K lo gro on/off开关合并ACK，也没有用。

参考:

http://www.iteye.com/topic/1110883

http://blog.csdn.net/historyasamirror/article/details/6423235

http://blog.csdn.net/wjtxt/article/details/6606022

http://www.cnblogs.com/yxfqust/archive/2006/07/28/461836.html

http://blog.163.com/xychenbaihu@yeah/blog/static/132229655201231214038740/

 

可能是因为lo和eth0的MT值不同而引起的，参考

http://blog.sina.com.cn/s/blog_5ef988640100de93.html