rsync 同步文件时卡住不动

具体表现是：我使用rsync往服务器同步文件，我设置了超时timeout=5（不设置这个值也会出现这样的问题），然后运行大约1小时后，不断出现timeout的错误提示，出现大约10多个后，程序卡在rsync上不往下运行。此时的CPU很高，如下：

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
2243 luffyctz 25 0 3900 1184 944 R 99 0.0 8:08.98 rsync
请问这是什么问题呢？

server端的log补充：
2015/03/24 20:05:59 [9603] Service registration expired, refreshing it
2015/03/24 20:05:59 [9603] rsyncd registering 1 service with slpd for 300 seconds:
2015/03/24 20:05:59 [9603] Could not resolve hostname: Name or service not known
2015/03/24 20:10:36 [23380] rsync error: timeout in data send/receive (code 30) at io.c(171) [receiver=2.6.8]

客户端的错误提示：
rsync error: timeout in data send/receive (code 30) at io.c(171) [receiver=2.6.8]
rsync: connection unexpectedly closed (4 bytes received so far) [sender]