When I am writing many files on NFS volume, then a ksoftirq and an rpciod are consuming many CPU.

top - 21:14:54 up 2 days,  9:47,  1 user,  load average: 2.16, 2.22, 2.23
Tasks: 376 total,   3 running, 373 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.1%us,  0.1%sy,  0.0%ni, 87.4%id,  0.0%wa,  0.0%hi, 12.5%si,  0.0%st
Mem:  49454064k total, 42047256k used,  7406808k free,   266396k buffers
Swap: 52428116k total,      388k used, 52427728k free, 40589480k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
   36 root      39  19     0    0    0 R 99.9  0.0   1461:21 ksoftirqd/11
   48 root      39  19     0    0    0 R 95.9  0.0   1245:24 ksoftirqd/15
 5590 root      10  -5     0    0    0 S  4.0  0.0 215:08.52 rpciod/15