nfs client issue at netbsd-8

[6bone%6bone.informatik.uni-leipzig.de@localhost]

Hello,

I have problems with the nfs-client under netbsd-8. In principle, the nfs 
works. Some time after an nfs share is mounted, there are network breaks 
on the client. The following ping from the outside on the client shows the 
phenomenon.


...
64 bytes from 139.18.xx.yy: icmp_seq=6496 ttl=254 time=0.175 ms
64 bytes from 139.18.xx.yy: icmp_seq=6497 ttl=254 time=0.178 ms
64 bytes from 139.18.xx.yy: icmp_seq=6498 ttl=254 time=0.202 ms
64 bytes from 139.18.xx.yy: icmp_seq=6499 ttl=254 time=0.179 ms
64 bytes from 139.18.xx.yy: icmp_seq=6500 ttl=254 time=0.161 ms
64 bytes from 139.18.xx.yy: icmp_seq=6501 ttl=254 time=3126 ms
64 bytes from 139.18.xx.yy: icmp_seq=6502 ttl=254 time=2126 ms
64 bytes from 139.18.xx.yy: icmp_seq=6503 ttl=254 time=1126 ms
64 bytes from 139.18.xx.yy: icmp_seq=6504 ttl=254 time=126 ms
64 bytes from 139.18.xx.yy: icmp_seq=6505 ttl=254 time=0.177 ms
64 bytes from 139.18.xx.yy: icmp_seq=6506 ttl=254 time=0.182 ms
64 bytes from 139.18.xx.yy: icmp_seq=6507 ttl=254 time=0.098 ms
...

At the time of ping, no user process is running on the nfs client. There 
is no disk or network access. The behavior is repeated within a few 
minutes. Within a few days, the intervals of occurrence will be shorter. 
Over time, the CPU usage of the system process continues to increase. See the 
following top.

load averages:  0.00,  0.01,  0.00;               up 12+10:41:47 
35 processes: 1 runnable, 32 sleeping, 2 on CPU
CPU0 states:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
CPU1 states:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
CPU2 states:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
CPU3 states:  0.0% user,  0.0% nice,  0.0% system,  0.0% interrupt,  100% idle
Memory: 3697M Act, 308K Inact, 11M Wired, 36M Exec, 3584M File, 35G Free
Swap: 59G Total, 59G Free

  PID USERNAME PRI NICE   SIZE   RES STATE      TIME   WCPU    CPU COMMAND
    0 root       0    0     0K  708M CPU/3     62:17  0.00% 65.89% [system]
  975 root      85    0    48M 2456K kqueue/0   0:33  0.00%  0.00% master
  191 root      85    0    23M 2068K kqueue/1   0:16  0.00%  0.00% syslogd
  364 root      85    0    23M   10M pause/2    0:03  0.00%  0.00% ntpd
  964 postfix   85    0    49M 3880K kqueue/1   0:03  0.00%  0.00% qmgr

After umounting the nfs-share the problems disappear. A reboot is not 
necessary.

The nfs server is a netapp. The nfs share has a size of 10TB (usage 5.7TB, 
3600307 files, 92262 directories).

The mount-options are: 
userquota,nosuid,rw,tcp,soft,intr,-x15,rdirplus,rsize=65536,-I65536,readahead=4

Are there any ideas which mount option can be the problem? Is it possible 
to eliminate the problem with a configuration change or is it a bug?

Thank you for your efforts

Best Regards
Uwe