NFSD high CPU usage

[Rick Romero]

  Quoting Adam Guimont <aguimont at tezzaron.com>:

> Rick Romero wrote:
>> Does your ZFS pool have log devices?
>> How does gstat -d   look?
>>
>> If the drives are busy, try adding
>> vfs.nfsd.async: 0
>
> No log devices but the disks are not busy when this happens.
>
> I have an atop snapshot from the last time it happened:
> http://pastebin.com/raw.php?i=LQjbKTXR

Are the disks busy before it happens?   I'm far from an expert, but when
running ZFS with NFS, I've had a lot of issues.  My final resolutions were
to turn ASYNC off and have log devices and I even have SSD volumes now.
Otherwise under load the NFS server gets hung up. It never seemed to happen
on UFS, but due to the number of small files I have, ZFS provides the best
backup functionality. I'm now trying to move all functions from NFS (to
more TCP client/server).

You have different info than I've gathered, and it might be because of
usage. I actively use the system that I've seen NFS dump on, so I see the
slowness beginning. Once NFS dies, the drive load goes back to normal. I
wonder, if maybe you are just managing a system for others, and you don't
see it until after the fact?  Just a thought based on my limited
experience.

Rick