Re: more problems with NFS. sort of repeatable problem with vmplayer

["NeilBrown" <neilb@suse.de>]

On Wed, 06 Oct 2021, Charles Hedrick wrote:

> 
> It tried running vmplayer.  Shortly after starting to create a new VM,
> vmplayer hung.  I had another window with a shell.  I went into the
> directory with the vm files and did “ls -ltrc”.  It didn’t quite hang,
> but look about a minute to finish I also saw log entries from VMware
> complaining that disk operations took several seconds. 

Useful information to provide when a process appears to hang on NFS
include:

- cat /proc/$PID/stack

- rpcdebug -m nfs -s all; rpcdebug -m rpc -s all ; sleep 2 ; 
   rpcdebug -m rpc -c all; rpcdebug -m nfs -c all
 then collect kernel logs

- tcpdump -w filename.pcap -s 0 -c 1000 port 2049
  and compress filename.pcap and put it somewhere we can find it.

- trace-cmd record -e 'nfs:*' sleep 2
  trace-cmd report > filename

> 
> We’re probably an unusual installation.  We’re a CS department, with
> researchers and also a large time-sharing environment for students
> (spread across many machines, with a graphical interface using Xrdb,
> etc).  Our people use every piece of software under the sun. 

Probably not all that unusual.  There certainly are lots of large and
varied NFS sites out there.

> 
> Client and server are both Ubuntu 20.04. Server is on ZFS with NVMe storage.

If it is possible to reproduce without ZFS, that would provide useful
information.
I don't think it is *likely* that ZFS causes the problem, but neither
would I be surprised if it did.

NeilBrown