Re: Ways to Monitor NFS Calls from Client

[David Smith <dsmith at redhat dot com>]

On 08/22/2016 02:40 AM, Lee Eric wrote:
> Hi,
> 
> I'm not sure if this topic had been raised previously. I am exploring
> some ways to monitor NFS calls from client side. So I checked
> https://sourceware.org/systemtap/examples/io/nfs_func_users.stp and
> https://sourceware.org/systemtap/tapsets/nfsd.stp.html. However, that
> makes me confused that because both does not work(or maybe the way I'm
> using is wrong).
>
> For the first one there's no output when client access files on NFS
> server. For the second one I wrote a very small and simple stp:
> 
> probe nfs.proc.open {
>     printf("Opening file %s from server %x\n", filename, server_ip)
> }
> 
> Still, if I access any files there's no output either.
> 
> So I'm curious is there any actual way to capture NFS calls from
> client side via SystemTap? Also, for the second method, any way to get
> other NFS calls like GETATTR, READDIRPLUS etc.?

Systemtap can monitor nfs client and nfs server activity.

The nfsd.stp tapset is for NFS server monitoring. Any script using the
nfsd.stp tapset must be run on the NFS server system. A script using the
nfsd.stp tapset will see NFS activity from all NFS client systems.

The nfs_proc.stp tapset is for NFS client monitoring. Any script using
the nfs_proc.stp tapset must be run on the particular NFS client system.
Note that a script using nfs_proc.stp to do client side NFS monitoring
will only be able to monitor NFS activity on that particular client
system. It won't see any NFS activity from different client systems.

Since you'd like to monitor NFS calls from a NFS client, you'd want to
use the nfs_proc.stp tapset. Here's an example run from one of my
systems that is an NFS client. In the following example, the file
'ChangeLog' is stored on an NFS partition:

====
# stap -e 'probe nfs.proc.open { printf("%s(%s)\n", name, argstr) }' -c
'cat ChangeLog > /dev/null'
nfs.proc.open(ChangeLog,32768,32797)
====

If something similar doesn't work for you, we'll have to dig deeper into
your setup.

As far as GETATTR and READDIRPLUS goes, it appears that the nfs_proc.stp
tapset doesn't have probes for those calls. However, it would be fairly
easy to add your own.

-- 
David Smith
dsmith@redhat.com
Red Hat
http://www.redhat.com
256.217.0141 (direct)
256.837.0057 (fax)