[Beowulf] max number of NFS threads: NFS config optimization

[David N. Lombard]

On Thu, Dec 18, 2008 at 12:59:06PM -0700, Rahul Nabar wrote:
> For a while I've been seeing errors of this sort in my /var/log/messages
> 
> kernel: nfsd: too many open TCP sockets, consider increasing the number of
> nfsd threads
> 
> I googled a bunch and think the solution might be to boost RPCNFSDCOUNT in
> the line "[ -z "$RPCNFSDCOUNT" ] && RPCNFSDCOUNT=8"  in the file
> /etc/init.d/nfs.
> 
> Question: This seems a suspicious place to change it. Isn't there a nfs
> config file somewhere else?

That would be a Bad Thing(TM).  That line is looking to see if the shell
variable RPCNFSDCOUNT has a value set; if not, it sets a default value
of 8.

Look up in the file.  In my system (Fedora 7), this line is earlier in
the file

	[ -f /etc/sysconfig/nfs ] && . /etc/sysconfig/nfs

This line looks for the file /etc/sysconfig/nfs and sources it. So,
you would put a line that looks like

	RPCNFSDCOUNT=16

if you wanted to set the value to 16.

> Question2: How high can I boost the number of NFS threads? Or how I should
> I? Is there any metric I can track to decide an optimum number? Most
> recomendations were for 32, 64 or 128. What do people suggest? Any
> downsides to having numbers that are too high?

How many concurrent requests do you think you'll need to satisfy?
Try that number.

-- 
David N. Lombard, Intel, Irvine, CA
I do not speak for Intel Corporation; all comments are strictly my own.