From: Brad Barnett <lists@L8R.net>
Subject: Re: knfsd brought to its knees, by a simple rsync or cp
 operation
Date: Mon, 28 Feb 2005 11:20:18 -0500
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Cc: nfs@lists.sourceforge.net
To: Olaf Kirch <okir@suse.de>
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On Mon, 28 Feb 2005 16:44:55 +0100
Olaf Kirch <okir@suse.de> wrote:

> On Mon, Feb 28, 2005 at 10:23:07AM -0500, Brad Barnett wrote:
> > During my tests involving "ls", no one else was accessing the server. 
> > I have noatime set for both client and server mounts.. just in case.
> > 
> > So, there should be no writes for knfsd to do.  There was only one
> > read operation, and that was a "ls -R /nfsmount".
> 
> Well, you were talking about rsync and cp, so it's either reads or
> writes going over the wire, or both.

The rsync or cp operation are on the server.

> 
> > >  -	by tying up all knfsd threads on the server. Try to bump the
> > >  	number of nfsd processes
> > > 
> > >  -	by tying up all RPC slots on the client. Make sure your wsize
> > >  	isn't too big (8k is reasonable)
> > 
> > There is only one client (during my tests), so #1 can't be the case. 
> 
> One NFS client can issue many requests simultaenously, thereby tying
> up more than one nfsd thread.

Yes, but the only activity is a single "ls" on the client.. I don't think
this would use more than one thread.

> 
> > This is what I don't understand.  Why is one single 'ls' on a single
> > client, the only nfs client, brought to a standstill by a single cp or
> > rsync?  It's very weird, and it does not seem to be because of write
> > operations the client is performing.
> 
> Where do these cp and rsync calls occur? From your first message I
> assumed they were on the client, operating on the NFS mounted file
> system.
> 

The cp or rsync are occurring locally on the server.  

Eg

One client has an nfs mount.  It issues an "ls".  The response is instant,
without slowdowns.

I start a long and extensive cp -a process on the nfs server.  Local 'ls'
responses are instant.  Write and read operations are instant (it's a raid
10) on the local box, as well.  However, my single remote client's "ls"
operation changes to a jerky, slow operation.. with upwards of 5 second
pauses in reads.


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