Message-ID: <54412AC6.7070000@cs.uchicago.edu>
Date: Fri, 17 Oct 2014 09:42:14 -0500
From: Colin Hudler <chudler@cs.uchicago.edu>
MIME-Version: 1.0
To: linux-nfs@vger.kernel.org
Subject: when rpc.mountd flushes auth.unix.gid
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Sender: linux-nfs-owner@vger.kernel.org

We have a few hundred computers mounting an NFS server in a typical 
LDAP-based users (nss) setup. We frequently add and remove exports and 
use exportfs -r to update etab. Every time we do so, the clients report 
"NFS server not responding" and start backing off their requests. After 
a painful 3-5 minutes, they recover and life is normal again.

We discovered that when the rpc.mountd cache flushing occurs, our NIS 
system is overwhelmed with grouplist requests and this obviously blocks 
things. We are working on that problem separately, and I admit this to 
be a weakness in our setup. My question is simple.

Why does it flush auth.unix.gid when the etab changed? I think it makes 
unnecessary work for rpc.mountd because the gids are unlikely to have 
changed, and they already have a reasonable expiration policy.

--
Colin