On Fri, 17 Oct 2014 21:21:18 -0500 Tom Haynes <thomas.haynes@xxxxxxxxxxxxxxx> wrote: > > On Oct 17, 2014, at 6:37 PM, Jeff Layton <jlayton@xxxxxxxxxxxxxxx> wrote: > > > On Fri, 17 Oct 2014 17:24:14 -0500 > > Tom Haynes <thomas.haynes@xxxxxxxxxxxxxxx> wrote: > > > >> > >> > >> > >>> On Oct 17, 2014, at 4:06 PM, Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx> wrote: > >>> > >>> On Fri, 17 Oct 2014 09:42:14 -0500 > >>> Colin Hudler <chudler@xxxxxxxxxxxxxxx> wrote: > >>> > >>>> 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. > >>> > >>> Most likely because no one really cared until now. > >>> > >>> When exports change, cache_flush() is called and that function flushes > >>> out all of the kernel caches. > >>> > >>> I expect that could be made to do something a bit more granular, but > >>> you may need to do some archaeology in mountd/exportfs (and the kernel) > >>> to ensure that you're not missing anything. > >>> > >> > >> One thing would be to not remove the exports which are going to be added back in. > >> > >> The catch here is that you have to account for new entries which need to be added. > >> > >> > > > > I'm not sure that flushing the uid or gid caches is really necessary on > > an exports change at all. I don't think we expect that info to change. > > Is there a manual way to flush these caches? > > Bump down the default TTL? > > The manual way is to write to /proc/net/rpc/*/flush (which is what cache_flush() in nfs-utils does). The comments over it say: /* flush the kNFSd caches. * Set the flush time to the mtime of _PATH_ETAB or * if force, to now. * the caches to flush are: * auth.unix.ip nfsd.export nfsd.fh */ ...but it looks like auth.unix.gid was added in 2007 and the comment wasn't updated. > > > > In practical terms, we might be able to change exportfs to just flush > > the nfsd.fh and nfsd.export caches instead of a full cache_flush() ? > > > > -- > > Jeff Layton <jlayton@xxxxxxxxxxxxxxx> > -- Jeff Layton <jlayton@xxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
