Re: nfsd server cache flooded, try to increase nfsrc_floodlevel

Lars Eggert wrote:
> Hi,
> 
> every few days or so, my -STABLE NFS server (v3 and v4) gets wedged
> with a ton of messages about "nfsd server cache flooded, try to
> increase nfsrc_floodlevel" in the log, and nfsstat shows TCPPeak at
> 16385. It requires a reboot to unwedge, restarting the server does
> not help.
> 
> The clients are (mostly) six -CURRENT nfsv4 boxes that netboot from
> the server and mount all drives from there.
> 
> I googled around and saw that others have hit this issue, but I
> haven't seen any resolution posted. I guess I can increase
> NFSRVCACHE_FLOODLEVEL in the source, but I wonder if I wouldn't
> simply hit the increase value after a little while longer...
> 
> Lars
> 
You can either try this patch (which dynamically adjusts nfsrc_floodlevel
along with handling a variety of overhead issues for the DRC under heavy load):
   http://people.freebsd.org/~rmacklem/drc4.patch

or just bump it up a bunch. The default value was safe for a server with 256Mbytes
of ram and a default mbuf cluster limit. The only thing you might have to do
along with bumping NFSRC_FLOODLEVEL up is increasing kern.ipc.mbclusters.

The variant of the above patch will make it into head someday, once I merge
in changes from ivoras_at_'s similar patch and confer with him about it.

rick