# nfsd server cache flooded, try to increase nfsrc_floodlevel



## mikeshultz (Jul 12, 2011)

I ran into an issue today of our server thinking that it was being flooded and locking our nfs users out.  Got a LOT of these messages:


```
Jul 12 16:08:22 xxxxx kernel: nfsd server cache flooded, try to increase nfsrc_floodlevel
```

Our server:

```
[root@xxxxx /boot]# uname -a
FreeBSD xxxxx 8.2-RELEASE-p2 FreeBSD 8.2-RELEASE-p2 #0: Tue Jun 21 16:52:27 MDT 2011     yyy@xxxxx:/usr/obj/usr/src/sys/PEZ  amd64
```

I could find no information on nfsrc_floodlevel other than source code which didn't explain too much about it.  I don't know if it's a kernel config var, or what.

nfsstat -e did show this:


```
CacheSize   TCPPeak
    16385     16385
```

The source code and this output suggest that we're just running into the limit.  However, a comment in that source does suggest that "The cache will still function over flood level" but that doesn't seem to be the case.  I ended up having to revoke the clients and restarting nfsd to get it operational again.

I would appreciate anyone that could clarify what nfsrc_floodlevel is and how to go about changing it.


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## mikeshultz (Aug 9, 2011)

To anyone coming across this thread, it ended up being a bug in the Ubuntu Linux kernel of the client machine(s).  They wouldn't clear their own locks.  Once we upgraded, all returned to normal.  

Though this really seems like a nice DOS vector in NFS if it allows this...


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## boss_aus (May 28, 2019)

Well, 8 years later the same issue again. I have an Ubuntu client and NFS on FreeBSD 10 and server log has those errors:


> nfsd server cache flooded, try increasing vfs.nfsd.tcphighwater


At the same time on client's side nfs mount become unresponsive.


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## SirDice (May 28, 2019)

FreeBSD 10 has been End-of-Life since October 2018 and is not supported any more, you should upgrade. FreeBSD 11.3 will be released soon, that's probably a good time. 









						FreeBSD 11.3 Release Process
					

FreeBSD is an operating system used to power modern servers, desktops, and embedded platforms.




					www.freebsd.org
				




Topics about unsupported FreeBSD versions








						Unsupported FreeBSD Releases
					

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					www.freebsd.org


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## boss_aus (May 29, 2019)

Sorry, I posted the wrong version. My FreeBSD version is 11.2-RELEASE-p8


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## SirDice (May 29, 2019)

Have you tried increasing vfs.nfsd.tcphighwater as mentioned in the error?


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## boss_aus (Jun 25, 2019)

Well, I tried and I have found that the initial value is 0. I have set it to 4096 but I am not sure. What would be the good value to start ?


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