Nullfs leaks i-nodes

[Dewayne Geraghty]

> -----Original Message-----
> From: owner-freebsd-stable at freebsd.org 
> [mailto:owner-freebsd-stable at freebsd.org] On Behalf Of Mikolaj Golub
> Sent: Wednesday, 8 May 2013 6:42 AM
> To: Göran Löwkrantz
> Cc: Kostik Belousov; freebsd-stable at freebsd.org
> Subject: Re: Nullfs leaks i-nodes
> 
> On Tue, May 07, 2013 at 08:30:06AM +0200, Göran Löwkrantz wrote:
> > I created a PR, kern/178238, on this but would like to know 
> if anyone has 
> > any ideas or patches?
> > 
> > Have updated the system where I see this to FreeBSD 
> 9.1-STABLE #0 r250229 
> > and still have the problem.
> 
> I am observing an effect that might look like inode leak, which I
> think is due free nullfs vnodes caching, recently added by kib
> (r240285): free inode number does not increase after unlink; but if I
> purge the free vnodes cache (temporary setting vfs.wantfreevnodes to 0
> and observing vfs.freevnodes decreasing to 0) the inode number grows
> back.
> 
> You have only about 1000 inodes available on your underlying fs, while
> vfs.wantfreevnodes I think is much higher, resulting in running out of
> i-nodes.
> 
> If it is really your case you can disable caching, mounting nullfs
> with nocache (it looks like caching is not important in your case).
> 
> -- 
> Mikolaj Golub
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Hi Goran,

After I included Kib's vnode caching patch the performance on my "port builder" machine, decreased significantly.  The "port
builder" is one of many jails and nullfs is used extensively. I was starving the system of vnodes.  Increasing the kern.maxvnodes,
resulted in better performance than the original system configuration without vnode caching. Thanks Kib :)

I don't think you'll run out of vnodes as it is self adjusting (that was my concern too)

I changed kern.maxvnode to approx 3 times what it wanted and tuned for my needs.
Try it and keep an eye on:
sysctl vfs.numvnodes vfs.wantfreevnodes vfs.freevnodes vm.stats.vm.v_vnodepgsout vm.stats.vm.v_vnodepgsin

Regards, Dewayne