Re: tuning hints for PAE

On Thu, 15 Jul 2004, Daniel Lang wrote:

> My values are the following (with adjusted maxvnodes):
> [..]
> kern.maxvnodes: 64000
>       vnodes    35     7K      7K      166  16,32,64,128,256
> kern.minvnodes: 52958
> vm.stats.vm.v_vnodein: 568488
> vm.stats.vm.v_vnodeout: 1
> vm.stats.vm.v_vnodepgsin: 1384470
> vm.stats.vm.v_vnodepgsout: 1
> vfs.numvnodes: 190867
> vfs.wantfreevnodes: 25
> vfs.freevnodes: 135112
> debug.sizeof.vnode: 264
> [..]
>
> So the actual consumed memory (7k ?) appears neglectible.
> However, kern.minvnodes has nearly reached the now upper limit,
> so maybe trimming maxvnodes to 64000 was maybe too small,
> and the saved space appears not worth the effort?
>
> I will bump it up a bit more...
>
> What about the 35 vnodes "In Use" (reported by kern.malloc) but
> vfs.numvnodes: 190867, I am not sure how to interpret these
> values....
>
> As far as I understand it, a vnode is a kernel data-structure
> referring to a file-like entity (file, directory, socket, pipe, etc).
> So there are obviously much more in use than 35. 190867 appears
> too much, for ~ 400 active processes. Even if there are many
> filedescriptors open by each process, it is probably much less than 500
> per process. But maybe if these include all cached vnodes, so
> all vnodes which have been in use in the past, it could fit.
>
> Sorry for being not too educated about this really basic
> UNIX concept. :-}

Daniel,

If you are running a lot of dynamically-linked programs, an fd is 
allocated for every library that is imported. If you really want to find 
out what's going on where as far as fds on your system, lsof(8) from ports 
is your friend. Vnodes, are kernel-land structures that can reference any 
file or directory. Your vnode use count is always going to be greater than 
the number of open fds on your system. The two are somewhat related 
because you're guaranteed to have a vnode allocated for every file that is 
opened and for each process' current working directory (In the case of 
multiple programs accessing the same file or directory, the kernel 
increments the given vnode's reference count). The kernel keeps a vnode 
cache in order to limit the number of expensive lookups that would 
otherwise have to be performed while heavy I/O is under way.

The namei(9) and vnode(9) manpages contain a wealth of information on the 
matter.

I hope this helps. :)

Regards,
Andy

> Andre Guibert de Bruet | Enterprise Software Consultant >
> Silicon Landmark, LLC. | http://siliconlandmark.com/    >