per-mount maxvnodes

[Emmanuel Dreyfus <manu%netbsd.org@localhost>]

Hello

For now the kernel has a global maxvndes limit, and starts reclaiming
vnodes once the limit is reached. That means unused vnodes will remain
for a while in the kernel. This may be a problem for userland filesystems,
since they hold memory for that vnodes. For instance, perfused grows 
and crash after a while because it exhausts the swap.

One solution is to lower kern.maxvnodes, but the consequence is 
that all filesystems are impacted. Therefore comes the idea to 
have a per-mount maxvnodes.

I tried implementing it, the biggest problem is how to set the value.
mount(2) only allows and int to be passed to the filesystem for 
mount options, there seems to be no way to pass a numeric option.
Any idea on that front?

-- 
Emmanuel Dreyfus
manu%netbsd.org@localhost