Problems Re-Starting mountd

[Tim Gustafson]

> As I understood each /export/home/* pathname from /etc/exports is
> a mount point for ZFS file system.

Correct.

> I created 2000 file systems on ZFS file system backed by vnode md(4)
> device.  The /etc/exports file contains 4000 entries like your example.
>
> On 9.1-STABLE mountd spends ~70 seconds in flushing current NFS exports
> in the NFS server, parsing data from /etc/exports and loading parsed
> data into the NFS server.  ~70 seconds is not several minutes.  Most of
> time mountd spends in nmount() system call in "zio->io_cv" lock.

I suspect that statfs(), nmount() and lstat() will return much more
quickly for md-based file systems, since they have zero latency.

> Can you show the output of "truss -fc -o /tmp/output.txt mountd"
> (wait wchan "select" state of mountd and terminate it by a signal).
> If everything is correct you should see N statfs() calls, N+M nmount()
> calls and something*N lstat() calls, where N is the number of /etc/exports
> lines, M is the number of mounted file systems.  Number of lstat() calls
> depends on number of components in pathnames.

I will try to run this tonight; I can't do it now as people are
already starting to work today.

-- 

Tim Gustafson
tjg at soe.ucsc.edu
831-459-5354
Baskin Engineering, Room 313A