Major issues with nfsv4

[Rick Macklem]

If you can do so when the "Opens" count has gone fairly high,
please "sysctl vfs.deferred_inact" and let us know what that
returns.

rick

________________________________________
From: J David <j.david.lists at gmail.com>
Sent: Sunday, December 13, 2020 10:51 PM
To: Konstantin Belousov
Cc: Rick Macklem; freebsd-fs at freebsd.org
Subject: Re: Major issues with nfsv4

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On Sun, Dec 13, 2020 at 4:25 PM Konstantin Belousov <kostikbel at gmail.com> wrote:
> Nullfs with -o nocache (default for NFS mounts) should not cache vnodes.
> So it is more likely a local load that has 130k files open.  Of course,
> it is the OP who can answer the question.

This I can rule out; there is no visible correlation between "Opens"
and the number of files open on the system.

Just finishing a test right now, and:

$ sudo nfsstat -E -c | fgrep -A1 OpenOwner
    OpenOwner        Opens    LockOwner        Locks       Delegs     LocalOwn
         4678        36245           15            6            0            0
$ sudo fstat  | wc -l
    2698
$ ps Haxlww | wc -l
    1012

The value of Opens increases consistently over time.

Killing the processes causing this behavior *did not* reduce the
number of OpenOwner or Opens.

Unmounting the nullfs mounts (after the processes were gone) *did*:

$ sudo nfsstat -E -c | fgrep -A1 OpenOwner
    OpenOwner        Opens    LockOwner        Locks       Delegs     LocalOwn
          130           41            0            0            0            0

Mutex contention was observed this time, but once it was apparent that
"Opens" was increasing over time, I didn't let the test get to the
point of disrupting activities.  This test ended at Opens = 36589,
which is well short of the previous 130,000+.  It is possible that
mutex contention becomes an issue once system CPU resources are
exhausted.

More about the results of the latest test after the data is analyzed.

After that's done, I'll attempt Rick's patch.  In the long run, we
would definitely like to get delegation to work.  Baby steps!

Thanks!