An interesting anomaly in NFS client...

From: George Neville-Neil <gnn_at_neville-neil.com>
Date: Thu, 07 Nov 2024 00:43:27 UTC
Howdy,

We've been digging into an interesting possible issue in the FreeBSD NFS 
client.  Here is the scenario.  I have a FreeBSD VM on my Mac, the Mac 
is the NFS server, the VM is the client.  I then attempt to build an out 
of tree kernel module that I'm working on.  The build looks like it's 
hanging for 1.5 seconds, and when we look at the packets (pcap file 
attached) we see a ton of GETATTRs over the first 1.5 seconds.  I've put 
the pcap up here: 
[oct_8_2024.pcapng](https://people.freebsd.org/~gnn/oct_8_2024.pcapng)

I also note that an issue was raised on the forums that seems similar, 
way back between FreeBSD 10 and 11:

https://forums.freebsd.org/threads/nfs-cache-misses-after-upgrading-to-11-1-from-10-3.65491/

I'm seeing this on 15 currentish (last few months).

Best,
George