NFS issues since upgrading to 13-RELEASE

Rick Macklem rmacklem at
Thu Apr 15 21:05:28 UTC 2021

I wrote:
[stuff snipped]
>- Alternately you can try rscheff@'s alternate proposed patch that is at
>  https://reviews.freebsd.og/D29690.
Oops, that's


  I have not yet had time to test this one, but since I cannot reproduce the hang, I can
  only do testing of it to see that it is "no worse" than reverting r367492 for my

Please let us know which you choose and whether or not it fixes your problem.

>> Any pointers for troubleshooting this? I've been looking through vmstat, gstat, top, etc. when the problem occurs, but I haven't been able to pinpoint the issue. I can get pcap, but it would be from the hosts, because I don't have a 10G tap or managed switch.
>run `nfsstat -d 1` and try to capture a few lines from before, during,
>and after the stall, and that may provide some insight.
>Specifically, does the queue length grow, suggesting it is waiting on
>the I/O subsystem, or does it just stop getting traffic all together.

If the revert of r367492 does not fix the problem, monitor the TCP connection(s)
via "netstat -a" and, if possible, capture packets via
tcpdump -s 0 -w hang.pcap host <nfs-client>
or similar, run on the server.

Ideally the tcpdump would  be started before the "hang" occurs, but running
one while the hang is occurring (until after it recovers) could also be useful.

Thanks for reporting this, rick

Allan Jude
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