[Samba] Samba46 Listen queue overflow in FreeBSD 11.1

Wallace Barrow incin at incin.me
Tue Jan 16 19:08:21 UTC 2018

Hello everyone,

We are trying to track down some samba issues and wondering there are some 
settings we can tweak.

We have a new Supermicro server running the following with 192GB of RAM, 32
active CPUs and 54TB of usable zfs mirrors (raid10).

uname -a
FreeBSD hostname 11.1-RELEASE-p4 FreeBSD 11.1-RELEASE-p4 #0: Tue Nov 14 06:12:40 UTC 2017
root at amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC  amd64

[root at hostname /var/log]# freebsd-version -k

[root at hostname /var/log]# freebsd-version -u

Samba version = samba46-4.6.8

This server is hosting all data in ZFS pools. This server gives out NFS shares 
to other servers and holds the end user shares for Linux and Windows.

When the server is up for about 24 hours we start to see these errors in 
/var/log/messages. The occurrence number could be more.

kernel: sonewconn: pcb 0xfffff8018a4ba3c0: Listen queue overflow: 8 already in
queue awaiting acceptance (1 occurrences)

The load increases on the server by ~3 and more CPU is also used right after the
first error. After more time has past we slowly see more queue errors, maybe a
few every hour. After a few days the load reaches 20 and each CPU is running at
50%. It never goes above that.

Some info about that error:

[root at hostname /var/log]# netstat -anA | grep -i fffff8018a4ba3c0
fffff8018a4ba3c0 stream      0      0 fffff8016bc27938                0                0                0 /var/run/samba4/winbindd/pipe

[root at hostname /var/log]# sockstat -l | grep -i /var/run/samba4/winbindd/pipe
root     winbindd   1101  22 stream /var/run/samba4/winbindd/pipe
root     winbindd   1100  22 stream /var/run/samba4/winbindd/pipe
root     winbindd   1099  22 stream /var/run/samba4/winbindd/pipe
root     winbindd   962   22 stream /var/run/samba4/winbindd/pipe
root     winbindd   954   22 stream /var/run/samba4/winbindd/pipe

We have increased this kernel tuneable to --- kern.ipc.soacceptqueue=4096

The server is using the on board 10gig NIC which is know for a bug and a
different error. We turned off lso and tso to fix that error -
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=221919#c9 (my post in comment 

There have been other posts on the web about the "Listen queue overflow" errors
and having the NIC be the problem so for fun we installed a 1GB Intel PCI NIC
card just as a test with no luck, the errors came back after a day or so.

With all these errors in the logs you still can browse the shares in Windows or
Linux by \\sharename but when you login after a reboot or a log out the network
scripts time out mapping the drives so they don't appear to the end user, some
times if you are lucky you get the script to map the drives. Before there are
any errors about the queue, no issues.

Are there more kernel limits we should be adding? Can we adjust Samaba to accept
more connections or tune something there? After a 'service restart samba_server'
the load of the server goes back to normal, around 5, shares can be mapped by
scripts and the server is good for another 24 hours.



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