Public bug reported:
I have a file server running Ubuntu 18.04 LTS which has strange behavior
with systemd and dbus during heavy I/O load. The file server is set up
with RAID60 with mdadm serving via NFS. When I/O load becomes high, it
appears that dbus and systemd-logind are slowing down for SSH
connections and I lose SSH connectivity due to login failure with
pam_systemd:
Oct 19 11:14:56 nfsserver sshd[20635]: pam_systemd(sshd:session): Failed to
create session: Connection timed out
Oct 19 11:15:06 nfsserver sshd[20821]: pam_systemd(sshd:session): Failed to
create session: Connection timed out
Oct 19 11:15:06 nfsserver sshd[20837]: pam_systemd(sshd:session): Failed to
create session: Connection timed out
Oct 19 12:05:58 nfsserver sshd[25143]: pam_systemd(sshd:session): Failed to
create session: Connection timed out
Oct 19 13:03:07 nfsserver sshd[47296]: pam_systemd(sshd:session): Failed to
release session: Connection timed out
Oct 19 13:05:39 nfsserver sshd[48532]: pam_systemd(sshd:session): Failed to
create session: Message recipient disconnected from message bus without replying
Oct 19 13:05:39 nfsserver sshd[48570]: pam_systemd(sshd:session): Failed to
create session: Message recipient disconnected from message bus without rep
CPU load gets near 50 or 60%, but not 100%. Looking through bug reports
and issues that others have experienced with previous versions, it seems
that when systemd-logind doesn't process the IPC queue from dbus fast
enough, dbus will kick systemd-logind resulting in this failure. This
appears to be so in socket statistics whereby the dbus IPC Send-Q fills
and does not move during heavy load:
Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port
u_str ESTAB 0 153088 /var/run/dbus/system_bus_socket -2002184190 * -2002209306
The Recv-Q on the other end does not keep up:
Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port
u_str ESTAB 37892 0 * -2002209306 * -2002184190
I have tried to renice dbus, systemd, systemd-logind without success.
The only way to resolve this issue is to reduce I/O load. Any thoughts?
** Affects: systemd (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1798883
Title:
Ubuntu 18.04 LTS: pam_systemd: Failure to create session under heavy
I/O load
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