[slurm-users] X11 performance terrible using plugin

On our cluster we've noticed that if we use the native x11 slurm plugin (PrologFlags=x11) then X applications work, but are really slow and unresponsive. Even opening menus on graphical application is painfully slow.

On the same system if I do a direct ssh connection with ssh -YC from the head node the same applications are quick and responsive.

Any suggestions for what might be causing this, and how I can get the native x11 to have the same responsiveness as a direct ssh connection?

Many thanks

Simon.