UI freezes while copying large file via NFS

[Patrick O'Callaghan]

On Mon, 2010-08-09 at 13:45 -0700, Konstantin Svist wrote:
> On 08/09/2010 12:36 PM, Patrick O'Callaghan wrote:
> > I've been copying some large (several GB) files from my local system to
> > a NAS server on my LAN, using NFS.
> >
> > The local files are on an external USB drive (Iomega 500GB unit) on a
> > USB 2 port. The NAS server is also Iomega, an ix-200. The network switch
> > is a Belkin Wireless G with 100Mbps Ethernet ports (I'm not using Wifi
> > for this). I'm not using jumbo frames or anything fancy, in fact I don't
> > think the Belkin supports them. The system is an Intel Core 2 Duo mobo
> > with 4GB RAM running F13 fully updated.
> >
> > I'm using KDE 4.4.5. When I do one of these copies (using cp from a
> > terminal), my entire system becomes unresponsive for periods of about 1
> > minute, then becomes usable for maybe 10 seconds, freezes again for
> > another minute etc. etc. until the copy finishes. "Unresponsive" means
> > the mouse cursor won't move, button clicks aren't attended to and I
> > can't type in Konsole or in the Evolution mail composer.
> >
> > Copying the same files to a local SATA disk doesn't cause this
> > phenomenon, so it can't just be the external drive. OTOH, I use the same
> > NAS for regular rsync-based backups *to the same NFS-mounted NAS* and
> > the load is not noticeable.
> >
> > Any thoughts on this would be welcome.
> >
> > poc
> 
> Usually you see this kind of problem when your HDD is thrashing.
> 
> Try running your copy command with ionice:
> ionice -c3 <command>

OK, I tried that with a 1.2GB file. The mouse didn't freeze but I still
couldn't do anything for long periods, as before.

> Other things to check:
> * run top in a separate window before you run the freezing command -- 
> see what it says when it works

It freezes :-) i.e. it fails to update the status except every minute or
so. When it does update, I can see the load average going up (over 4 in
this case, on a more or less idle system). CPU wasn't being saturated or
anything.

> * see if tty sessions in Ctrl+Alt+F2..F6 respond any better than the UI

Also frozen.

poc