Re: [Xen-devel] soft lockups during live migrate..

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 23:16 +0100 on 23 Oct (1256339811), Mukesh Rathor wrote:
> On Fri, 23 Oct 2009 11:09:36 +0100
> Tim Deegan <Tim.Deegan@xxxxxxxxxx> wrote:
> 
> > At 05:21 +0100 on 23 Oct (1256275309), Mukesh Rathor wrote:
> > > Trying to migrate a 64bit PV guest with 64GB running medium to
> > > heavy load on xen 3.4.0, it is showing lot of soft lockups. The
> > > softlockups are causing dom0 reboot by the cluster FS. The hardware
> > > has 256GB and 32 CPUs.
> > > 
> > > Looking into the hypervisor thru kdb, I see one cpu in
> > > sh_resync_all() while all other 31 appear spinning on the
> > > shadow_lock.
> > 
> > How many vcpus does the guest have?  Scalability issues in the OOS
> > shadow code are more related to number of VCPUs than amount of RAM.
> 
> Actually, things are fine with 32GB/32vcpus. Problem happens with
> 64GB/32vcpus. Trying the unstable version now.

Interesting.  Have you tried increading the amount of shadow memeory 
you give to the guest?  IIRC xend tries to pick a sensible default but
if it's too low and you start thrashing things can get very slow indeed.

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Citrix Systems (R&D) Ltd.
[Company #02300071, SL9 0DZ, UK.]

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