Re: [Xen-users] Frequent para (Linux) domU hangs

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Tue, Oct 06, 2009 at 03:26:05PM +1300, Jan Bakuwel wrote:
> Hi Nathan, all,
> 
> One thing I've just noticed: the two domU's that are frequently hanging
> are doing serious (database) I/O from time to time (not always but in
> bursts). Both have a relatively high VBD_OO, the domU that just hung had
> a VBD_OO of over 800 while the other domU's have very low VDB_OO (4 or 32).
> 
> I found this on the Internet:
> 
> http://lists.xensource.com/archives/html/xen-devel/2006-06/msg00812.html
> 
> Basically Satoshi suggests in his email that the underlying hardware is
> not able to keep up with the I/O requests of these particular domU's (if
> I read him well).
> 
> I wouldn't mind if the domU's simply slowed down if the hardware can't
> keep up... but in my case once they get "there", they hang and do not
> seem to return to normal (well we can't afford to wait for days).
> 
> Any suggestions to further diagnose (and fix? :-) ) this problem are
> very welcome.
> 

Just a thought; have you set up xen domain weights so that dom0 will
always have cpu time to process IO requests properly? ie. dom0 gets more
cpu than domUs.

-- Pasi

> kind regards,
> Jan
> 
> 
> 
> 
> Jan Bakuwel wrote:
> > Hi Nathan,
> >
> >   
> >> Dom0 is Debian Etch amd64 (haven't upgraded this Dom0 yet) running 
> >> 2.6.26-bpo.1-xen-amd64.  Xen version is xen-3.2-1-amd64.  Plenty of 
> >> leftover memory and swap.
> >>
> >> DomU is Centos 5.3 Final amd64, running the dom0's kernel 
> >> (2.6.26-bpo.1-xen-amd64).  DomU has lots of memory and plenty of swap 
> >> (added because I suspected it may have been a problem).
> >>
> >> One possibility I am beginning to suspect is that domU may be filling up 
> >> /tmp (using /usr/tmpDSK for some reason).  Not sure on that, though.  I 
> >> may try removing that from the fstab and see if stability improves...
> >>   
> >>     
> >
> > Seems like we're in a similar although not identical environment.
> >
> > I think there's not much difference (or perhaps none at all) between the
> > backported etch kernel and the lenny kernel?
> >
> > I've planned an upgrade to 2.6.26-2-xen-amd64 in the next few weeks to
> > see if that makes a difference and have just added a swapfile to one of
> > the two troubled VMs.
> >
> > Please keep me informed about your progress; I'll do the same.
> >
> > Jan
> >
> >
> > _______________________________________________
> > Xen-users mailing list
> > Xen-users@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-users
> >
> >   
> 
> 
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