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Re: [Xen-API] Guests running slowly after restart?

Hi dswartz,

Hopefully this is the right list for this, if not my apologies.  Anyway, I
am running XCP 1.6 on a xeon e3-1230 with 24MB RAM.  A handful of guests,
all but one of which are HVM (mainly because of lack of a good tool to PV
such guests) previously running under KVM.  One is windows 7 the others
various flavors of linux.  Anyway, I rebooted one of the guests (Astaro
Security Gateway) after an update.  It started booting, but very very
slowly.  Took almost 10 minutes to get a login prompt, when it usually
takes less than a minutes.  Once I was in, 'w' revealed a load factor of 8
or so, which was increasing as I was watching.  It wasn't (obviously)
paging, and oddly, xencenter claimed the guest was using 3% of 1 vCPU.  I
ended up having to reboot the host at which point all was well.  The same
thing happened about 12 hours later, at which point I tried restarting 2
of the other linux guests and saw the exact same behavior, so it wasn't
just ASG.  Again, a reboot 'fixed' this.  I have limited data points here,
but the problem seems to occur when (after some unknown amount of time), I
try to restart a guest.  Note that prior to restarting them, the guests
seem to be running just fine.  I am relatively new to Xen, so any clues
would be appreciated.  Thanks!

Could you check that iowait (the %wa in top) is not the culprit? That could explain that cpu consumption was low.

Not having PV drivers have a huge impact on disk and network io. CPU and mem will be fine, but if you have some process that have heavy io pattern, they can be brought to a crawl.

If your vms are not too old (2.6.18 and higher), you should probably try to switch to paravirt. For kernel <2.6.24, you'll have to select a specific xen enabled kernel, for more recent kernel it should work out of the box. You can follow the doc on http://forums.citrix.com/message.jspa?messageID=1005837

When switching to paravirt, your default console may switch to hvc0 and your drive names to xvdx, so check your grub, /etc/inittab and /etc/fstab.

Hope this helps,


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Denis Cardon
Tranquil IT Systems
Les Espaces Jules Verne, bâtiment A
12 avenue Jules Verne
44230 Saint Sébastien sur Loire
tel : +33 (0)

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