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[Xen-devel] freezing when using GPLPV drivers (including Dom0)

  • To: <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
  • Date: Wed, 31 Dec 2008 13:46:04 +1100
  • Delivery-date: Tue, 30 Dec 2008 18:46:32 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: Aclq8extx1AIvKo+Ql6WikxbNr/6rg==
  • Thread-topic: freezing when using GPLPV drivers (including Dom0)

I'm trying to resolve an issue in my GPLPV drivers that has come about
in doing some restores using Backup Exec across the network.

The server running Backup Exec can be a DomU or a completely separate
machine (connected via gigabit Ethernet).

When restoring a large file (30G exchange mailbox store), everything
locks up for a bit, long enough for ARP to timeout and the TCP
connection for the backup data to drop, failing the backup. This can
happen anywhere from 500MB to 20G into the restore, but normally around
the 2G mark.

Investigating is a bit tricky as even Dom0 is not usable - any command I
type at a shell doesn't do anything until it unfreezes. When everything
comes back, it all comes back at once. There are no messages in the
kernel logs or the xen logs.

I am suspecting that maybe the problem is disk starvation but I don't
quite understand why the lockup happens for so long. I'm also not sure
why I'm only seeing the problem when using my GPLPV drivers - one
possibility is that the increased performance puts more load on the
storage system.

Any suggestions?



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