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Re: Migration - Xen 4.3

On Tue, 20 Jan 2015, Jean-Yves Migeon wrote:
I have never got migration to succeed, nor suspend/resume (which is
fundamentally the same operation). Sometimes suspend appears to work,
but resume fails.

The usual symptoms for me are that the domain just continues
regardless (i.e. it ignores the suspend request) rather than it locks.
However, from a dom0 point of view, it waits for confirmation of
suspension and so blocks any further operations on it.

I understand that the problem is reasonably well understood by the
relevant developers, but that debugging is hard.

Now that's a regression, suspend is supposed to finish correctly (e.g. the domain is descheduled and you get a core file that represents VM's state). Resuming is the culprit and I failed to get $SPARETIME to investigate the situation in the last few months; usual symptoms is a corrupted Xen I/O ring that completely thrashes xbdback(4) and leads to a paniced domU (or a very, very slow dom0 like an interrupt storm).

Do you try suspend/resume on UP or MP domU?

OK, I tried again with latest -current/amd64 and suspend/resume did superficially work. Suspend was fine and it appeared to resume. du / was able to go through the whole FS, but networking was dead.
Also, I could not cleanly shut it down.

I tried again and then hit the xbd deadlock which panicked:
iostat_isbusy() at netbsd:iostat_isbusy
xbd_handler() at netbsd:xbd_handler+0x192

Out of interest, I tried migrating between two homogeneous hosts with the same results.

So no regression, but no progress, as expected.

Using xl or xm?

I'm using XenServer, so xapi rather than xl/xm.


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