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Date:      Fri, 6 Jan 2017 11:18:46 +0000
From:      'Roger Pau =?iso-8859-1?Q?Monn=E9'?= <roger.pau@citrix.com>
To:        Jay West <jwest@ezwind.net>
Cc:        "'Hoyer-Reuther, Christian'" <Christian.Hoyer-Reuther@cac-chem.de>, <freebsd-xen@freebsd.org>, <owner-freebsd-xen@freebsd.org>
Subject:   Re: 11-RELEASE and live migration
Message-ID:  <20170106111846.qnvrq6vwvdi3245y@dhcp-3-221.uk.xensource.com>
In-Reply-To: <001701d2679d$f99eb560$ecdc2020$@ezwind.net>
References:  <001f01d250a6$05ca4160$115ec420$@ezwind.net> <a8486e84c86c73ae1a7d68a06d969671@ultra-secure.de> <003501d250af$032dd580$09898080$@ezwind.net> <41E487BC91654544B2B8F31096F2D9D4D1B060A925@ex1> <20161212103148.5prkggi3ix4zoxyv@dhcp-3-221.uk.xensource.com> <41E487BC91654544B2B8F31096F2D9D4D1B060AA3E@ex1> <002101d25484$c0a068c0$41e13a40$@ezwind.net> <20161214140224.rbg5h3v2opa3q3sj@dhcp-3-221.uk.xensource.com> <41E487BC91654544B2B8F31096F2D9D4D1B060ABBF@ex1> <001701d2679d$f99eb560$ecdc2020$@ezwind.net>

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On Thu, Jan 05, 2017 at 03:52:13PM -0600, Jay West wrote:
> 
> Roger wrote...
> > I'm able to see these glitches, as said the VM doesn't really hang, it 
> > just gets stuck for a long time (and I think that depends on the 
> > uptime differences between the source and destination hosts). In the 
> > meantime, could you please test if changing the timecounter from 
> > XENTIMER to any other (like HPET or
> > ACPI-fast) solves the issue?
> > 
> > # sysctl -w kern.timecounter.hardware=ACPI-fast
> 
> Christian replied...
> I changed the timecounter from XENTIMER to ACPI-fast and then I did about 10
> migrations between our 3 hosts. I always started the next migration a few
> seconds after the previous migration finished. The VM didn't stuck now and I
> didn't see the VGABios screen on the console.
> 
> I can also add to this... changing timecounter to ACPI-fast definitely fixes
> the problem. I can migrate a handful of freebsd11 vm's back and forth and
> all stay running correctly.
> 
> So... bug in XENTIMER?

Not exactly, let's say it's a shortcoming of the current resume procedure. IF
you want to know more about the gory details:

https://lists.freebsd.org/pipermail/freebsd-arch/2016-December/018041.html

I'm currently quite busy, so I don't really have an ETA of when this is going
to be fixed.

Roger.




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