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From: John Snow <jsnow@redhat.com>
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Date: Tue, 6 Oct 2015 19:02:51 -0400
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Subject: Re: [Qemu-devel] Debugging Migration
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To: "Denis V. Lunev" <den-lists@parallels.com>, qemu-devel <qemu-devel@nongnu.org>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>



On 10/06/2015 06:40 PM, Denis V. Lunev wrote:
> On 10/06/2015 09:46 PM, John Snow wrote:
>> Is there a convenient way of "pausing" or stalling a live migration to
>> allow methodical testing of race conditions?
>>
>> I'd like to instrument something along the lines of:
>>
>> (1) Live migration begins.
>> (2) migration is artificially halted or paused, but QEMU is allowed to
>> run.
>> (3) Some additional qtest/QMP commands are received and processed.
>> (4) migration is allowed to resume.
>>
>> Does anyone have perhaps even test patches to instrument this sort of
>> thing, or is it up to detective john to add it if he wants it?
>>
>> Thanks,
>> --js
>>
> we have performed some experiments with migration "test mode".
> The idea was to estimate the time to migrate and estimate
> expected downtime for distributed resource management.
> In this mode the migration was not performed but all stuff around
> like dirty bitmap was touched.
> 
> There are several patches for this in my queue but they are very
> hackish.
> 
> Will it help you?
> 
> Den

It certainly won't hurt me to look at them if you'll share :)

--js