Re: [Qemu-devel] [patch 0/3] kvmclock: Ensure time in migration never goes backward (v3)

[Andrey Korolyov]

On Fri, Sep 5, 2014 at 10:35 PM, Andrey Korolyov <address@hidden> wrote:
> On Fri, Sep 5, 2014 at 10:26 PM, Marcelo Tosatti <address@hidden> wrote:
>> On Fri, Sep 05, 2014 at 10:16:17PM +0400, Andrey Korolyov wrote:
>>> On Fri, Sep 5, 2014 at 5:52 PM, Marcelo Tosatti <address@hidden> wrote:
>>> > Regression fix tested with fio and ping-pong migration.
>>> >
>>> >
>>>
>>> Thanks, actually this series also introduces regression with average
>>> live migration time - 42s avg vs 7s avg for the reference VM on
>>> ping-pong test. Can you please confirm this?
>>
>> Can't confirm - migration time is similar for me.
>>
>> What workload are you using?
>>
>
> Just an 'empty' VM on reference test and fio tests at the
> patch-specific test suite. Actual presence of workload brings
> difference for about 2s, effectively unmeasurable on a small series of
> 40+s migration times.

Heh... hit independent bug due to different pre-test conditions, the
patch itself is ok.

Bug follows:
- boot up a VM, make sure to feed it heavy long task, for example
kernel compilation,
- neither migrate once in the middle of process (with fallback to
non-live migration which is available in libvirt, else it may take
forever) or just wait up to the end,
- live migration time degrades from sub-10s value to larger values
forever, not regarding if workload is still presented or not.