Re: [Xen-devel] [xen-unstable test] 128240: regressions - FAIL

[Juergen Gross <jgross@xxxxxxxx>]

On 01/10/2018 17:48, George Dunlap wrote:
> On 10/01/2018 04:40 PM, Andrew Cooper wrote:
>> On 01/10/18 16:35, Wei Liu wrote:
>>> On Mon, Oct 01, 2018 at 04:19:07PM +0100, George Dunlap wrote:
>>>> On 10/01/2018 04:17 PM, Wei Liu wrote:
>>>>> On Mon, Oct 01, 2018 at 09:10:25AM -0600, Jan Beulich wrote:
>>>>>>>>> On 01.10.18 at 16:33, <wei.liu2@xxxxxxxxxx> wrote:
>>>>>>> On Mon, Oct 01, 2018 at 03:04:02AM -0600, Jan Beulich wrote:
>>>>>>>>>>> On 30.09.18 at 23:59, <osstest-admin@xxxxxxxxxxxxxx> wrote:
>>>>>>>>> flight 128240 xen-unstable real [real]
>>>>>>>>> http://logs.test-lab.xenproject.org/osstest/logs/128240/ 
>>>>>>>>>
>>>>>>>>> Regressions :-(
>>>>>>>>>
>>>>>>>>> Tests which did not succeed and are blocking,
>>>>>>>>> including tests which could not be run:
>>>>>>>>>  test-amd64-amd64-migrupgrade 22 guest-migrate/src_host/dst_host fail 
>>>>>>>>> REGR. vs. 
>>>>>>> 128084
>>>>>>>> At the first glance
>>>>>>>>
>>>>>>>> libxl: error: libxl_sched.c:232:sched_credit_domain_set: Domain 
>>>>>>>> 1:Getting 
>>>>>>> domain sched credit: Invalid argument
>>>>>>>> libxl: error: libxl_create.c:1275:domcreate_rebuild_done: Domain 
>>>>>>>> 1:cannot 
>>>>>>> (re-)build domain: -3
>>>>>>>> might indicate a problem resulting from the switch to credit2 as the 
>>>>>>>> default
>>>>>>>> scheduler. But "first glance" here really means what it says - I 
>>>>>>>> didn't look
>>>>>>>> (yet) at what exactly libxl tries to do there, in the hope that others 
>>>>>>>> may
>>>>>>>> know without much digging.
>>>>>>> I think this is due to toolstack trying to set the same scheduler
>>>>>>> parameters for the newly created guest.
>>>>>>>
>>>>>>> But in this test, the destination host is using a different scheduler
>>>>>>> from the source host. Asking for credit scheduler on a credit2 host is
>>>>>>> wrong.
>>>>>>>
>>>>>>> The relevant snippet in guest cfg (JSON) is:
>>>>>>>
>>>>>>>                 "sched_params": {
>>>>>>>                     "sched": "credit",
>>>>>>>                     "weight": 256,
>>>>>>>                     "cap": 0
>>>>>>>                 },
>>>>>>>
>>>>>>> I can't think of a method to fix it off the top of my head though.
>>>>>> So is this something that was specified in the original config? Or
>>>>>> is it just the current value which gets read and an attempt made
>>>>>> to re-install. If there was no explicit setting in the guest config,
>>>>>> shouldn't such a "default" setting be retained by not transferring
>>>>>> any scheduler specifics during migration?
>>>>>>
>>>>> No setting in guest cfg. Those values are extracted from the hypervisor.
>>>>> I think we may be able to not send default values to the remote end.
>>>> Wait, the migration code reads the scheduler parameters -- even if these
>>>> have not been explicitly set by the admin -- and sends them along with
>>>> the migration stream?  And if the remote scheduler is different, the
>>>> migration fails?
>>>>
>>>> That's not so good. :-)
>>> But one can argue that the guest is specific configured that way so it's
>>> parameters should be preserved. We normally analyse things on a case by
>>> case basis.
>>
>> If there isn't an obvious fix, then the switch of default scheduler
>> needs reverting until there is a fix present.  This is currently
>> blocking master.
> 
> Agreed.  I'd argue for ignoring failures to set scheduler parameters on
> migrate, on the grounds that this will be less risk to the project as a
> whole than reverting credit2 again.  But either way we should do
> something quickly.

We should ignore a mismatch of the scheduler. Failures when setting
parameters for a matching scheduler should not be ignored IMO.


Juergen

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