Re: [PATCH 2 of 2] Avoid vcpu migration of paused vcpus

[Juergen Gross <juergen.gross@ts.fujitsu.com>]

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On 03/22/2012 12:20 PM, Keir Fraser wrote:
> On 22/03/2012 10:22, "Juergen Gross"<juergen.gross@ts.fujitsu.com>  wrote:
>
>> On 03/22/2012 11:12 AM, Keir Fraser wrote:
>>> Your original patch didn't touch this code. Was that an omission in the
>>> original version? On reflection I prefer your original patch to this new
>>> approach. I'll apply it if you still believe your original patch is complete
>>> and correct as it stands.
>> I like my second patch more :-)
>>
>> It covers more cases, not just poweroff. In hibernate case no vcpu pinnings
>> will be lost. Today all vcpus pinned to a cpu other than 0 will lose their
>> pinnings at cpu offlining. At reactivation those pinnings will not be
>> restored automatically. My patch will cover that by checking availability
>> of the cpus after reactivation.
>>
>> Poweroff (which was my primary concern) works with both versions. I did not
>> test other ACPI state changes with either version, but would expect better
>> results in hibernate case with my second approach.
> How about the attached patch? Which is similar to your original patch except
> I added the global state variable, and I added a check for it to
> cpu_disable_scheduler(). It's nice and small. :-)

And it works in all of my test cases for poweroff. :-)

Acked-by: Juergen Gross <juergen.gross@ts.fujitsu.com>


Thanks, Juergen

>   -- Keir
>
>> Juergen
>>
>>>    -- Keir
>>>
>>> On 22/03/2012 08:22, "Juergen Gross"<juergen.gross@ts.fujitsu.com>   wrote:
>>>
>>>> Currently offlining a cpu will migrate all vcpus which were active on that
>>>> cpu to another one, possibly breaking existing cpu affinities.
>>>>
>>>> In case of an ACPI state change the cpus are taken offline and online later
>>>> (if not poweroff) while all domains are paused. There is no reason to
>>>> migrate the vcpus during offlining the cpus, as the cpus will be available
>>>> again when the domains are being unpaused.
>>>>
>>>> This patch defers the migration check in case of paused vcpus or domains
>>>> by adding vcpu_arouse() to wake up a vcpu and check whether it must be
>>>> migrated to another cpu.
>>>>
>>>> Signed-off-by: Juergen Gross<juergen.gross@ts.fujitsu.com>
>>>>
>>>>
>>>> 3 files changed, 64 insertions(+), 24 deletions(-)
>>>> xen/common/domain.c     |    4 +-
>>>> xen/common/schedule.c   |   83
>>>> ++++++++++++++++++++++++++++++++++-------------
>>>> xen/include/xen/sched.h |    1
>>>>
>>>>
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>>>
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>
>
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-- 
Juergen Gross                 Principal Developer Operating Systems
PDG ES&S SWE OS6                       Telephone: +49 (0) 89 3222 2967
Fujitsu Technology Solutions              e-mail: juergen.gross@ts.fujitsu.com
Domagkstr. 28                           Internet: ts.fujitsu.com
D-80807 Muenchen                 Company details: ts.fujitsu.com/imprint.html


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