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

[Keir Fraser <keir@xxxxxxx>]

On 22/03/2012 10:22, "Juergen Gross" <juergen.gross@xxxxxxxxxxxxxx> 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. :-)

 -- Keir

> 
> Juergen
> 
>>   -- Keir
>> 
>> On 22/03/2012 08:22, "Juergen Gross"<juergen.gross@xxxxxxxxxxxxxx>  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@xxxxxxxxxxxxxx>
>>> 
>>> 
>>> 3 files changed, 64 insertions(+), 24 deletions(-)
>>> xen/common/domain.c     |    4 +-
>>> xen/common/schedule.c   |   83
>>> ++++++++++++++++++++++++++++++++++-------------
>>> xen/include/xen/sched.h |    1
>>> 
>>> 
>>> _______________________________________________
>>> Xen-devel mailing list
>>> Xen-devel@xxxxxxxxxxxxx
>>> http://lists.xen.org/xen-devel
>> 
>> 
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxx
>> http://lists.xen.org/xen-devel
>> 
>> 
>

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