Re: [RFC PATCH 00/18] KVM: x86: CPU isolation and direct interrupts handling by guests

Avi Kivity
2012-07-12T09:04:46Z

On 07/06/2012 01:33 PM, Tomoki Sekiyama wrote:
> Hi,
>
> On 2012/06/29 23:56, Avi Kivity wrote:
>>> On 2012/06/29 2:34, Avi Kivity wrote:
>>>> On 06/28/2012 08:26 PM, Jan Kiszka wrote:
>>>>>> This is both impressive and scary. What is the target scenario here?
>>>>>> Partitioning? I don't see this working for generic consolidation.
>>>>>
>>>>> From my POV, partitioning - including hard realtime partitions - would
>>>>> provide some use cases.
>>>
>>> Exactly this is for partitioning that requires bare-metal performance
>>> with low latency and realtime.
>>
>> It's hard for me to evaluate how large that segment is. Since the
>> patchset is so intrusive, it needs a large potential user set to
>> justify, or a large reduction in complexity, or both.
>
> Low latency or realtime is often required on high-end systems
> like trading, automated control, HPC and so on, or for multimedias.
> Those who want to run MRG as a guest, or to fully utilize high-speed
> NIC are also worth using this. And not all of such applications does
> not use up every CPU, so partitioning is becoming reasonable as a
> number of cores in a server is increasing.
> Anyway, I will try to make the patch as simple as possible.
>
>>> I think it is also useful for workload
>>> like HPC with MPI, that is CPU intensive and that needs low latency.
>>
>> I keep hearing about people virtualizing these types of workloads, but I
>> haven't yet understood why.
>
> One reason is ease of deployment of applications to nodes.
> Especially in IaaS environment like Amazon EC2 Cluster Compute Instances,
> virtualization is often introduced as a simple way to move applications
> around flexibly among nodes shared by many users.

Device assignment is not used in clouds yet, and you can't live migrate
if you use device assignment.

--
error compiling committee.c: too many arguments to function