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

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Message-ID: <4FFE9321.9070901@redhat.com>
Date:	Thu, 12 Jul 2012 12:04:33 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Tomoki Sekiyama <tomoki.sekiyama.qu@...achi.com>
CC:	jan.kiszka@...mens.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	yrl.pp-manager.tt@...achi.com
Subject: Re: [RFC PATCH 00/18] KVM: x86: CPU isolation and direct interrupts
 handling by guests

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


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