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

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Date:	Fri, 06 Jul 2012 19:33:00 +0900
From:	Tomoki Sekiyama <tomoki.sekiyama.qu@...achi.com>
To:	avi@...hat.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

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.

Thanks,
-- 
Tomoki Sekiyama <tomoki.sekiyama.qu@...achi.com>
Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory

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