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

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Message-ID: <4FEDC22F.9070406@redhat.com>
Date:	Fri, 29 Jun 2012 17:56:47 +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 06/29/2012 12:25 PM, Tomoki Sekiyama wrote:
> Hi, thanks for your comments.
>
> 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. But, as far as I saw, there are still major
> >> restrictions in this approach, e.g. that you can't return to userspace
> >> on the slave core. Or even execute the in-kernel device models on that core.
>
> 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.

>  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.


-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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