From: Dave Hansen <dave@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: kvm@vger.kernel.org, qemu-devel@nongnu.org,
Liu ping fan <kernelfans@gmail.com>,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
Avi Kivity <avi@redhat.com>,
Anthony Liguori <anthony@codemonkey.ws>
Subject: Re: [Qemu-devel] [PATCH 1/2] sched: add virt sched domain for the guest
Date: Wed, 23 May 2012 08:23:06 -0700 [thread overview]
Message-ID: <4FBD00DA.5080308@linux.vnet.ibm.com> (raw)
In-Reply-To: <1337762914.9698.65.camel@twins>
On 05/23/2012 01:48 AM, Peter Zijlstra wrote:
> On Wed, 2012-05-23 at 16:34 +0800, Liu ping fan wrote:
>> > so we need to migrate some of vcpus from node-B to node-A, or to
>> > node-C.
> This is absolutely broken, you cannot do that.
>
> A guest task might want to be node affine, it looks at the topology sets
> a cpu affinity mask and expects to stay on that node.
>
> But then you come along, and flip one of those cpus to another node. The
> guest task will now run on another node and get remote memory accesses.
Insane, sure. But, if the node has physically gone away, what do we do?
I think we've got to either kill the guest, or let it run somewhere
suboptimal. Sounds like you're advocating killing it. ;)
next prev parent reply other threads:[~2012-05-23 15:34 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-23 6:32 [Qemu-devel] [RFC] kvm: export host NUMA info to guest's scheduler Liu Ping Fan
2012-05-23 6:32 ` [Qemu-devel] [PATCH 1/2] sched: add virt sched domain for the guest Liu Ping Fan
2012-05-23 7:54 ` Peter Zijlstra
2012-05-23 8:10 ` Liu ping fan
2012-05-23 8:23 ` Peter Zijlstra
2012-05-23 8:34 ` Liu ping fan
2012-05-23 8:48 ` Peter Zijlstra
2012-05-23 9:58 ` Liu ping fan
2012-05-23 10:14 ` Peter Zijlstra
2012-05-23 15:23 ` Dave Hansen [this message]
2012-05-23 15:52 ` Peter Zijlstra
2012-05-23 6:32 ` [Qemu-devel] [PATCH 2/2] sched: add virt domain device's driver Liu Ping Fan
2012-05-23 6:32 ` [Qemu-devel] [PATCH] kvm: collect vcpus' numa info for guest's scheduler Liu Ping Fan
2012-05-23 6:32 ` [Qemu-devel] [PATCH] Qemu: add virt sched domain device Liu Ping Fan
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