qemu-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] multiprocessor on kvm


From: Xin Tong
Subject: Re: [Qemu-devel] multiprocessor on kvm
Date: Tue, 8 Nov 2011 09:21:26 -0500

now question is if one of the cpu vmexits the guest due to trapping
instruction ( i.e. PIO), the host linux will have only one physical
cpu to run on as the other cpus are still running the guest os ? Am I
right ?

Thanks


Xin

2011/11/8 Xin Tong <address@hidden>:
> so qemu exposes multiple processors to the guest os by having multiple
> vCPUs. and it realizes the multiple vCPUs by either using RR on a
> single host cpu (qemu ) or using multiple host cpus (kvm).
>
> Thanks
>
> Xin
>
>
> 2011/11/8 Stefan Hajnoczi <address@hidden>:
>> On Tue, Nov 8, 2011 at 12:10 PM, 陳韋任 <address@hidden> wrote:
>>> On Tue, Nov 08, 2011 at 08:04:44PM +0800, 陳韋任 wrote:
>>>> > I am wondering that when one uses qemu with kvm. How many cores are
>>>> > exposed and available to the guest os ( assuming the host has 4 cores
>>>> > ). is this configurable ?
>>>>
>>>>   QEMU provides "-smp" option, but those virtual cpus are scheduled in
>>>> round-robin fashion. In other words, it's not real parallelism. I don't
>>>> know if there is any difference with kvm enabled.
>>>
>>>  IIRC, kvm uses QEMU for device emulation only. Those virtual cpus are
>>> ran on physical cpus simultaneously.
>>
>> Right, qemu -enable-kvm will run a thread for each vCPU.  So you get
>> true SMP parallelism.
>>
>> QEMU without KVM mode, on the other hand, does round-robin scheduling
>> of vCPUs and does not take advantage of multiprocessor hosts.
>>
>> Stefan
>>
>



reply via email to

[Prev in Thread] Current Thread [Next in Thread]