Hello,
Using this Qemu patchset as well as recent irqfd work, I’ve tried to make vhost-net working on Cortex-A15.
Unfortunately, even if I can correctly generate irqs to the guest through irqfd, it seems to me that some pieces are still missing….
Indeed, virtio mmio interrupt status register (@ offset 0x60) is not updated by vhost thread, and reading it or writing to the peer interrupt ack
register (offset 0x64) from the guest causes an VM exit …
After reading older posts, I understand that vhost-net with irqfd support could only work with MSI-X support :
On 01/20/2011 09:35 AM, Michael S. Tsirkin wrote:
“When MSI is off, each interrupt needs to be
bounced through the io thread when it's set/cleared, so vhost-net causes more context switches and
higher CPU utilization than userspace virtio which handles networking in the same thread.
“
Indeed, in case of MSI-X support, Virtio spec indicates that the ISR Status field is unused…
I understand that Vhost does not emulate a complete virtio PCI adapter but only manage virtqueue operations.
However I don’t have a clear view of what is performed by Qemu and what is performed by vhost-thread…
Could someone highlight me on this point, and maybe give some clues for an implementation of Vhost with irqfd and without MSI support ???
Thanks a lot in advance.
Best regards.
Rémy
De : address@hidden [mailto:address@hidden
De la part de Yingshiuan Pan
Envoyé : vendredi 15 août 2014 09:25
À : Li Liu
Cc : address@hidden; address@hidden; qemu-devel
Objet : Re: [Qemu-devel] The status about vhost-net on kvm-arm?
Hi, Li,
It's ok, I did get those mails from mailing list. I guess it was because I did not subscribe some of mailing lists.
Currently, I think I will not have any plan to renew my patcheset since I have resigned from my previous company, I do not have Cortex-A15 platform to test/verify.
I'm fine with that, it would be great if you or someone can take it and improve it.
----
Best Regards,
Yingshiuan Pan
2014-08-15 11:04 GMT+08:00 Li Liu <address@hidden>:
Hi Ying-Shiuan Pan,
I don't know why for missing your mail in mailbox. Sorry about that.
The results of vhost-net performance have been attached in another mail.
Do you have a plan to renew your patchset to support irqfd. If not,
we will try to finish it based on yours.
On 2014/8/14 11:50, Li Liu wrote:
>
>
> On 2014/8/13 19:25, Nikolay Nikolaev wrote:
>> On Wed, Aug 13, 2014 at 12:10 PM, Nikolay Nikolaev
>> <address@hidden> wrote:
>>> On Tue, Aug 12, 2014 at 6:47 PM, Nikolay Nikolaev
>>> <address@hidden> wrote:
>>>>
>>>> Hello,
>>>>
>>>>
>>>> On Tue, Aug 12, 2014 at 5:41 AM, Li Liu <address@hidden> wrote:
>>>>>
>>>>> Hi all,
>>>>>
>>>>> Is anyone there can tell the current status of vhost-net on kvm-arm?
>>>>>
>>>>> Half a year has passed from Isa Ansharullah asked this question:
>>>>>
http://www.spinics.net/lists/kvm-arm/msg08152.html
>>>>>
>>>>> I have found two patches which have provided the kvm-arm support of
>>>>> eventfd and irqfd:
>>>>>
>>>>> 1) [RFC PATCH 0/4] ARM: KVM: Enable the ioeventfd capability of KVM on ARM
>>>>>
http://lists.gnu.org/archive/html/qemu-devel/2014-01/msg01770.html
>>>>>
>>>>> 2) [RFC,v3] ARM: KVM: add irqfd and irq routing support
>>>>> https://patches.linaro.org/32261/
>>>>>
>>>>> And there's a rough patch for qemu to support eventfd from Ying-Shiuan Pan:
>>>>>
>>>>> [Qemu-devel] [PATCH 0/4] ioeventfd support for virtio-mmio
>>>>>
https://lists.gnu.org/archive/html/qemu-devel/2014-02/msg00715.html
>>>>>
>>>>> But there no any comments of this patch. And I can found nothing about qemu
>>>>> to support irqfd. Do I lost the track?
>>>>>
>>>>> If nobody try to fix it. We have a plan to complete it about virtio-mmio
>>>>> supporing irqfd and multiqueue.
>>>>>
>>>>>
>>>>
>>>> we at Virtual Open Systems did some work and tested vhost-net on ARM
>>>> back in March.
>>>> The setup was based on:
>>>> - host kernel with our ioeventfd patches:
>>>>
http://www.spinics.net/lists/kvm-arm/msg08413.html
>>>>
>>>> - qemu with the aforementioned patches from Ying-Shiuan Pan
>>>>
https://lists.gnu.org/archive/html/qemu-devel/2014-02/msg00715.html
>>>>
>>>> The testbed was ARM Chromebook with Exynos 5250, using a 1Gbps USB3
>>>> Ethernet adapter connected to a 1Gbps switch. I can't find the actual
>>>> numbers but I remember that with multiple streams the gain was clearly
>>>> seen. Note that it used the minimum required ioventfd implementation
>>>> and not irqfd.
>>>>
>>>> I guess it is feasible to think that it all can be put together and
>>>> rebased + the recent irqfd work. One can achiev even better
>>>> performance (because of the irqfd).
>>>>
>>>
>>> Managed to replicate the setup with the old versions e used in March:
>>>
>>> Single stream from another machine to chromebook with 1Gbps USB3
>>> Ethernet adapter.
>>> iperf -c <address> -P 1 -i 1 -p 5001 -f k -t 10
>>> to HOST: 858316 Kbits/sec
>>> to GUEST: 761563 Kbits/sec
>> to GUEST vhost=off: 508150 Kbits/sec
>>>
>>> 10 parallel streams
>>> iperf -c <address> -P 10 -i 1 -p 5001 -f k -t 10
>>> to HOST: 842420 Kbits/sec
>>> to GUEST: 625144 Kbits/sec
>> to GUEST vhost=off: 425276 Kbits/sec
>
> I have tested the same cases on a Hisilicon board (address@hidden)
> with Integrated 1Gbps Ethernet adapter.
>
> iperf -c <address> -P 1 -i 1 -p 5001 -f M -t 10
> to HOST: 906 Mbits/sec
> to GUEST: 562 Mbits/sec
> to GUEST vhost=off: 340 Mbits/sec
>
> 10 parallel streams, the performance gets <10% plus:
> iperf -c <address> -P 10 -i 1 -p 5001 -f M -t 10
> to HOST: 923 Mbits/sec
> to GUEST: 592 Mbits/sec
> to GUEST vhost=off: 364 Mbits/sec
>
> I't easy to see vhost-net brings great performance improvements,
> almost 50%+.
>
> Li.
>
>>>
>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> kvmarm mailing list
>>>>> address@hidden
>>>>>
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
>>>>
>>>>
>>>> regards,
>>>> Nikolay Nikolaev
>>>> Virtual Open Systems
>>
>> .
>>
>
>
>
> .
>