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 : kvmarm-bounces@xxxxxxxxxxxxxxxxxxxxx [mailto:kvmarm-bounces@xxxxxxxxxxxxxxxxxxxxx] De la part de Yingshiuan Pan Envoyé : vendredi 15 août 2014 09:25 À : Li Liu Cc : kvmarm@xxxxxxxxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; 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. Thanks. ---- Best Regards, Yingshiuan Pan 2014-08-15 11:04 GMT+08:00 Li Liu <john.liuli@xxxxxxxxxx>: 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 >> <n.nikolaev@xxxxxxxxxxxxxxxxxxxxxx> wrote: >>> On Tue, Aug 12, 2014 at 6:47 PM, Nikolay Nikolaev >>> <n.nikolaev@xxxxxxxxxxxxxxxxxxxxxx> wrote: >>>> >>>> Hello, >>>> >>>> >>>> On Tue, Aug 12, 2014 at 5:41 AM, Li Liu <john.liuli@xxxxxxxxxx> 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 (Cortex-A15@1G) > 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 >>>>> kvmarm@xxxxxxxxxxxxxxxxxxxxx >>>>> https://lists.cs.columbia.edu/mailman/listinfo/kvmarm >>>> >>>> >>>> regards, >>>> Nikolay Nikolaev >>>> Virtual Open Systems >> >> . >> > > > > . > ��.n��������+%������w��{.n�����o�^n�r������&��z�ޗ�zf���h���~����������_��+v���)ߣ�
