Messages in this thread | | | From | 李菲 <> | Date | Mon, 22 Jul 2019 21:43:18 +0800 | Subject | Re: [External Email] Re: [PATCH v1 0/2] virtio-mmio: support multiple interrupt vectors |
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On Mon, Jul 22, 2019 at 4:39 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > On Mon, Jul 22, 2019 at 11:22:02AM +0800, 李菲 wrote: > > On Fri, Jul 19, 2019 at 11:14 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > > > > > On Fri, Jul 19, 2019 at 09:31:33PM +0800, Fei Li wrote: > > > > Hi, > > > > > > > > This patch series implements multiple interrupt vectors support for > > > > virtio-mmio device. This is especially useful for multiqueue vhost-net > > > > device when using firecracker micro-vms as the guest. > > > > > > > > Test result: > > > > With 8 vcpus & 8 net queues set, one vhost-net device with 8 irqs can > > > > receive 9 times more pps comparing with only one irq: > > > > - 564830.38 rxpck/s for 8 irqs on > > > > - 67665.06 rxpck/s for 1 irq on > > > > > > > > Please help to review, thanks! > > > > > > > > Have a nice day > > > > Fei > > > > > > > > > Interesting. The spec says though: > > > > > > 4.2.3.4 > > > Notifications From The Device > > > The memory mapped virtio device is using a single, dedicated interrupt signal, which is asserted when at > > > least one of the bits described in the description of InterruptStatus is set. This is how the device sends a > > > used buffer notification or a configuration change notification to the device. > > > > > Yes, the spec needs to be updated if we want to use mult-irqs. > > > > > > So I'm guessing we need to change the host/guest interface? > > Just to confirm, does the "the host/guest interface" you mentioned mean how to > > pass the irq information from the user space tool to guest kernel? > > In this patch, we do this by passing the [irq_start, irq_end] > > interface via setting guest > > kernel command line, that is done in vm_cmdline_set(). > > Also there is another way to do this: add two new registers describing irq info > > (irq_start & irq_end OR irq_start & irq_numbers) to the virtio config space. > > > > Which one do you prefer? > > I'm not sure - so far irq was passed on the command line, right? Yes. > > The first step in implementing any spec change would be to update qemu > code to virtio 1. Which is not a huge project but so far no one > bothered. Emm, actually I only did the test with using firecracker to start a micro-vm, but without qemu. To be honest, the reason why implementing multi-irq on virtio-mmio is mainly because the current firecracker using virtio-mmio device and it has no pci thing, thus no msi/msix to handle the interruptions. On the other hand, considering pci is well supported in qemu, I am wondering whether we still need this. If needed, we would like to do this. :)
Have a nice day, thanks Fei > > > > > If true pls cc virtio-dev. > > Sure. > > > > > > Also, do we need to update dt bindings documentation? > > You mean the following doc? Sure. :) > > https://github.com/torvalds/linux/blob/master/Documentation/devicetree/bindings/virtio/mmio.txt > > > > Thanks for the review! > > > > Have a nice day > > Fei > > > > > > > > > > > > > > > Fam Zheng (1): > > > > virtio-mmio: Process vrings more proactively > > > > > > > > Fei Li (1): > > > > virtio-mmio: support multiple interrupt vectors > > > > > > > > drivers/virtio/virtio_mmio.c | 238 +++++++++++++++++++++++++++++++++++-------- > > > > 1 file changed, 196 insertions(+), 42 deletions(-) > > > > > > > > -- > > > > 2.11.0
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