Jason Wang
2021-Mar-05 03:42 UTC
[RFC v4 10/11] vduse: Introduce a workqueue for irq injection
On 2021/3/5 11:30 ??, Yongji Xie wrote:> On Fri, Mar 5, 2021 at 11:05 AM Jason Wang <jasowang at redhat.com> wrote: >> >> On 2021/3/4 4:58 ??, Yongji Xie wrote: >>> On Thu, Mar 4, 2021 at 2:59 PM Jason Wang <jasowang at redhat.com> wrote: >>>> On 2021/2/23 7:50 ??, Xie Yongji wrote: >>>>> This patch introduces a workqueue to support injecting >>>>> virtqueue's interrupt asynchronously. This is mainly >>>>> for performance considerations which makes sure the push() >>>>> and pop() for used vring can be asynchronous. >>>> Do you have pref numbers for this patch? >>>> >>> No, I can do some tests for it if needed. >>> >>> Another problem is the VIRTIO_RING_F_EVENT_IDX feature will be useless >>> if we call irq callback in ioctl context. Something like: >>> >>> virtqueue_push(); >>> virtio_notify(); >>> ioctl() >>> ------------------------------------------------- >>> irq_cb() >>> virtqueue_get_buf() >>> >>> The used vring is always empty each time we call virtqueue_push() in >>> userspace. Not sure if it is what we expected. >> >> I'm not sure I get the issue. >> >> THe used ring should be filled by virtqueue_push() which is done by >> userspace before? >> > After userspace call virtqueue_push(), it always call virtio_notify() > immediately. In traditional VM (vhost-vdpa) cases, virtio_notify() > will inject an irq to VM and return, then vcpu thread will call > interrupt handler. But in container (virtio-vdpa) cases, > virtio_notify() will call interrupt handler directly. So it looks like > we have to optimize the virtio-vdpa cases. But one problem is we don't > know whether we are in the VM user case or container user case.Yes, but I still don't get why used ring is empty after the ioctl()? Used ring does not use bounce page so it should be visible to the kernel driver. What did I miss :) ? Thanks> > Thanks, > Yongji >