On Fri, Mar 5, 2021 at 11:05 AM Jason Wang [off-list ref] wrote:

On 2021/3/4 4:58 下午, Yongji Xie wrote:

quoted

On Thu, Mar 4, 2021 at 2:59 PM Jason Wang [off-list ref] wrote:

quoted

On 2021/2/23 7:50 下午, Xie Yongji wrote:

quoted

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.

Thanks,
Yongji