Re: [virtio-comment] [PATCH] Introduction of Virtio Network device interrupt coalescing feature

[Stefan Hajnoczi <stefanha@redhat.com>]

On Thu, May 12, 2022 at 11:07:39AM +0300, Alvaro Karsz wrote:
> Control a network device interrupt coalescing parameters using the control virtqueue.
> A new control class was added: VIRTIO_NET_CTRL_INTR_COAL.
> 
> This class provides 2 commands:
> - VIRTIO_NET_CTRL_INTR_COAL_USECS_SET:
>   Ask the network device to change the rx-usecs and tx-usecs parameters.
>   rx-usecs - Time to delay an RX interrupt after packet arrival in microseconds.
>   tx-usecs - Time to delay a TX interrupt after a sending a packet in microseconds.
> 
> - VIRTIO_NET_CTRL_INTR_COAL_FRAMES_SET:
>   Ask the network device to change the rx-max-frames and tx-max-frames parameters.
>   rx-max-frames - Number of packets to delay an RX interrupt after packet arrival.
>   tx-max-frames - Number of packets to delay a TX interrupt after sending a packet.
> 
> 
> Signed-off-by: Alvaro Karsz <alvaro.karsz@solid-run.com>
> ---
>  content.tex | 41 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)

Please add a sentence about how this interacts with Used Buffer
Notification Suppression. My guess is that suppression takes effect in
addition to virtio-net-specific coalescing, so it's possible that the
notification will be suppressed even after the timer expires or frame
count is exceeded?

Also, since the VIRTIO specification usually talks about Notifications
instead of "interrupts" (see 2.3 Notifications) I think it makes sense
to use that terminology instead of "interrupts". Interrupts are more of
transport-level (e.g. PCI, MMIO) concept than a VIRTIO device model
concept.

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