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Subject: Re: [virtio-comment] [PATCH] Introduction of Virtio Network device interrupt coalescing feature
Hi,
Github issue was opened for this patch.
https://github.com/oasis-tcs/virtio-spec/issues/141
On Thu, May 12, 2022 at 2:19 PM Alvaro Karsz <alvaro.karsz@solid-run.com> wrote:
>
> Hi,
>
>> I would like to know what scenarios this function can be used in, what problems
>> can be solved or what benefits can be obtained?
>
>
> One example is using ethtool command to configure these parameters on a VirtIO network compatible device.
> You could use the following command on the host to adjust the interrupt coalescing parameters:
>
> $ ethtool -C <interface> tx-usecs X rx-usecs Y tx-frames Z rx-frames W
>
> I'm working on a Network compatible device which can coalesce interrupts, but there is no interface to adjust the usecs and frames parameters.
> Having this command would give an interface to change these parameters on runtime.
>
>
>
> On Thu, May 12, 2022 at 2:06 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
>>
>> On Thu, 12 May 2022 11:07:39 +0300, Alvaro Karsz <alvaro.karsz@solid-run.com> 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.
>> >
>>
>> I would like to know what scenarios this function can be used in, what problems
>> can be solved or what benefits can be obtained?
>>
>> Thanks.
>>
>> >
>> > Signed-off-by: Alvaro Karsz <alvaro.karsz@solid-run.com>
>> > ---
>> > content.tex | 41 +++++++++++++++++++++++++++++++++++++++++
>> > 1 file changed, 41 insertions(+)
>> >
>> > diff --git a/content.tex b/content.tex
>> > index 7508dd1..a70cb27 100644
>> > --- a/content.tex
>> > +++ b/content.tex
>> > @@ -3084,6 +3084,8 @@ \subsection{Feature bits}\label{sec:Device Types / Network Device / Feature bits
>> > \item[VIRTIO_NET_F_CTRL_MAC_ADDR(23)] Set MAC address through control
>> > channel.
>> >
>> > +\item[VIRTIO_NET_F_INTR_COAL(55)] Device supports interrupt coalescing.
>> > +
>> > \item[VIRTIO_NET_F_HOST_USO (56)] Device can receive USO packets. Unlike UFO
>> > (fragmenting the packet) the USO splits large UDP packet
>> > to several segments when each of these smaller packets has UDP header.
>> > @@ -3129,6 +3131,7 @@ \subsubsection{Feature bit requirements}\label{sec:Device Types / Network Device
>> > \item[VIRTIO_NET_F_GUEST_ANNOUNCE] Requires VIRTIO_NET_F_CTRL_VQ.
>> > \item[VIRTIO_NET_F_MQ] Requires VIRTIO_NET_F_CTRL_VQ.
>> > \item[VIRTIO_NET_F_CTRL_MAC_ADDR] Requires VIRTIO_NET_F_CTRL_VQ.
>> > +\item[VIRTIO_NET_F_INTR_COAL] Requires VIRTIO_NET_F_CTRL_VQ.
>> > \item[VIRTIO_NET_F_RSC_EXT] Requires VIRTIO_NET_F_HOST_TSO4 or VIRTIO_NET_F_HOST_TSO6.
>> > \item[VIRTIO_NET_F_RSS] Requires VIRTIO_NET_F_CTRL_VQ.
>> > \end{description}
>> > @@ -4464,6 +4467,44 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
>> > (necessarily when not using the legacy interface) little-endian.
>> >
>> >
>> > +\paragraph{Interrupt Coalescing}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Interrupt Coalescing}
>> > +
>> > +If the VIRTIO_NET_F_INTR_COAL feature is negotiated, the driver can
>> > +send control commands for dynamically changing the coalescing parameters.
>> > +
>> > +\begin{lstlisting}
>> > +struct virtio_net_ctrl_coal_usec {
>> > + le32 tx_usecs;
>> > + le32 rx_usecs;
>> > +};
>> > +
>> > +struct virtio_net_ctrl_coal_frames {
>> > + le32 tx_frames_max;
>> > + le32 rx_frames_max;
>> > +};
>> > +
>> > +#define VIRTIO_NET_CTRL_INTR_COAL 6
>> > + #define VIRTIO_NET_CTRL_INTR_COAL_USECS_SET 0
>> > + #define VIRTIO_NET_CTRL_INTR_COAL_FRAMES_SET 1
>> > +\end{lstlisting}
>> > +
>> > +The class VIRTIO_NET_CTRL_INTR_COAL has 2 commands:
>> > +\begin{itemize}
>> > +\item VIRTIO_NET_CTRL_INTR_COAL_USECS_SET: set the rx-usecs (time to delay an RX interrupt after packet arrival in microseconds) and tx-usecs (time to delay a TX interrupt after a sending a packet in microseconds) parameters.
>> > +\item VIRTIO_NET_CTRL_INTR_COAL_FRAMES_SET: set the rx-max-frames (number of packets to delay an RX interrupt after packet arrival) and tx-max-frames (number of packets to delay a TX interrupt after sending a packet) parameters.
>> > +\end{itemize}
>> > +
>> > +\drivernormative{\subparagraph}{Interrupt Coalescing}{Device Types / Network Device / Device Operation / Control Virtqueue / Interrupt Coalescing}
>> > +
>> > +
>> > +A driver MUST NOT send to the device VIRTIO_NET_CTRL_INTR_COAL commands if the VIRTIO_NET_F_INTR_COAL feature
>> > +has not been negotiated.
>> > +
>> > +\devicenormative{\subparagraph}{Interrupt Coalescing}{Device Types / Network Device / Device Operation / Control Virtqueue / Interrupt Coalescing}
>> > +
>> > +A device SHOULD respond to the VIRTIO_NET_CTRL_INTR_COAL commands with VIRTIO_NET_ERR if was not able to change the parameters.
>> > +
>> > +
>> > \subsubsection{Legacy Interface: Framing Requirements}\label{sec:Device
>> > Types / Network Device / Legacy Interface: Framing Requirements}
>> >
>> > --
>> > 2.32.0
>> >
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>> > OASIS Virtual I/O Device (VIRTIO) TC.
>> >
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>
>
>
> --
>
>
> Alvaro Karsz, Software
> +972-50-7696862| https://www.solid-run.com
--
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