> Looks good, thanks! Yet something to improve, see below:
> > ---
> > v2:
> > - Add the last 2 points to the patch.
> > - Rephrase the "commands are best-effort" note.
> > - Replace "notification" with "used buffer notification" to be
> > more consistent.
> > v3:
> > - Add an intro explaining the entire coalescing operation.
> > v4:
> > - Minor wording fixes.
> > - Rephrase the general note.
> > v5:
> > - Replace virtio_net_ctrl_coal->usecs with
> > virtio_net_ctrl_coal->max_usecs
> >
> > device-types/net/description.tex | 69 +++++++++++++++++++-------------
> > 1 file changed, 41 insertions(+), 28 deletions(-)
> >
> > diff --git a/device-types/net/description.tex
> > b/device-types/net/description.tex
> > index 1741c79..a4cff05 100644
> > --- a/device-types/net/description.tex
> > +++ b/device-types/net/description.tex
> > @@ -1514,15 +1514,15 @@ \subsubsection{Control Virtqueue}\label{sec:Device
> > Types / Network Device / Devi
> > If the VIRTIO_NET_F_NOTF_COAL feature is negotiated, the driver can
> > send control commands for dynamically changing the coalescing parameters.
> >
> > -\begin{lstlisting}
> > -struct virtio_net_ctrl_coal_rx {
> > - le32 rx_max_packets;
> > - le32 rx_usecs;
> > -};
> > +\begin{note}
> > +The behavior of the device in response to these commands is best-effort:
> > +the device may generate notifications more or less frequently than
> > specified.
> > +\end{note}
> >
> > -struct virtio_net_ctrl_coal_tx {
> > - le32 tx_max_packets;
> > - le32 tx_usecs;
> > +\begin{lstlisting}
> > +struct virtio_net_ctrl_coal {
> > + le32 max_packets;
> > + le32 max_usecs;
> > };
> >
> > #define VIRTIO_NET_CTRL_NOTF_COAL 6
> > @@ -1532,49 +1532,62 @@ \subsubsection{Control Virtqueue}\label{sec:Device
> > Types / Network Device / Devi
> >
> > Coalescing parameters:
> > \begin{itemize}
> > -\item \field{rx_usecs}: Maximum number of usecs to delay a RX notification.
> > -\item \field{tx_usecs}: Maximum number of usecs to delay a TX notification.
> > -\item \field{rx_max_packets}: Maximum number of packets to receive before
> > a RX notification.
> > -\item \field{tx_max_packets}: Maximum number of packets to send before a
> > TX notification.
> > +\item \field{max_usecs} for RX: Maximum number of usecs to delay a RX
> > notification.
> > +\item \field{max_usecs} for TX: Maximum number of usecs to delay a TX
> > notification.
>
> we really should not abbreviate the description (field name is ok). usecs to
> delay -> microseconds
> to delay, right? same elsewhere.
>
Good point, thanks.
> > +\item \field{max_packets} for RX: Maximum number of packets to receive
> > before a RX notification.
> > +\item \field{max_packets} for TX: Maximum number of packets to send before
> > a TX notification.
> > \end{itemize}
> >
> > -
> > The class VIRTIO_NET_CTRL_NOTF_COAL has 2 commands:
> > \begin{enumerate}
> > -\item VIRTIO_NET_CTRL_NOTF_COAL_TX_SET: set the \field{tx_usecs} and
> > \field{tx_max_packets} parameters.
> > -\item VIRTIO_NET_CTRL_NOTF_COAL_RX_SET: set the \field{rx_usecs} and
> > \field{rx_max_packets} parameters.
> > +\item VIRTIO_NET_CTRL_NOTF_COAL_TX_SET: set the \field{max_usecs} and
> > \field{max_packets} parameters for all the transmit virtqueues.
> > +\item VIRTIO_NET_CTRL_NOTF_COAL_RX_SET: set the \field{max_usecs} and
> > \field{max_packets} parameters for all the receive virtqueues.
> > \end{enumerate}
> >
> > -\subparagraph{RX Notifications}\label{sec:Device Types / Network Device /
> > Device Operation / Control Virtqueue / Notifications Coalescing / RX
> > Notifications}
> > +\subparagraph{Operation}\label{sec:Device Types / Network Device / Device
> > Operation / Control Virtqueue / Notifications Coalescing / Operation}
> > +
> > +The device sends a used buffer notification once the notification
> > conditions are met, if the notifications are not suppressed as explained in
> > \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Used Buffer
> > Notification Suppression}.
> > +
> > +When the device has non-zero \field{max_usecs} and non-zero
> > \field{max_packets}, it starts counting usecs and packets upon
> > receiving/sending a packet.
> > +The device counts packets and usecs for each receive virtqueue and
> > transmit virtqueue separately.
> > +In this case, the notification conditions are met when \field{max_usecs}
> > usecs elapses, or upon sending/receiving \field{max_packets} packets,
> > whichever happens first.
>
> and should we maybe add: "both the timer and the packet counter then
> reset until the next packet"?
>
I didn't include the "device should reset the counters" part in the
first place thinking that a device may implement the mechanism
differently.
For example, a device may have a variable holding the next usecs value
to trigger a notification, and a free running counter.
Maybe
"... whichever happens first.
After the notification conditions are met, the device waits for the
next packet and starts counting again."
I don't really mind, If you think that the device implementation is
not essential here and we should add your suggestion, I'm ok with
that.
> > +
> > +When the device has \field{max_usecs} = 0 or \field{max_packets} = 0, the
> > notification conditions are met after every packet received/sent.
> > +
> > +\subparagraph{RX Example}\label{sec:Device Types / Network Device / Device
> > Operation / Control Virtqueue / Notifications Coalescing / RX Example}
> >
> > If, for example:
> > \begin{itemize}
> > -\item \field{rx_usecs} = 10.
> > -\item \field{rx_max_packets} = 15.
> > +\item \field{max_usecs} = 10.
> > +\item \field{max_packets} = 15.
> > \end{itemize}
> > -
>
> in fact the below is true for each queue separately even for an MQ device
> right? So I feel it's helpful if we include this in the example too. S:
>
> > -The device will operate as follows:
> > -
> > +then a device with a single receive virtqueue will operate as follows:
>
> we could make it e.g. s/a device/each receive virtqueue of a device/
>
>
> > \begin{itemize}
> > \item The device will count received packets until it accumulates 15, or
> > until 10 usecs elapsed since the first one was received.
>
> s/received packets/packets received on each virtqueue/
>
>
Good points, thanks.
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