After another inspection, I found some typos in the patch, will be
fixed in the next version.
>
> This patch adds a new feature, VIRTIO_NET_F_NOTF_COAL_LOW_HIGH, while
> clarifying/fixing existing coalescing concepts.
>
> The new feature adds 4 new commands to VIRTIO_NET_CTRL_NOTF_COAL class:
> - VIRTIO_NET_CTRL_NOTF_COAL_LOW_TX_SET - coalescing parameters
> to use when the packet rate is equal or lower then the low
> threshold for TX.
s/then/than/
> - VIRTIO_NET_CTRL_NOTF_COAL_LOW_RX_SET - coalescing parameters
> to use when the packet rate is equal or lower then the low
> threshold for RX.
s/then/than/
> - VIRTIO_NET_CTRL_NOTF_COAL_HIGH_TX_SET - coalescing parameters
> to use when the packet rate is equal or higher then the high
> threshold for TX.
s/then/than/
> - VIRTIO_NET_CTRL_NOTF_COAL_HIGH_RX_SET - coalescing parameters
> to use when the packet rate is equal or higher then the high
> threshold for RX.
s/then/than/
> On top of the new feature, this patch:
> - Unifies the virtio_net_ctrl_coal structs, since the one for tx
> and the one for rx are identical.
> - Clarifies that the coalescing commands are best-effort.
> - Specifies coalescing in respect to delivering interrupts when config
> changes.
>
> Signed-off-by: Alvaro Karsz <alvaro.ka...@solid-run.com>
> ---
> v2:
> - Remove the "set of coalescing parameters" concept, use
> "coalescing parameters" instead.
> - Unify struct virtio_net_ctrl_coal_rx and strcut
> virtio_net_ctrl_coal_tx
s/strcut/struct
> to struct virtio_net_ctrl_coal.
> - Separate the commands to tx and rx, so devices could have
> different low/high rate coalescing parameters for tx and rx.
> - Unify struct virtio_net_ctrl_coal_high and struct
> virtio_net_ctrl_coal_low to struct virtio_net_ctrl_coal_threshold.
> - Clarify that the packet rate is in packet per second units.
> - Clarify that any notification coalescing command is best-effort.
> - Specify coalescing in respect to delivering interrupts when config
> changes.
> ---
> content.tex | 105 +++++++++++++++++++++++++++++++++++++++++++---------
> 1 file changed, 87 insertions(+), 18 deletions(-)
>
> diff --git a/content.tex b/content.tex
> index 96f4723..82b2597 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -3088,6 +3088,8 @@ \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_NOTF_COAL_LOW_HIGH(50)] Device supports notifications
> coalescing low rate and high rate sets.
> +
Replace with: Device supports low/high packet rate coalescing parameters.
> \item[VIRTIO_NET_F_NOTF_COAL(53)] Device supports notifications coalescing.
>
> \item[VIRTIO_NET_F_GUEST_USO4 (54)] Driver can receive USOv4 packets.
> @@ -3142,6 +3144,7 @@ \subsubsection{Feature bit
> requirements}\label{sec:Device Types / Network Device
> \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_NOTF_COAL] Requires VIRTIO_NET_F_CTRL_VQ.
> +\item[VIRTIO_NET_F_NOTF_COAL_LOW_HIGH] Requires VIRTIO_NET_F_NOTF_COAL.
> \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}
> @@ -4493,43 +4496,62 @@ \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.
>
> +Note: In general, these commands are best-effort: A device could send a
> notification even if it is not supposed to.
> +
> \begin{lstlisting}
> -struct virtio_net_ctrl_coal_rx {
> - le32 rx_max_packets;
> - le32 rx_usecs;
> +struct virtio_net_ctrl_coal {
> + le32 max_packets;
> + le32 usecs;
> };
>
> -struct virtio_net_ctrl_coal_tx {
> - le32 tx_max_packets;
> - le32 tx_usecs;
> +struct virtio_net_ctrl_coal_threshold {
> + le32 pkt_rate;
> + struct virtio_net_ctrl_coal params;
> };
>
> #define VIRTIO_NET_CTRL_NOTF_COAL 6
> #define VIRTIO_NET_CTRL_NOTF_COAL_TX_SET 0
> #define VIRTIO_NET_CTRL_NOTF_COAL_RX_SET 1
> + #define VIRTIO_NET_CTRL_NOTF_COAL_LOW_TX_SET 2 //Only if
> VIRTIO_NET_F_NOTF_COAL_LOW_HIGH negotiated
> + #define VIRTIO_NET_CTRL_NOTF_COAL_LOW_RX_SET 3 //Only if
> VIRTIO_NET_F_NOTF_COAL_LOW_HIGH negotiated
> + #define VIRTIO_NET_CTRL_NOTF_COAL_HIGH_TX_SET 4 //Only if
> VIRTIO_NET_F_NOTF_COAL_LOW_HIGH negotiated
> + #define VIRTIO_NET_CTRL_NOTF_COAL_HIGH_RX_SET 5 //Only if
> VIRTIO_NET_F_NOTF_COAL_LOW_HIGH negotiated
> \end{lstlisting}
>
> -Coalescing parameters:
> +TX Coalescing parameters:
> +\begin{itemize}
> +\item \field{usecs}: Maximum number of usecs to delay a TX notification.
> +\item \field{max_packets}: Maximum number of packets to send before a TX
> notification.
> +\end{itemize}
> +
> +RX Coalescing parameters:
> +\begin{itemize}
> +\item \field{usecs}: Maximum number of usecs to delay a RX notification.
> +\item \field{max_packets}: Maximum number of packets to receive before a RX
> notification.
> +\end{itemize}
> +
> +General 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{pkt_rate}: Threshold for low/high packet rate coalescing
> parameters, in units of packets per second.
> \end{itemize}
>
>
> -The class VIRTIO_NET_CTRL_NOTF_COAL has 2 commands:
> +The class VIRTIO_NET_CTRL_NOTF_COAL has 6 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{usecs} and
> \field{max_packets} coalescing parameters for TX.
> +\item VIRTIO_NET_CTRL_NOTF_COAL_RX_SET: set the \field{usecs} and
> \field{max_packets} coalescing parameters for RX.
> +\item VIRTIO_NET_CTRL_NOTF_COAL_LOW_TX_SET: set the \field{usecs} and
> \field{max_packets} coalescing parameters for packet rate of \field{pkt_rate}
> or lower, for TX.
> +\item VIRTIO_NET_CTRL_NOTF_COAL_LOW_RX_SET: set the \field{usecs} and
> \field{max_packets} coalescing parameters for packet rate of \field{pkt_rate}
> or lower, for RX.
> +\item VIRTIO_NET_CTRL_NOTF_COAL_HIGH_TX_SET: set the \field{usecs} and
> \field{max_packets} coalescing parameters for packet rate of \field{pkt_rate}
> or higher, for TX.
> +\item VIRTIO_NET_CTRL_NOTF_COAL_HIGH_RX_SET: set the \field{usecs} and
> \field{max_packets} coalescing parameters for packet rate of \field{pkt_rate}
> or higher, for RX.
> \end{enumerate}
>
> \subparagraph{RX Notifications}\label{sec:Device Types / Network Device /
> Device Operation / Control Virtqueue / Notifications Coalescing / RX
> Notifications}
>
> If, for example:
> \begin{itemize}
> -\item \field{rx_usecs} = 10.
> -\item \field{rx_max_packets} = 15.
> +\item \field{usecs} = 10.
> +\item \field{max_packets} = 15.
> \end{itemize}
>
> The device will operate as follows:
> @@ -4543,8 +4565,8 @@ \subsubsection{Control Virtqueue}\label{sec:Device
> Types / Network Device / Devi
>
> If, for example:
> \begin{itemize}
> -\item \field{tx_usecs} = 10.
> -\item \field{tx_max_packets} = 15.
> +\item \field{usecs} = 10.
> +\item \field{max_packets} = 15.
> \end{itemize}
>
> The device will operate as follows:
> @@ -4554,18 +4576,65 @@ \subsubsection{Control Virtqueue}\label{sec:Device
> Types / Network Device / Devi
> \item If the notifications are not suppressed by the driver, the device will
> send an used buffer notification, otherwise, the device will not send an used
> buffer notification as long as the notifications are suppressed.
> \end{itemize}
>
> +\subparagraph{Notifications When Coalescing Parameters
> Change}\label{sec:Device Types / Network Device / Device Operation / Control
> Virtqueue / Notifications Coalescing / Notifications When Coalescing
> Parameters Change}
> +
> +When a device changes the coalescing parameters, the device needs to check
> if the new parameters are met and issue a notification if so.
> +
> +For example, \field{max_packets} = 15 for TX.
> +
> +If the device sends 10 packets, then it receives a
> VIRTIO_NET_CTRL_NOTF_COAL_TX_SET command with \field{max_packets} = 8, the
> device needs to immediately send a TX notification, if the notifications are
> not suppressed by the driver.
> +
> +\subparagraph{Low/High Rate Notifications}\label{sec:Device Types / Network
> Device / Device Operation / Control Virtqueue / Notifications Coalescing /
> Low/High Rate Notifications}
> +
> +If the VIRTIO_NET_F_NOTF_COAL_LOW_HIGH feature is negotiated, the driver can
> send the following low/high rate coalescing commands to the device:
> +
> +\begin{itemize}
> +\item VIRTIO_NET_CTRL_NOTF_COAL_LOW_TX_SET.
> +\item VIRTIO_NET_CTRL_NOTF_COAL_LOW_RX_SET.
> +\item VIRTIO_NET_CTRL_NOTF_COAL_HIGH_TX_SET.
> +\item VIRTIO_NET_CTRL_NOTF_COAL_HIGH_RX_SET.
> +\end{itemize}
> +
> +For VIRTIO_NET_CTRL_NOTF_COAL_LOW_TX_SET and
> VIRTIO_NET_CTRL_NOTF_COAL_LOW_RX_SET, struct virtio_net_ctrl_coal_threshold
> specifies the coalescing parameters to use when the packet rate is
> \field{pkt_rate} or lower.
> +
> +For VIRTIO_NET_CTRL_NOTF_COAL_HIGH_TX_SET and
> VIRTIO_NET_CTRL_NOTF_COAL_HIGH_RX_SET, struct virtio_net_ctrl_coal_threshold
> specifies the coalescing parameters to use when the packet rate is
> \field{pkt_rate} or higher.
> +
> \drivernormative{\subparagraph}{Notifications Coalescing}{Device Types /
> Network Device / Device Operation / Control Virtqueue / Notifications
> Coalescing}
>
> If the VIRTIO_NET_F_NOTF_COAL feature has not been negotiated, the driver
> MUST NOT issue VIRTIO_NET_CTRL_NOTF_COAL commands.
>
> +If the VIRTIO_NET_F_NOTF_COAL_LOW_HIGH feature has not been negotiated, the
> driver MUST NOT issue low/high rate coalescing commands.
> +
> +The driver SHOULD issue a low/high rate coalescing command with
> \field{pkt_rate} 0 in order to remove the low/high rate coalescing parameters.
> +
> +The driver MUST NOT issue a VIRTIO_NET_CTRL_NOTF_COAL_LOW_TX_SET command
> with \field{pkt_rate} equal or higher than a \field{pkt_rate} previously sent
> with a VIRTIO_NET_CTRL_NOTF_COAL_HIGH_TX_SET command.
> +
> +The driver MUST NOT issue a VIRTIO_NET_CTRL_NOTF_COAL_LOW_RX_SET command
> with \field{pkt_rate} equal or higher than a \field{pkt_rate} previously sent
> with a VIRTIO_NET_CTRL_NOTF_COAL_HIGH_RX_SET command.
> +
> +The driver MUST NOT issue a VIRTIO_NET_CTRL_NOTF_COAL_HIGH_TX_SET command
> with \field{pkt_rate} equal or lower than a \field{pkt_rate} previously sent
> with a VIRTIO_NET_CTRL_NOTF_COAL_LOW_TX_SET command.
> +
> +The driver MUST NOT issue a VIRTIO_NET_CTRL_NOTF_COAL_HIGH_RX_SET command
> with \field{pkt_rate} equal or lower than a \field{pkt_rate} previously sent
> with a VIRTIO_NET_CTRL_NOTF_COAL_LOW_RX_SET command.
> +
> \devicenormative{\subparagraph}{Notifications Coalescing}{Device Types /
> Network Device / Device Operation / Control Virtqueue / Notifications
> Coalescing}
>
> A device SHOULD respond to the VIRTIO_NET_CTRL_NOTF_COAL commands with
> VIRTIO_NET_ERR if it was not able to change the parameters.
>
> A device SHOULD NOT send used buffer notifications to the driver, if the
> notifications are suppressed as explained in \ref{sec:Basic Facilities of a
> Virtio Device / Virtqueues / Used Buffer Notification Suppression}, even if
> the coalescing counters expired.
>
> +A device MUST remove the low/high rate coalescing parameters, if a low/high
> rate coalescing command is received with \field{pkt_rate} 0.
> +
> +A device MUST respond with VIRTIO_NET_ERR to a
> VIRTIO_NET_CTRL_NOTF_COAL_LOW_TX_SET command with \field{pkt_rate} equal or
> higher than a \field{pkt_rate} previously received with a
> VIRTIO_NET_CTRL_NOTF_COAL_HIGH_TX_SET command.
> +
> +A device MUST respond with VIRTIO_NET_ERR to a
> VIRTIO_NET_CTRL_NOTF_COAL_LOW_RX_SET command with \field{pkt_rate} equal or
> higher than a \field{pkt_rate} previously received with a
> VIRTIO_NET_CTRL_NOTF_COAL_HIGH_RX_SET command.
> +
> +A device MUST respond with VIRTIO_NET_ERR to a
> VIRTIO_NET_CTRL_NOTF_COAL_HIGH_TX_SET command with \field{pkt_rate} equal or
> lower than a \field{pkt_rate} previously received with a
> VIRTIO_NET_CTRL_NOTF_COAL_LOW_TX_SET command.
> +
> +A device MUST respond with VIRTIO_NET_ERR to a
> VIRTIO_NET_CTRL_NOTF_COAL_HIGH_RX_SET command with \field{pkt_rate} equal or
> lower than a \field{pkt_rate} previously received with a
> VIRTIO_NET_CTRL_NOTF_COAL_LOW_RX_SET command.
> +
> Upon reset, a device MUST initialize all coalescing parameters to 0.
>
> +Upon reset, a device MUST not have a low/high rate coalescing parameters.
> +
> \subsubsection{Legacy Interface: Framing Requirements}\label{sec:Device
> Types / Network Device / Legacy Interface: Framing Requirements}
>
> --
> 2.32.0
>
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