[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]
Subject: Re: [virtio-comment] [PATCH v10] virtio-net: support the virtqueue coalescing moderation
On Wednesday, 2023-03-01 at 22:10:27 +08, Heng Qi wrote: > Currently, coalescing parameters are grouped for all transmit and receive > virtqueues. This patch supports setting or getting the parameters for a > specified virtqueue, and a typical application of this function is netdim[1]. > > When the traffic between virtqueues is unbalanced, for example, one virtqueue > is busy and another virtqueue is idle, then it will be very useful to > control coalescing parameters at the virtqueue granularity. > > [1] https://docs.kernel.org/networking/net_dim.html > > Signed-off-by: Heng Qi <hengqi@linux.alibaba.com> > Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> > --- > This patch is on top of Alvaro's latest v7 patch: https://lists.oasis-open.org/archives/virtio-dev/202302/msg00431.html . > > v9->v10: > 1. Remove the "global values". @Parav Pandit > 2. Avoid multiple interpretations of command behavior. @Alvaro Karsz > > v8->v9: > 1. Declare the commands that can be sent for each feature. @Alvaro Karsz > 2. Add information about "global values" in the command's explanation. @Alvaro Karsz > > v7->v8: > 1. Use "best-effort" in Alvaro's patch instead of "the device may set the parameter to a value close to 2". @Michael S . Tsirkin, @David Edmondson > > v6->v7: > 1. Clarify the relationship of VIRTIO_NET_CTRL_NOTF_COAL_TX/RX_SET and VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET. @Alvaro Karsz, @Michael S. Tsirkin > 2. Remove the formula for vqn range. @Parav Pandit > 3. Some expressions are clearer. @Parav Pandit, @Michael S. Tsirkin > > v5->v6: > 1. Explain that the device may set a different value than the one passed in by the driver. @David Edmondson > > v4->v5: > 1. Add the correspondence between virtio_net_ctrl_coal and virtio_net_ctrl_coal_vq and control commands. @Michael S. Tsirkin > 2. Add read and write attributes for each field. @Michael S. Tsirkin > 3. A clearer description of how to set coalescing parameters for vq reset. @Michael S. Tsirkin > 4. Fix some syntax errors. @Michael S. Tsirkin, @David Edmondson > > v3->v4: > 1. Include virtio_net_ctrl_coal in the virtio_net_ctrl_coal_vq structure. @Alvaro Karsz > 2. Add consideration of vq reset. @Michael S. Tsirkin, @Parav Pandit, @Alvaro Karsz > 3. Avoid too many examples by giving a comprehensive example. @Michael S. Tsirkin > 4. Fix typos and streamline clarifications. @Michael S. Tsirkin, @Parav Pandit, @Alvaro Karsz > > v2->v3: > 1. Add the netdim link. @Parav Pandit > 2. VIRTIO_NET_F_VQ_NOTF_COAL no longer depends on VIRTIO_NET_F_NOTF_COAL. @Michael S. Tsirkin, @Alvaro Karsz > 3. _VQ_GET is explained more. @Michael S. Tsirkin > 4. Add more examples to avoid misunderstandings. @Michael S. Tsirkin > 5. Clarify some statements. @Michael S. Tsirkin, @Parav Pandit, @Alvaro Karsz > 6. Adjust the virtio_net_ctrl_coal_vq structure. @Michael S. Tsirkin > 7. Fix some typos. @Michael S. Tsirkin > > v1->v2: > 1. Rename VIRTIO_NET_F_PERQUEUE_NOTF_COAL to VIRTIO_NET_F_VQ_NOTF_COAL. @Michael S. Tsirkin > 2. Use the \field{vqn} instead of the qid. @Michael S. Tsirkin > 3. Unify tx and rx control structures into one structure virtio_net_ctrl_coal_vq. @Michael S. Tsirkin > 4. Add a new control command VIRTIO_NET_CTRL_NOTF_COAL_VQ. @Michael S. Tsirkin, @Parav Pandit, @Alvaro Karsz > 5. The special value 0xFFF is removed because VIRTIO_NET_CTRL_NOTF_COAL can be used. @Alvaro Karsz > 6. Clarify some special scenarios. @Michael S. Tsirkin, @Parav Pandit, @Alvaro Karsz > > device-types/net/description.tex | 88 ++++++++++++++++++++++++++++---- > 1 file changed, 77 insertions(+), 11 deletions(-) > > diff --git a/device-types/net/description.tex b/device-types/net/description.tex > index e71e33b..b5d45e8 100644 > --- a/device-types/net/description.tex > +++ b/device-types/net/description.tex > @@ -83,6 +83,8 @@ \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_VQ_NOTF_COAL(52)] Device supports virtqueue notification coalescing. > + > \item[VIRTIO_NET_F_NOTF_COAL(53)] Device supports notifications coalescing. > > \item[VIRTIO_NET_F_GUEST_USO4 (54)] Driver can receive USOv4 packets. > @@ -139,6 +141,7 @@ \subsubsection{Feature bit requirements}\label{sec:Device Types / Network Device > \item[VIRTIO_NET_F_NOTF_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. > +\item[VIRTIO_NET_F_VQ_NOTF_COAL] Requires VIRTIO_NET_F_CTRL_VQ. > \end{description} > > \subsubsection{Legacy Interface: Feature bits}\label{sec:Device Types / Network Device / Feature bits / Legacy Interface: Feature bits} > @@ -1505,13 +1508,13 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi > > \paragraph{Notifications Coalescing}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Notifications Coalescing} > > -If the VIRTIO_NET_F_NOTF_COAL feature is negotiated, the driver can > -send control commands for dynamically changing the coalescing parameters. > +If the VIRTIO_NET_F_NOTF_COAL feature is negotiated, a driver can send > +commands VIRTIO_NET_CTRL_NOTF_COAL_TX_SET and VIRTIO_NET_CTRL_NOTF_COAL_RX_SET > +for notification coalescing. "to change the notification coalescing parameters." > > -\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} > +If the VIRTIO_NET_F_VQ_NOTF_COAL feature is negotiated, a driver can send > +commands VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET and VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET > +for notification coalescing. "to change the per-virtqueue notification coalescing parameters." > > \begin{lstlisting} > struct virtio_net_ctrl_coal { > @@ -1519,25 +1522,74 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi > le32 max_usecs; > }; > > +struct virtio_net_ctrl_coal_vq { > + le16 vqn; > + le16 reserved; > + struct virtio_net_ctrl_coal coal; > +}; > + > #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_VQ_SET 2 > + #define VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET 3 > \end{lstlisting} > > Coalescing parameters: > \begin{itemize} > +\item \field{vqn}: The virtqueue number of an enabled transmit or receive virtqueue. > \item \field{max_usecs} for RX: Maximum number of microseconds to delay a RX notification. > \item \field{max_usecs} for TX: Maximum number of microseconds to delay a TX notification. > \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: > +\field{reserved} is reserved and it is ignored by a device. > + > +Read/Write attributes for coalescing parameters: > +\begin{itemize} > +\item For commands VIRTIO_NET_CTRL_NOTF_COAL_TX_SET and VIRTIO_NET_CTRL_NOTF_COAL_RX_SET, \field{max_usecs} > + and \field{max_packets} are write-only for a driver. > +\item For the command VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET, \field{vqn}, \field{reserved}, \field{max_usecs} > + and \field{max_packets} are write-only for a driver. > +\item For the command VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET, \field{vqn} and \field{reserved} are write-only > + for a driver, and, \field{max_usecs} and \field{max_packets} are read-only for the driver. > +\end{itemize} > + > +The class VIRTIO_NET_CTRL_NOTF_COAL has 4 commands: > \begin{enumerate} > -\item VIRTIO_NET_CTRL_NOTF_COAL_TX_SET: set the \field{max_usecs} and \field{max_packets} parameters for all transmit virtqueues. > -\item VIRTIO_NET_CTRL_NOTF_COAL_RX_SET: set the \field{max_usecs} and \field{max_packets} parameters for all receive virtqueues. > +\item VIRTIO_NET_CTRL_NOTF_COAL_TX_SET: use the structure virtio_net_ctrl_coal to set the \field{max_usecs} and \field{max_packets} parameters for all transmit virtqueues. > +\item VIRTIO_NET_CTRL_NOTF_COAL_RX_SET: use the structure virtio_net_ctrl_coal to set the \field{max_usecs} and \field{max_packets} parameters for all receive virtqueues. > +\item VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET: use the structure virtio_net_ctrl_coal_vq to set the \field{max_usecs} and \field{max_packets} parameters > + for an enabled transmit/receive virtqueue whose number is \field{vqn}. > +\item VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET: use the structure virtio_net_ctrl_coal_vq to get the \field{max_usecs} and \field{max_packets} parameters > + for an enabled transmit/receive virtqueue whose number is \field{vqn}. Should this now be "whose index is \field{vqn}"? > \end{enumerate} > > +\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} > + > +If coalescing parameters are being set, the device applies the last coalescing parameters received for a > +virtqueue, regardless of the command used to set the parameters. Use the following command sequence > +with 2 pairs of virtqueues as an example: > +Each of the following commands sets \field{max_usecs} and \field{max_packets} parameters for virtqueues. > +\begin{itemize} > +\item Command1: VIRTIO_NET_CTRL_NOTF_COAL_RX_SET sets coalescing parameters for virtqueue0 and virtqueue2, and, virtqueue1 and virtqueue3 retain their previous parameter values. > +\item Command2: VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET with \field{vqn} = 0 sets coalescing parameters for virtqueue0, and virtqueue2 retains the values from command1. > +\item Command3: VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET with \field{vqn} = 0, the device responds with coalescing parameters of virtqueue0 set by command2. > +\item Command4: VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET with \field{vqn} = 1 sets coalescing parameters for virtqueue1, and virtqueue3 retains its previous values. > +\item Command5: VIRTIO_NET_CTRL_NOTF_COAL_TX_SET sets coalescing parameters for virtqueue1 and virtqueue3, and overrides the values set by command4. > +\item Command6: VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET with \field{vqn} = 1, the device responds with coalescing parameters of virtqueue1 set by command5. > +\end{itemize} > + > +Upon disabling and re-enabling the transmit virtqueue, the device will set the coalescing parameters of the virtqueue > +to those configured through the VIRTIO_NET_CTRL_NOTF_COAL_TX_SET command, or to 0 if the command did not set any TX coalescing parameters. > + > +Upon disabling and re-enabling the receive virtqueue, the device will set the coalescing parameters of the virtqueue > +to those configured through the VIRTIO_NET_CTRL_NOTF_COAL_RX_SET command, or to 0 if the command did not set any RX coalescing parameters. > + > \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 and if the notifications are not suppressed as explained in \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Used Buffer Notification Suppression}. > @@ -1585,11 +1637,25 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi > > \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. > +A driver MUST negotiate the VIRTIO_NET_F_NOTF_COAL feature before issuing commands VIRTIO_NET_CTRL_NOTF_COAL_TX_SET and VIRIO_NET_CTRL_NOTF_COAL_RX_SET. > + > +A driver MUST negotiate the VIRTIO_NET_F_VQ_NOTF_COAL feature before issuing commands VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET and VIRIO_NET_CTRL_NOTF_COAL_VQ_GET. > + > +A driver MUST ignore the values of coalescing parameters received from the VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET command if a device responds with VIRTIO_NET_ERR. > > \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 MUST ignore \field{reserved}. > + > +A device SHOULD respond to VIRTIO_NET_CTRL_NOTF_COAL_TX_SET and VIRTIO_NET_CTRL_NOTF_COAL_RX_SET commands with VIRTIO_NET_ERR if it was not able to change the parameters. > + > +A device MUST respond to the VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET command with VIRTIO_NET_ERR if it was not able to change the parameters. > + > +A device MUST respond to VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET and VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET commands with VIRTIO_NET_ERR if the given virtqueue is disabled. > + > +After disabling and re-enabling a transmit/receive virtqueue, the device MUST set coalescing parameters of the virtqueue > +to those configured using the VIRTIO_NET_CTRL_NOTF_COAL_TX_SET/VIRTIO_NET_CTRL_NOTF_COAL_RX_SET command, or, if the command > +did not configure TX/RX coalescing parameters, to 0. > > A device SHOULD NOT send used buffer notifications to the driver if the notifications are suppressed, even if the notification conditions are met. -- Welcome to Conditioning.
[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]