[virtio-dev] Re: [virtio-comment] Re: [virtio-dev] Re: [PATCH v9] virtio-net: support the virtqueue coalescing moderation
在 2023/2/28 下午3:49, Michael S. Tsirkin 写道: On Tue, Feb 28, 2023 at 10:41:18AM +0800, Heng Qi wrote: The problem is the global qualifier. And it's not even global - there are two sets for rx and for tx and does not apply to cvq at all. How about "RX/TX coalescing parameters"? As Parav suggested, we probably don't need to mention "global values/coalescing parameters" since this values/parameters are the ones set by CTRL_NOTF_COAL_RX/TX_SET. Just like this: " After disabling and re-enabling a virtuqueue, the device MUST revert to coalescing parameters to the one configured using VIRTIO_NET_CTRL_NOTF_COAL. " Thanks. VIRTIO_NET_CTRL_NOTF_COAL is not a thing. Let's wait for Alvaro's new patch to be merged though, see what teminology he comes up with and reuse. Ok, are you referring to Alvaro's "virtio-net: Fix and update VIRTIO_NET_F_NOTF_COAL feature", if so I see that his v7 version is stable and has been voted in https://github.com/oasis-tcs/ virtio-spec/issues/159 , this patch was made on top of his v7 version. Thanks. - To unsubscribe, e-mail: virtio-dev-unsubscr...@lists.oasis-open.org For additional commands, e-mail: virtio-dev-h...@lists.oasis-open.org
Re: [virtio-dev] Re: [PATCH v9] virtio-net: support the virtqueue coalescing moderation
On Tue, Feb 28, 2023 at 10:41:18AM +0800, Heng Qi wrote: > > The problem is the global qualifier. And it's not even global - > > there are two sets for rx and for tx and does not apply to cvq at all. > > How about "RX/TX coalescing parameters"? > > As Parav suggested, we probably don't need to mention "global > values/coalescing parameters" since this values/parameters are the ones set > by CTRL_NOTF_COAL_RX/TX_SET. > > Just like this: > " > After disabling and re-enabling a virtuqueue, the device MUST revert to > coalescing parameters to the one configured using VIRTIO_NET_CTRL_NOTF_COAL. > " > > Thanks. VIRTIO_NET_CTRL_NOTF_COAL is not a thing. Let's wait for Alvaro's new patch to be merged though, see what teminology he comes up with and reuse. -- MST - To unsubscribe, e-mail: virtio-dev-unsubscr...@lists.oasis-open.org For additional commands, e-mail: virtio-dev-h...@lists.oasis-open.org
[virtio-dev] Re: [PATCH v9] virtio-net: support the virtqueue coalescing moderation
On Tue, Feb 28, 2023 at 01:40:29AM +, Parav Pandit wrote:
>
> > From: Heng Qi
> > Sent: Sunday, February 26, 2023 4:37 AM
>
> > +# Read/Write attributes for coalescing parameters \begin{itemize} \item
> Hash # above is not needed. Please remove.
>
> > +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}
> Instead of describing each individual fields of the structure struct
> virtio_net_ctrl_coal coal as read-only or write-only, better to say the
> struct itself as read/write only.
I don't see how you can reasonably do this. Which fields are RO and
which WO depends on the command.
> This way when/if in the future, if struct virtio_net_ctrl_coal coal extends,
> no need to rewrite this section of the spec.
Exactly the reverse.
If you specify RO/WO for each field then you don't need to touch
existing description when adding fields.
If you write in one place that all of struct is RO, when you add
WO fields you need to change it.
> > +
> > 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.
> > +
> > +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: set the \field{max_usecs} and
> > \field{max_packets} parameters for all transmit virtqueues, and values of
> > +coalescing parameters are recorded
> > as TX global values
> > by a device.
> "recording TX global values" is not conveying anything more as "all transmit
> virtqueues" is already mentioned.
> The original text without "recorded as Tx global values" is just fine. Same
> for the RX below.
I agree.
> > +\item VIRTIO_NET_CTRL_NOTF_COAL_RX_SET: set the \field{max_usecs} and
> > \field{max_packets} parameters for all receive virtqueues, and values of
> > +coalescing parameters are recorded
> > as RX global values
> > by a device.
> > +\item VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET: set the \field{max_usecs} and
> > \field{max_packets} parameters for an enabled transmit/receive
> > +virtqueue whose number is
> > \field{vqn}, and do not
> > change the TX/RX global values.
> > +\item VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET: the device returns the
> > \field{max_usecs} and \field{max_packets} parameters for an enabled
> > +transmit/receive virtqueue whose
> > number is \field{vqn}.
> > \end{enumerate}
> >
> > +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. For example with 2 pairs of virtqueues:
> > +# Command sequence
> > +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:
Re: [virtio-dev] Re: [PATCH v9] virtio-net: support the virtqueue coalescing moderation
在 2023/2/28 上午4:19, Michael S. Tsirkin 写道:
On Mon, Feb 27, 2023 at 08:45:43PM +0200, Alvaro Karsz wrote:
-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, the driver can send the
VIRTIO_NET_CTRL_NOTF_COAL_TX_SET
+and VIRTIO_NET_CTRL_NOTF_COAL_RX_SET commands to dynamically change the
coalescing parameters for all transmit
+and receive virtqueues, respectively.
+
+If the VIRTIO_NET_F_VQ_NOTF_COAL feature is negotiated:
+\begin{itemize}
+\item a driver can send a VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET command to set
coalescing parameters of a given
+ enabled transmit/receive virtqueue.
+\item a driver can send a VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET command to a
device, and the device responds with
+ coalescing parameters of a given enabled transmit/receive virtqueue.
+\end{itemize}
The VQ_NOTF_COAL commands are enclosed in an itemize and the NOTF_COAL
commands aren't.
I think that we should be consistent here.
The VQ commands are enclosed in an itemize because it has both GET and
SET operations.
I don't think VIRTIO_NET_CTRL_NOTF_COAL_RX_SET and
VIRTIO_NET_CTRL_NOTF_COAL_TX_SET
have to do this, because they are both settings, just in different
directions, and we have described them like this elsewhere.
I'm not sure that describing the commands in here is necessary, maybe
just mentioning which commands can be used with which feature bit is
Isn't that what this sentence does?
Yes, but it also describes what the command does
"to dynamically change the coalescing parameters for all transmit and
receive virtqueues"
Seems a bit repetitive to me.
enough (this is what I meant in v8, sorry if I wasn't clear).
I'm not saying that describing the commands in here is not good, but
notice that the commands are described in 3 different places.
Three places describe different effects.
#1 describes which commands are available for which feature.
#2 describes which command can use which structure.
#3 describes which parameters can be set for each command, and whether
they can affect "global values".
It is placed in the "Operation" section because it explains how the
device should behave.
You're right, but some parts seems repetitive to me:
#1: "commands to dynamically change the coalescing parameters for all
transmit and receive virtqueues"
#2: "commands use the virtio_net_ctrl_coal structure to set
\field{max_usecs} and \field{max_packets} for all transmit/receive
virtqueues."
#3: " set the \field{max_usecs} and \field{max_packets} parameters for
all transmit virtqueues, and values of..."
Feels like every time we re-explain the commands with more detail.
So, for example we read #2 and understand what the command does (set
usecs and packets), then we read #3 and understand that it does some
more stuff.
IMO we need to explain it once, with all the details.
This is how we've written it historically. The idea is that
reader can get everything on the first pass: 1st high level
picture then detailed description then the formalities.
Other specs do it differently so one has to re-read them
many times to understand. I don't like this personally and
I much prefer the virtio way.
Maybe #1 and #2 descriptions can be combined and described together.
This is #1.
\begin{note}
The behavior of the device in response to these commands is best-effort:
@@ -1519,25 +1531,76 @@ \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}
+The VIRTIO_NET_CTRL_NOTF_COAL_TX_SET and VIRTIO_NET_CTRL_NOTF_COAL_RX_SET
commands use the
+virtio_net_ctrl_coal structure to set \field{max_usecs} and
\field{max_packets} for all
+transmit/receive virtqueues.
+
+The VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET command uses the virtio_net_ctrl_coal_vq
structure
+to set \field{max_usecs} and \field{max_packets} for the supplied virtqueue
number \field{vqn}.
+
+The VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET command gets the values of
\field{max_usecs} and
+\field{max_packets} of the specified virtqueue from the device by setting
\field{vqn}
+in the virtio_net_ctrl_coal_vq structure.
+
This is #2.
+# 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
[virtio-dev] RE: [PATCH v9] virtio-net: support the virtqueue coalescing moderation
> From: Heng Qi
> Sent: Sunday, February 26, 2023 4:37 AM
> +# Read/Write attributes for coalescing parameters \begin{itemize} \item
Hash # above is not needed. Please remove.
> +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}
Instead of describing each individual fields of the structure struct
virtio_net_ctrl_coal coal as read-only or write-only, better to say the struct
itself as read/write only.
This way when/if in the future, if struct virtio_net_ctrl_coal coal extends, no
need to rewrite this section of the spec.
> +
> 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.
> +
> +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: set the \field{max_usecs} and
> \field{max_packets} parameters for all transmit virtqueues, and values of
> +coalescing parameters are recorded
> as TX global values
> by a device.
"recording TX global values" is not conveying anything more as "all transmit
virtqueues" is already mentioned.
The original text without "recorded as Tx global values" is just fine. Same for
the RX below.
> +\item VIRTIO_NET_CTRL_NOTF_COAL_RX_SET: set the \field{max_usecs} and
> \field{max_packets} parameters for all receive virtqueues, and values of
> +coalescing parameters are recorded
> as RX global values
> by a device.
> +\item VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET: set the \field{max_usecs} and
> \field{max_packets} parameters for an enabled transmit/receive
> +virtqueue whose number is
> \field{vqn}, and do not
> change the TX/RX global values.
> +\item VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET: the device returns the
> \field{max_usecs} and \field{max_packets} parameters for an enabled
> +transmit/receive virtqueue whose
> number is \field{vqn}.
> \end{enumerate}
>
> +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. For example with 2 pairs of virtqueues:
> +# Command sequence
> +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}
> +
> \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
Re: [virtio-dev] Re: [PATCH v9] virtio-net: support the virtqueue coalescing moderation
> > I see your point, but a reader will see the "global notifications > > coalescing parameter" concept, and won't know what it is until next > > paragraph. > > Maybe we can have a new list with the notification coalescing concepts > > (like the notification coalescing parameters)? Just throwing an idea > > here. > > Actually, "global notification coalescing parameters" is confusing: > are these global notifications? global coalescings? global parameters? > > The problem is the global qualifier. And it's not even global - > there are two sets for rx and for tx and does not apply to cvq at all. > How about "RX/TX coalescing parameters"? Seems fine to me. - To unsubscribe, e-mail: virtio-dev-unsubscr...@lists.oasis-open.org For additional commands, e-mail: virtio-dev-h...@lists.oasis-open.org
Re: [virtio-dev] Re: [PATCH v9] virtio-net: support the virtqueue coalescing moderation
On Mon, Feb 27, 2023 at 08:45:43PM +0200, Alvaro Karsz wrote:
> > >> -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, the driver can
> > >> send the VIRTIO_NET_CTRL_NOTF_COAL_TX_SET
> > >> +and VIRTIO_NET_CTRL_NOTF_COAL_RX_SET commands to dynamically change the
> > >> coalescing parameters for all transmit
> > >> +and receive virtqueues, respectively.
> > >> +
> > >> +If the VIRTIO_NET_F_VQ_NOTF_COAL feature is negotiated:
> > >> +\begin{itemize}
> > >> +\item a driver can send a VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET command to
> > >> set coalescing parameters of a given
> > >> + enabled transmit/receive virtqueue.
> > >> +\item a driver can send a VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET command to a
> > >> device, and the device responds with
> > >> + coalescing parameters of a given enabled transmit/receive
> > >> virtqueue.
> > >> +\end{itemize}
> > >>
> > > The VQ_NOTF_COAL commands are enclosed in an itemize and the NOTF_COAL
> > > commands aren't.
> > > I think that we should be consistent here.
> >
> > The VQ commands are enclosed in an itemize because it has both GET and
> > SET operations.
> >
> > I don't think VIRTIO_NET_CTRL_NOTF_COAL_RX_SET and
> > VIRTIO_NET_CTRL_NOTF_COAL_TX_SET
> > have to do this, because they are both settings, just in different
> > directions, and we have described them like this elsewhere.
> >
> > >
> > > I'm not sure that describing the commands in here is necessary, maybe
> > > just mentioning which commands can be used with which feature bit is
> >
> > Isn't that what this sentence does?
> >
>
> Yes, but it also describes what the command does
> "to dynamically change the coalescing parameters for all transmit and
> receive virtqueues"
>
> Seems a bit repetitive to me.
>
> > > enough (this is what I meant in v8, sorry if I wasn't clear).
> > >
> > > I'm not saying that describing the commands in here is not good, but
> > > notice that the commands are described in 3 different places.
> >
> > Three places describe different effects.
> >
> > #1 describes which commands are available for which feature.
> > #2 describes which command can use which structure.
> > #3 describes which parameters can be set for each command, and whether
> > they can affect "global values".
> > It is placed in the "Operation" section because it explains how the
> > device should behave.
> >
>
> You're right, but some parts seems repetitive to me:
> #1: "commands to dynamically change the coalescing parameters for all
> transmit and receive virtqueues"
>
> #2: "commands use the virtio_net_ctrl_coal structure to set
> \field{max_usecs} and \field{max_packets} for all transmit/receive
> virtqueues."
>
> #3: " set the \field{max_usecs} and \field{max_packets} parameters for
> all transmit virtqueues, and values of..."
>
> Feels like every time we re-explain the commands with more detail.
> So, for example we read #2 and understand what the command does (set
> usecs and packets), then we read #3 and understand that it does some
> more stuff.
>
> IMO we need to explain it once, with all the details.
This is how we've written it historically. The idea is that
reader can get everything on the first pass: 1st high level
picture then detailed description then the formalities.
Other specs do it differently so one has to re-read them
many times to understand. I don't like this personally and
I much prefer the virtio way.
> > Maybe #1 and #2 descriptions can be combined and described together.
> >
> > > This is #1.
> > >
> > >> \begin{note}
> > >> The behavior of the device in response to these commands is
> > >> best-effort:
> > >> @@ -1519,25 +1531,76 @@ \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}
> > >>
> > >> +The VIRTIO_NET_CTRL_NOTF_COAL_TX_SET and
> > >> VIRTIO_NET_CTRL_NOTF_COAL_RX_SET commands use the
> > >> +virtio_net_ctrl_coal structure to set \field{max_usecs} and
> > >> \field{max_packets} for all
> > >> +transmit/receive virtqueues.
> > >> +
> > >> +The VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET command uses the
> > >> virtio_net_ctrl_coal_vq structure
> > >> +to set \field{max_usecs} and \field{max_packets} for the supplied
> > >> virtqueue number \field{vqn}.
> > >> +
> > >> +The VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET command gets the values of
> > >> \field{max_usecs} and
> > >>
Re: [virtio-dev] Re: [PATCH v9] virtio-net: support the virtqueue coalescing moderation
> >> -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, the driver can send
> >> the VIRTIO_NET_CTRL_NOTF_COAL_TX_SET
> >> +and VIRTIO_NET_CTRL_NOTF_COAL_RX_SET commands to dynamically change the
> >> coalescing parameters for all transmit
> >> +and receive virtqueues, respectively.
> >> +
> >> +If the VIRTIO_NET_F_VQ_NOTF_COAL feature is negotiated:
> >> +\begin{itemize}
> >> +\item a driver can send a VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET command to set
> >> coalescing parameters of a given
> >> + enabled transmit/receive virtqueue.
> >> +\item a driver can send a VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET command to a
> >> device, and the device responds with
> >> + coalescing parameters of a given enabled transmit/receive virtqueue.
> >> +\end{itemize}
> >>
> > The VQ_NOTF_COAL commands are enclosed in an itemize and the NOTF_COAL
> > commands aren't.
> > I think that we should be consistent here.
>
> The VQ commands are enclosed in an itemize because it has both GET and
> SET operations.
>
> I don't think VIRTIO_NET_CTRL_NOTF_COAL_RX_SET and
> VIRTIO_NET_CTRL_NOTF_COAL_TX_SET
> have to do this, because they are both settings, just in different
> directions, and we have described them like this elsewhere.
>
> >
> > I'm not sure that describing the commands in here is necessary, maybe
> > just mentioning which commands can be used with which feature bit is
>
> Isn't that what this sentence does?
>
Yes, but it also describes what the command does
"to dynamically change the coalescing parameters for all transmit and
receive virtqueues"
Seems a bit repetitive to me.
> > enough (this is what I meant in v8, sorry if I wasn't clear).
> >
> > I'm not saying that describing the commands in here is not good, but
> > notice that the commands are described in 3 different places.
>
> Three places describe different effects.
>
> #1 describes which commands are available for which feature.
> #2 describes which command can use which structure.
> #3 describes which parameters can be set for each command, and whether
> they can affect "global values".
> It is placed in the "Operation" section because it explains how the
> device should behave.
>
You're right, but some parts seems repetitive to me:
#1: "commands to dynamically change the coalescing parameters for all
transmit and receive virtqueues"
#2: "commands use the virtio_net_ctrl_coal structure to set
\field{max_usecs} and \field{max_packets} for all transmit/receive
virtqueues."
#3: " set the \field{max_usecs} and \field{max_packets} parameters for
all transmit virtqueues, and values of..."
Feels like every time we re-explain the commands with more detail.
So, for example we read #2 and understand what the command does (set
usecs and packets), then we read #3 and understand that it does some
more stuff.
IMO we need to explain it once, with all the details.
> Maybe #1 and #2 descriptions can be combined and described together.
>
> > This is #1.
> >
> >> \begin{note}
> >> The behavior of the device in response to these commands is best-effort:
> >> @@ -1519,25 +1531,76 @@ \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}
> >>
> >> +The VIRTIO_NET_CTRL_NOTF_COAL_TX_SET and VIRTIO_NET_CTRL_NOTF_COAL_RX_SET
> >> commands use the
> >> +virtio_net_ctrl_coal structure to set \field{max_usecs} and
> >> \field{max_packets} for all
> >> +transmit/receive virtqueues.
> >> +
> >> +The VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET command uses the
> >> virtio_net_ctrl_coal_vq structure
> >> +to set \field{max_usecs} and \field{max_packets} for the supplied
> >> virtqueue number \field{vqn}.
> >> +
> >> +The VIRTIO_NET_CTRL_NOTF_COAL_VQ_GET command gets the values of
> >> \field{max_usecs} and
> >> +\field{max_packets} of the specified virtqueue from the device by setting
> >> \field{vqn}
> >> +in the virtio_net_ctrl_coal_vq structure.
> >> +
> > This is #2.
> >
> >> +# 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-dev] RE: [virtio-comment] Re: [virtio-dev] Re: [PATCH v9] virtio-net: support the virtqueue coalescing moderation
> From: virtio-comm...@lists.oasis-open.org open.org> On Behalf Of Heng Qi
> >>> \subsubsection{Legacy Interface: Framing
> >>> Requirements}\label{sec:Device
> >>> Types / Network Device / Legacy Interface: Framing Requirements}
> >>> --
> >> Let's wait for more comments before the next version, I guess some
> >> may not agree with my comments.
>
> Hi, Michael and Parav, what do you think?
I will review today.
[virtio-dev] Re: [PATCH v9] virtio-net: support the virtqueue coalescing moderation
Hi,
> 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
> Reviewed-by: Xuan Zhuo
> ---
> This patch is on top of Alvaro's latest v7 patch:
> https://lists.oasis-open.org/archives/virtio-dev/202302/msg00431.html .
>
> 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 | 95 +---
> 1 file changed, 87 insertions(+), 8 deletions(-)
>
> diff --git a/device-types/net/description.tex
> b/device-types/net/description.tex
> index e71e33b..71f6827 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}
> @@ -1505,8 +1508,17 @@ \subsubsection{Control Virtqueue}\label{sec:Device
> Types / Network Device / Devi
>
> \paragraph{Notifications Coalescing}\label{sec:Device Types / Network Device
> /
