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Subject: Re: [PATCH v9] virtio-net: support device stats
On Mon, 28 Feb 2022 17:07:54 +0800, Jason Wang <jasowang@redhat.com> wrote:
> On Tue, Feb 15, 2022 at 3:47 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
> >
> > This patch allows the driver to obtain some statistics from the device.
> >
> > In the back-end implementation, we can count a lot of such information,
> > which can be used for debugging and judging the running status of the
> > back-end. We hope to directly display it to the user through ethtool.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > ---
> > conformance.tex | 2 +
> > content.tex | 135 ++++++++++++++++++++++++++++++++++++++++++++++--
> > 2 files changed, 134 insertions(+), 3 deletions(-)
> >
> > diff --git a/conformance.tex b/conformance.tex
> > index 42f8537..950924e 100644
> > --- a/conformance.tex
> > +++ b/conformance.tex
> > @@ -142,6 +142,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
> > \item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Automatic receive steering in multiqueue mode}
> > \item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Offloads State Configuration / Setting Offloads State}
> > \item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) }
> > +\item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Device stats}
> > \end{itemize}
> >
> > \conformance{\subsection}{Block Driver Conformance}\label{sec:Conformance / Driver Conformance / Block Driver Conformance}
> > @@ -401,6 +402,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
> > \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Gratuitous Packet Sending}
> > \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Automatic receive steering in multiqueue mode}
> > \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) / RSS processing}
> > +\item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Device stats}
> > \end{itemize}
> >
> > \conformance{\subsection}{Block Device Conformance}\label{sec:Conformance / Device Conformance / Block Device Conformance}
> > diff --git a/content.tex b/content.tex
> > index c6f116c..818275d 100644
> > --- a/content.tex
> > +++ b/content.tex
> > @@ -3092,6 +3092,9 @@ \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_CTRL_STATS(55)] Device can provide device-level statistics
> > + to the driver through the control channel.
> > +
> > \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.
> > @@ -3137,6 +3140,7 @@ \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_CTRL_STATS] 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}
> > @@ -4015,6 +4019,7 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
> > u8 command;
> > u8 command-specific-data[];
> > u8 ack;
> > + u8 command-specific-data-reply[];
> > };
> >
> > /* ack values */
> > @@ -4023,9 +4028,13 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
> > \end{lstlisting}
> >
> > The \field{class}, \field{command} and command-specific-data are set by the
> > -driver, and the device sets the \field{ack} byte. There is little it can
> > -do except issue a diagnostic if \field{ack} is not
> > -VIRTIO_NET_OK.
> > +driver, and the device sets the \field{ack} byte and optionally
> > +\field{command-specific-data-reply}. There is little the driver can
> > +do except issue a diagnostic if \field{ack} is not VIRTIO_NET_OK.
> > +
> > +These commands VIRTIO_NET_CTRL_STATS_GET_DEV,
> > +VIRTIO_NET_CTRL_STATS_GET_CTRL_VQ, and VIRTIO_NET_CTRL_STATS_GET_QUEUE_PAIR contain
> > +\field{command-specific-data-reply}.
> >
> > \paragraph{Packet Receive Filtering}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Packet Receive Filtering}
> > \label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Setting Promiscuous Mode}%old label for latexdiff
> > @@ -4471,6 +4480,126 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
> > according to the native endian of the guest rather than
> > (necessarily when not using the legacy interface) little-endian.
> >
> > +\paragraph{Device stats}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Device stats}
> > +
> > +If the VIRTIO_NET_F_CTRL_STATS feature is negotiated, the driver can
> > +get device stats from the device in \field{command-specific-data-reply}.
> > +
> > +To get the stats, the following definitions are used:
> > +\begin{lstlisting}
> > +#define VIRTIO_NET_CTRL_STATS 6
> > +#define VIRTIO_NET_CTRL_STATS_GET_DEV 0
> > +#define VIRTIO_NET_CTRL_STATS_GET_CTRL_VQ 1
> > +#define VIRTIO_NET_CTRL_STATS_GET_QUEUE_PAIR 2
> > +\end{lstlisting}
> > +
> > +The following layout structures are used:
> > +
> > +\field{command-specific-data}
> > +\begin{lstlisting}
> > +struct virtio_net_ctrl_stats_queue_pair {
> > + le64 queue_pair_index;
> > +}
> > +\end{lstlisting}
> > +
> > +\field{command-specific-data-reply}
> > +\begin{lstlisting}
> > +struct virtio_net_ctrl_reply_stats_dev {
> > + le64 mac_unicast_num; /* The number of unicast mac addresses. */
> > + le64 mac_multicast_num; /* The number of multicast mac addresses. */
> > + le64 vlan_num; /* The number of vlan. */
> > +}
>
> This looks more like the states instead of the stats? And the driver
> should have the knowledge of those. Or is there any chance that the
> device knowledge can differ from the driver's?
I'm really not sure if we want these stats, or if we just leave dev stats empty.
>
> > +
> > +struct virtio_net_ctrl_reply_stats_cvq {
> > + le64 command_num; /* The number of commands, including the current command. */
> > + le64 ok_num; /* The number of commands (including the current command) where the ack was VIRTIO_NET_OK. */
> > +}
> > +
> > +struct virtio_net_ctrl_reply_stats_queue_pair {
> > + /* rx stats */
> > + le64 rx_packets; /* The number of packets received by device (not the packets passed to the guest), including the dropped packets by device. */
> > + le64 rx_bytes; /* The number of bytes received by device (not the packets passed to the guest), including the dropped packets by device. */
> > +
> > + le64 rx_notification; /* The number of notifications from driver. */
> > + le64 rx_interrupt; /* The number of interrupts generated by device. */
> > +
> > + le64 rx_drop; /* The number of packets dropped by the rx queue. Contains all kinds of packet drop. */
> > + le64 rx_drop_overruns; /* The number of packets dropped by the rx queue when no more descriptors were available. */
> > +
> > + le64 rx_csum_valid; /* The number of packets with VIRTIO_NET_HDR_F_DATA_VALID. */
> > + le64 rx_csum_partial; /* The number of packets with VIRTIO_NET_HDR_F_NEEDS_CSUM. */
> > + le64 rx_csum_bad; /* The number of packets with abnormal csum. */
> > + le64 rx_csum_none; /* The number of packets without hardware csum. */
> > +
> > + le64 rx_gso_packets; /* The number of GSO packets written into the RX VQ buffers. */
> > + le64 rx_gso_bytes; /* The number of bytes(excluding the virtio net header) of the GSO packets written into the RX VQ buffers. */
> > + le64 rx_reset; /* The number of queue resets. */
> > +
> > + /* tx stats */
> > + le64 tx_packets; /* The number of packets sent by device (not the packets received from the guest), excluding the dropped packets by device. */
> > + le64 tx_bytes; /* The number of bytes sent by device (not the packets received from the guest), excluding the dropped packets by device. */
> > +
> > + le64 tx_notification; /* The number of notifications from driver. */
> > + le64 tx_interrupt; /* The number of interrupts generated by device. */
> > +
> > + le64 tx_drop; /* The number of packets dropped by the tx queue. Contains all kinds of packet drop. */
> > + le64 tx_drop_malformed; /* The number of packets dropped when the descriptor is in an error state. */
> > +
> > + le64 tx_csum_none; /* The number of packets that doesn't require hardware csum. */
> > + le64 tx_csum_partial; /* The number of packets that requires hardware csum. */
>
> s/requires/require/
>
> > +
> > + le64 tx_gso_packets; /* The number of GSO packets that the device received from the driver. */
> > + le64 tx_gso_bytes; /* The number of bytes(excluding the virtio net header) of GSO packets that the device received from the driver. */
> > + le64 tx_reset; /* The number of queue resets. */
> > +}
> > +\end{lstlisting}
>
> I wonder if it's better to use description/item to explain the fields
> one by one instead of using comments.
>
> E.g for some fields, we need to explain that the value is valid only
> if some specific feature is negotiated (e.g gso or reset)?
>
> Rethink of the structure, I also wonder if it's better to restructure
> the stats to
>
> struct stats{
> /* the counters that doesn't need any features */
> /* the counters that needs CSUM */
> /* the counters that needs GSO */
> /* the counters that needs reset */
> }
>
> Or even split them into different commands. The reason is that the
> current design requires the knowledge of a feature even if it doesn't
> support it.
I think this is a good idea.
>
> > +
> > +See \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Virtqueue Reset}
> > +for more about \field{rx_reset} and \field{tx_reset}.
> > +
> > +All device stats are divided into three categories:
> > +\begin{itemize}
> > + \item the stats of the device.
> > + \begin{description}
> > + \item[command] VIRTIO_NET_CTRL_STATS_GET_DEV
> > + \item[command-specific-data-reply] virtio_net_ctrl_reply_stats_dev
> > + \end{description}
> > +
> > + \item the stats of the controlq.
> > + \begin{description}
> > + \item[command] VIRTIO_NET_CTRL_STATS_GET_CTRL_VQ
> > + \item[command-specific-data-reply] virtio_net_ctrl_reply_stats_cvq
> > + \end{description}
> > +
> > + \item the stats of the queue pair. This contains the stats of rx and tx.
> > + \begin{description}
> > + \item[command] VIRTIO_NET_CTRL_STATS_GET_QUEUE_PAIR
> > + \item[command-specific-data] virtio_net_ctrl_stats_queue_pair
> > + \item[command-specific-data-reply] virtio_net_ctrl_reply_stats_queue_pair
> > + \end{description}
> > +\end{itemize}
> > +
> > +
> > +\devicenormative{\subparagraph}{Device stats}{Device Types / Network Device / Device Operation / Control Virtqueue / Device stats}
> > +
> > +If VIRTIO_NET_F_CTRL_STATS has been negotiated, the device MUST support the
> > +VIRTIO_NET_CTRL_STATS_GET_DEV, VIRTIO_NET_CTRL_STATS_GET_CTRL_VQ and
> > +VIRTIO_NET_CTRL_STATS_GET_QUEUE_PAIR commands.
> > +
> > +If \field{queue_pair_index} is out of range for a
> > +VIRTIO_NET_CTRL_STATS_GET_QUEUE_PAIR command, the device MUST set \field{ack} in
> > +virtio_net_ctrl to VIRTIO_NET_ERR.
> > +
> > +If VIRTIO_NET_F_GUEST_CSUM is not successfully negotiated, all csum related
> > +metrics MUST be 0.
>
> It's better to move this to the guidance part.
>
> > +
> > +GSO packet refers to the packet of gso_type != VIRTIO_NET_HDR_GSO_NONE.
>
> We'd better use English instead of "!=" here.
>
> > +All statistics on GSO MUST be based on the GSO packets.
>
> As discussed above, we need to also add the part of reset.
OK.
Thanks.
>
> Thanks
>
> > +
> > +\drivernormative{\subparagraph}{Device stats}{Device Types / Network Device / Device Operation / Control Virtqueue / Device stats}
> > +
> > +\field{command-specific-data} MUST be empty for VIRTIO_NET_CTRL_STATS_GET_DEV
> > +and VIRTIO_NET_CTRL_STATS_GET_CTRL_VQ.
> >
> > \subsubsection{Legacy Interface: Framing Requirements}\label{sec:Device
> > Types / Network Device / Legacy Interface: Framing Requirements}
> > --
> > 2.31.0
> >
>
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