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Subject: Re: [PATCH v9] virtio-net: support device stats
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?
> +
> +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.
> +
> +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.
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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