Re: [virtio-dev] [PATCH] virtio-net: support timestamp received packet

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

On Wed, 19 Oct 2022 14:40:46 +0800, Shuyi Cheng <chengshuyi@linux.alibaba.com> wrote:
>
>
> å 10/19/22 9:56 AM, Xuan Zhuo åé:
> > On Wed, 19 Oct 2022 09:32:39 +0800, Shuyi Cheng <chengshuyi@linux.alibaba.com> wrote:
> >> This patch introduces VIRTIO_NET_F_RX_TSTAMP to enhance the
> >> observability of network packet delay between virtio device and virtio
> >> driver.
> >>
> >> We have encountered many network jitter problems from virtio device to
> >> virtio driver in the production environment. Due to the lack of relevant
> >> indicators in this path, we often spend a lot of energy to locate such
> >> problems. If the virtio device can provide the packet receiving
> >> timestamp, then we can easily calculate the network jitter index between
> >> the virtio device and the virtio driver. When such a problem is
> >> encountered again, it is easy to determine the problem boundary.
> >>
> >> Thanks and looking forward to your response!
> >
> >
> > 1. Do we need to dynamically turn on and off this function?
> > 2. What is the unit of tstamp here?
> >
> > Thanks.
> >
>
> 1. yes, we could use ethtool to dynamically turn on and off this function.

But at present, you don't support dynamic modification, do you?

>
> 2. nanosecond precision is ok.

Please specify this in the spec.

Thanks.

>
> Thanks.
>
> >
> >>
> >> Signed-off-by: Shuyi Cheng <chengshuyi@linux.alibaba.com>
> >> ---
> >>    content.tex | 14 ++++++++++++++
> >>    1 file changed, 14 insertions(+)
> >>
> >> diff --git a/content.tex b/content.tex
> >> index e863709..472acf3 100644
> >> --- a/content.tex
> >> +++ b/content.tex
> >> @@ -3097,6 +3097,8 @@ \subsection{Feature bits}\label{sec:Device Types /
> >> Network Device / Feature bits
> >>    \item[VIRTIO_NET_F_HASH_REPORT(57)] Device can report per-packet hash
> >>        value and a type of calculated hash.
> >>
> >> +\item[VIRTIO_NET_F_RX_TSTAMP(58)] Device can timestamp received packet.
> >> +
> >>    \item[VIRTIO_NET_F_GUEST_HDRLEN(59)] Driver can provide the exact
> >> \field{hdr_len}
> >>        value. Device benefits from knowing the exact header length.
> >>
> >> @@ -3371,6 +3373,7 @@ \subsection{Device Operation}\label{sec:Device
> >> Types / Network Device / Device O
> >>    #define VIRTIO_NET_HDR_F_NEEDS_CSUM    1
> >>    #define VIRTIO_NET_HDR_F_DATA_VALID    2
> >>    #define VIRTIO_NET_HDR_F_RSC_INFO      4
> >> +#define VIRTIO_NET_HDR_F_TSTAMP        8
> >>            u8 flags;
> >>    #define VIRTIO_NET_HDR_GSO_NONE        0
> >>    #define VIRTIO_NET_HDR_GSO_TCPV4       1
> >> @@ -3387,6 +3390,7 @@ \subsection{Device Operation}\label{sec:Device
> >> Types / Network Device / Device O
> >>            le32 hash_value;        (Only if VIRTIO_NET_F_HASH_REPORT
> >> negotiated)
> >>            le16 hash_report;       (Only if VIRTIO_NET_F_HASH_REPORT
> >> negotiated)
> >>            le16 padding_reserved;  (Only if VIRTIO_NET_F_HASH_REPORT
> >> negotiated)
> >> +        le64 tstamp;            (Only if VIRITO_NET_F_RX_TSTAMP negotiated)
> >>    };
> >>    \end{lstlisting}
> >>
> >> @@ -3809,6 +3813,13 @@ \subsubsection{Processing of Incoming
> >> Packets}\label{sec:Device Types / Network
> >>    checksum (in case of multiple encapsulated protocols, one level
> >>    of checksums is validated).
> >>
> >> +If VIRTIO_NET_F_RX_TSTAMP was not negotiated, the device MUST not set
> >> +VIRTIO_NET_HDR_F_TSTAMP bit in \field{flags}.
> >> +
> >> +If VIRTIO_NET_F_RX_TSTAMP was negotiated, the device MUST also
> >> +set VIRTIO_NET_HDR_F_TSTAMP bit in \field{flags},
> >> +set \field{tstamp} to time to receive the packet.
> >> +
> >>    \drivernormative{\paragraph}{Processing of Incoming
> >>    Packets}{Device Types / Network Device / Device Operation /
> >>    Processing of Incoming Packets}
> >> @@ -3831,6 +3842,9 @@ \subsubsection{Processing of Incoming
> >> Packets}\label{sec:Device Types / Network
> >>    VIRTIO_NET_HDR_F_DATA_VALID is set, the driver MUST NOT
> >>    rely on the packet checksum being correct.
> >>
> >> +If VIRTIO_NET_HDR_F_TSTAMP bit in \field{flags} is not set, the
> >> +driver MUST NOT use the \field{tstamp}.
> >> +
> >>    \paragraph{Hash calculation for incoming packets}
> >>    \label{sec:Device Types / Network Device / Device Operation /
> >> Processing of Incoming Packets / Hash calculation for incoming packets}
> >>
> >> --
> >> 2.27.0
> >>
> >>
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