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

[Shuyi Cheng <chengshuyi@linux.alibaba.com>]

å 10/19/22 2:41 PM, Xuan Zhuo åé:
> 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?

Yes, i will add it.

Thanks.

> > 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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