[ovs-dev] [PATCH] Documentation: Fix DPDK qos example.

William Tu u9012063 at gmail.com
Thu Feb 18 15:10:30 UTC 2021


On Thu, Feb 18, 2021 at 6:55 AM Eelco Chaudron <echaudro at redhat.com> wrote:
>
>
>
> On 18 Feb 2021, at 15:40, William Tu wrote:
>
> > On Thu, Feb 18, 2021 at 1:23 AM Eelco Chaudron <echaudro at redhat.com>
> > wrote:
> >>
> >>
> >>
> >> On 17 Feb 2021, at 18:41, William Tu wrote:
> >>
> >>>>
> >>>>>>  Information Rate). High priority traffic is routed to queue 10,
> >>>>>> which marks
> >>>>>>  all traffic as CIR, i.e. Green. All low priority traffic, queue
> >>>>>> 20,
> >>>>>> is
> >>>>>>  marked as EIR, i.e. Yellow::
> >>>>>>
> >>>>>>      $ ovs-vsctl --timeout=5 set port dpdk1 qos=@myqos -- \
> >>>>>>          --id=@myqos create qos type=trtcm-policer \
> >>>>>> -        other-config:cir=52000 other-config:cbs=2048 \
> >>>>>> -        other-config:eir=52000 other-config:ebs=2048  \
> >>>>
> >>>> 52000 is fine as our documentation states cir, eir are in bytes per
> >>>> second, minus the ethernet header.
> >>>> So (64-12) * 1000 = 52000
> >>>
> >>> How come it's not minus 14-byte ethernet header?
> >>
> >> You are right, it should be 14, miscounted the rte_ether_hdr
> >> structure size :(
> >>
> > Thank you!
> > at vswitchd/vswitch.xml, it uses "46", should I change it to "64- 14 =
> > 50"?
> >         calculated by (pps x packet data size).  For example assuming
> > a user
> >         wishes to limit a stream consisting of 64 byte packets to 1
> > million
> >         packets per second the EIR would be set to to to 46000000.
> > This value
> >         can be broken into '1,000,000 x 46'. Where 1,000,000 is the
> > policing
> >         rate for the number of packets per second and 46 represents
> > the size
> >         of the packet data for a 64 byte ip packet.
> > William
>
> Guess they take of the FCS also, so the packets they sent are 14 bytes
> ethernet, + 46 bytes IP + 4 FCS.

I see, thanks!

>
> In my tests I sent 64 byte packets, i.e. 14 bytes ethernet + 50 bytes
> IP.
>
> Maybe we should clarify this in the text some how?
>
Sure, I will do it.
William


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