Re: [dpdk-dev] [PATCH 1/8] ethdev: introduce sample action for rte flow

[Jerin Jacob <jerinjacobk@gmail.com>]

On Fri, Jun 26, 2020 at 4:16 PM Thomas Monjalon <thomas@monjalon.net> wrote:
>
> 26/06/2020 12:35, Jerin Jacob:
> > On Fri, Jun 26, 2020 at 12:59 AM Thomas Monjalon <thomas@monjalon.net> wrote:
> > >
> > > 25/06/2020 19:55, Jerin Jacob:
> > > > On Thu, Jun 25, 2020 at 10:20 PM Jiawei Wang <jiaweiw@mellanox.com> wrote:
> > > > >
> > > > > When using full offload, all traffic will be handled by the HW, and
> > > > > directed to the requested vf or wire, the control application loses
> > > > > visibility on the traffic.
> > > > > So there's a need for an action that will enable the control application
> > > > > some visibility.
> > > > >
> > > > > The solution is introduced a new action that will sample the incoming
> > > > > traffic and send a duplicated traffic in some predefined ratio to the
> > > > > application, while the original packet will continue to the target
> > > > > destination.
> > > > >
> > > > > The packets sampled equals is '1/ratio', if the ratio value be set to 1
> > > > > , means that the packets would be completely mirrored. The sample packet
> > > > > can be assigned with different set of actions from the original packet.
> > > > >
> > > > > In order to support the sample packet in rte_flow, new rte_flow action
> > > > > definition RTE_FLOW_ACTION_TYPE_SAMPLE and structure rte_flow_action_sample
> > > >
> > > > Isn't mirroring the packet? How about, RTE_FLOW_ACTION_TYPE_MIRROR
> > > > I am not able to understand, Why it is called sample.
> > >
> > > Sampling is a partial mirroring.
> >
> > I think, By definition, _sampling_ is the _selection_ of items from a
> > specific group.
> > I think, _sampling_ is not dictating, what is the real action for the
> > "selected"  items.
> > One can get confused with the selected ones can be for forward, drop
> > any other action.
>
> I see. Good design question (I will let others reply).
>
> > So IMO, explicit mirror keyword usage makes it is clear.
> >
> > Some more related questions:
> > 1) What is the real use case for ratio? I am not against adding a
> > ratio attribute if the MLX hardware supports it. It will be good to
> > know the use case from the application perspective? And what basics
> > application set ratio != 1?
>
> If I understand well, some applications want to check,
> by picking random packets, that the processing is not failing.

Not clear to me. I will wait for another explanation if any.
In what basics application set .1 vs .8?

>
> > 2) If it is for "rate-limiting" or "policing", why not use rte_mtr
> > object (rte_mtr.h) via rte_flow action.
> > 3) One of the issue for driver developers and application writers are
> > overlapping APIs. This would overlap with rte_eth_mirror_rule_set()
> > API.
> >
> > Can we deprecate rte_eth_mirror_rule_set() API? It will be a pain for
> > all to have overlapping APIs. We have not fixed the VLAN filter API
> > overlap with rte_flow in ethdev. Its being TODO for multiple releases
> > now.
>
> Ooooooooh yes!
> I think flow-based API is more powerful, and should deprecate
> old port-based API.

+1 from me.

it is taking too much effort and time to make support duplicate APIs.

> I want to help deprecating such API in 20.11 if possible.

Please start that discussion. In this case, it is clear API overlap
with rte_eth_mirror_rule_set().
We should not have two separate paths for the same function in the
same ethdev library.



>
> > > Full mirroring is sampling 100% packets (ratio = 1).
> > > That's why only one action is enough.
>
>
>