On Wed, Feb 1, 2023 at 2:37 PM Andrew Rybchenko
<andrew.rybche...@oktetlabs.ru> wrote:
>
> On 2/1/23 12:05, Thomas Monjalon wrote:
> > 01/02/2023 10:00, Ori Kam:
> >> Hi all,
> >>
> >> Sorry for jumping in late,
> >>
> >>> -----Original Message-----
> >>> From: Jerin Jacob <jerinjac...@gmail.com>
> >>> Sent: Wednesday, 1 February 2023 10:53
> >>>
> >>> On Wed, Feb 1, 2023 at 12:46 PM Andrew Rybchenko
> >>> <andrew.rybche...@oktetlabs.ru> wrote:
> >>>>
> >>>> On 2/1/23 09:10, Ivan Malov wrote:
> >>>>> Hello everyone,
> >>>>>
> >>>>> Since making automatic, or implicit, offload decisions does
> >>>>> not belong in testpmd responsibility domain, it should be
> >>>>> safer to avoid calling the "negotiate metadata delivery"
> >>>>> API with some default selection unless the user asks to
> >>>>> do so explicitly, via internal CLI or app options.
> >>>>>
> >>>>> With that in mind, port config <port_id> ... sounds OK.
> >>>>>
> >>>>> PMDs that support flow primitives which can generate metadata
> >>>>> but, if in started state, can't enable its delivery may pass
> >>>>> appropriate rte_error messages to the user suggesting
> >>>>> they enable delivery of such metadata from NIC to PMD
> >>>>> first. This way, if the person operating testpmd
> >>>>> enters a flow create command and that fails,
> >>>>> they can figure out the inconsistency, stop
> >>>>> the port, negotiate, start and try again.
> >>>>>
> >>>>> As for non-debug applications, their developers shall
> >>>>> be properly informed about the problem of enabling
> >>>>> delivery of metadata from NIC to PMD. This way,
> >>>>> they will invoke the negotiate API by default
> >>>>> in their apps, with the feature selection (eg.
> >>>>> MARK) as per nature of the app's business.
> >>>>>
> >>>>> This API should indeed be helpful to some PMDs with
> >>>>> regard to collecting upfront knowledge like this.
> >>>>> At the same time, should be benign to those PMDs
> >>>>> who do not need this knowledge and can enable
> >>>>> delivery of metadata right when inserting the
> >>>>> flow rules. So I hope the API does not create
> >>>>> too much discomfort to vendors not needing it.
> >>>>>
> >>>>> Thank you.
> >>>>>
> >>>>> On Wed, 1 Feb 2023, Thomas Monjalon wrote:
> >>>>>
> >>>>>> 31/01/2023 17:17, Jerin Jacob:
> >>>>>>> On Fri, Jan 27, 2023 at 8:31 PM Thomas Monjalon
> >>> <tho...@monjalon.net>
> >>>>>>> wrote:
> >>>>>>>>
> >>>>>>>> 27/01/2023 11:42, Nithin Kumar Dabilpuram:
> >>>>>>>>> From: Thomas Monjalon <tho...@monjalon.net>
> >>>>>>>>>> 27/01/2023 06:02, Nithin Kumar Dabilpuram:
> >>>>>>>>>>> From: Thomas Monjalon <tho...@monjalon.net>
> >>>>>>>>>>>> Ferruh is proposing to have a command "port config <port_id>
> >>> ..."
> >>>>>>>>>>>> to configure the flags to negotiate.
> >>>>>>>>>>>> Are you OK with this approach?
> >>>>>>>>>>>
> >>>>>>>>>>> Yes, we are fine to have such command to enable and disable the
> >>>>>>>>>>> feature
> >>>>>>>>>>> with default being it disabled if supported by PMD.
> >>>>>>>>>>> Is default being disabled fine if the feature is supported by a
> >>>>>>>>>>> PMD ?
> >>>>>>>>>>
> >>>>>>>>>> I think the default should be enabled for ease of use.
> >>>>>>>>>
> >>>>>>>>> Since testpmd is used extensively for benchmarking purposes, we
> >>>>>>>>> thought it should have minimum features
> >>>>>>>>> enabled by default. The default testpmd doesn't have any Rx/Tx
> >>>>>>>>> offloads enabled(except for FAST FREE), default
> >>>>>>>>> fwd mode being "iofwd" and the Rx metadata is only referenced
> >>> when
> >>>>>>>>> dumping packets.
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>> Do we have similar features disables by default?
> >>>>>>>>>> I mean do we know features in testpmd which require a "double
> >>>>>>>>>> enablement"
> >>>>>>>>>> like one configuration command + one rte_flow rule?
> >>>>>>>>>
> >>>>>>>>> Spec itself is that way i.e "RTE_FLOW_RULE +
> >>>>>>>>> RX_METADATA_NEGOTIATE(once)"
> >>>>>>>>>
> >>>>>>>>> Isn't it enough if
> >>>>>>>>>
> >>>>>>>>> #1 We have enough print when rte_flow is being create without
> >>>>>>>>> negotiation done and ask user to enable rx metadata using
> >>>>>>>>> "port config <port_id>..."
> >>>>>>>>> #2 Provide testpmd app arg to enable Rx metadata(for example "
> >>>>>>>>> --rx-metadata") like other features to avoid calling another
> >>>>>>>>> command before rte flow create.
> >>>>>>>>
> >>>>>>>> I'm not sure what is best.
> >>>>>>>> I will let others discuss this part.
> >>>>>>>
> >>>>>>> IMO, enabling something always defeat the purpose to negotiate. IMO,
> >>>>>>> someone needs to negotiate
> >>>>>>> for a feature if the feature is needed. I think, the double enablement
> >>>>>>> is part of the spec itself. In case, The PMD
> >>>>>>> drivers won't like double enablement, no need to implement the PMD
> >>>>>>> callback. That way, there is no change in the existing flow.
> >>>>>>>
> >>>>>>> The reason why cnxk driver thought of leveraging negotiate() feature
> >>>>>>> so that it helps for optimization. e.s.p
> >>>>>>> function template for multiprocess case as we know what features
> >>>>>>> needed in fastpath upfront.
> >>>>>>>
> >>>>>>> If there still concerns with patch we can take up this to TB decide
> >>>>>>> one way or another to make forward progress. Let us know.
> >>>>>>
> >>>>>> Ferruh, Andrew, Ori, Ivan, what is your opinion?
> >>>>>> Let's progress with this patch to make it in -rc1.
> >>>>
> >>>> As I understand all agreed that we need testpmd command to
> >>>> control negotiated Rx metadata. May be even command-line
> >>>> option would be useful.
> >>>>
> >>>> So, remaining question is what should be the default value in
> >>>> testpmd. Note that it is just testpmd question since default
> >>>> value in an abstract application is nothing negotiated
> >>>> (if I'm not mistaken).
> >>>>
> >>>> The key advantaan ge of the current behaviour is to avoid
> >>>> "double-enabling" in testpmd. It preserves behaviour which
> >>>> we had before before the API addition. It is a strong
> >>>> argument. Basically it puts the feature into the same
> >>>> basket as FAST_FREE - need an action to run faster.
> >>>
> >>> I think, there is a disconnect here. FAST_FREE is enabled by default.
>
> Sorry, I'm lost here. Don't we need to enable FAST_FREE
> offload? As far as I know all offloads are disabled by default.
Not the case for FAST_FREE as disabling needs "more cycles on processor" side.
See app/test-pmd/testpmd.c
/*
* Ethernet device configuration.
*/
struct rte_eth_rxmode rx_mode;
struct rte_eth_txmode tx_mode = {
.offloads = RTE_ETH_TX_OFFLOAD_MBUF_FAST_FREE,
};
>
> >>> i.e We don't need any specific action to run faster. To align with
> >>> performance
> >>> test application, by default the configuration should be run faster. User
> >>> needs to give explicit configuration to allow more offload or the one
> >>> causes
> >>> the mpps drops. IMO, That is the theme followed in testpmd.
> >>>
> >>>
> >> I agree with Andrew, the default should stay the same, as now, PMD may
> >> already implement
> >> logic to only enable the feature if there is a flow rule.
> >> Changing the default will result in breaking applications.
> >
> > That's not what is discussed here.
> > We are talking only about testpmd default.
> >
> >> I want to suggest new approach for this feature,
> >> maybe we can use the rte_flow_configure, and add a new bit that says if
> >> those
> >> actions are going to be used.
> >> What do you think?
> >
> > Let's not change the API please.
> >
> >
> >>>> I see no problem in such approach.
> >>>>
> >>>> The key disadvantage is the difference in testpmd and
> >>>> other applications default behaviour.
> >>>>
> >>>> I'd look at the feature in the following way:
> >>>> if an application theoretically wants to use
> >>>> USER_FLAG, USER_MARK or TUNNEL_ID it must negotiate
> >>>> corresponding Rx metadata to ensure that the feature is
> >>>> available and HW is informed that application may need it.
> >>>> Since testpmd supports corresponding flow API actions and
> >>>> flow tunnels, it tries to negotiate it by default, but do
> >>>> not fail if the negotiation fails.
> >>>>
> >>>> So, I'd would vote to keeping the default value as is.
> >>>>
> >>
> >
> >
> >
> >
> >
>
