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 advantage 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 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.
