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From: Thomas Monjalon <thomas@monjalon.net>
To: Jerin Jacob <jerinjacobk@gmail.com>
Cc: Andrew Rybchenko <arybchenko@solarflare.com>,
	Ferruh Yigit <ferruh.yigit@intel.com>,
	Pavan Nikhilesh <pbhagavatula@marvell.com>,
	Neil Horman <nhorman@tuxdriver.com>,
	John McNamara <john.mcnamara@intel.com>,
	Marko Kovacevic <marko.kovacevic@intel.com>,
	dpdk-dev <dev@dpdk.org>, Ori Kam <orika@mellanox.com>,
	David Marchand <david.marchand@redhat.com>,
	Olivier Matz <olivier.matz@6wind.com>,
	"Ananyev, Konstantin" <konstantin.ananyev@intel.com>
Subject: Re: [dpdk-dev] [PATCH v2 3/3] ethdev: improve flow mark Rx offload deprecation notice
Date: Sat, 23 Nov 2019 19:12:08 +0100
Message-ID: <13121897.9FIjf2LrnR@xps> (raw)
In-Reply-To: <CALBAE1OWf=0S6uiU-V_h+xmHd5vCdF9KCpPhGVr9QuxLjn15Uw@mail.gmail.com>

23/11/2019 10:42, Jerin Jacob:
> On Sat, Nov 23, 2019 at 3:58 AM Thomas Monjalon <thomas@monjalon.net> wrote:
> > 22/11/2019 12:53, Andrew Rybchenko:
> > > On 11/22/19 2:15 PM, Thomas Monjalon wrote:
> > > > 22/11/2019 11:12, Andrew Rybchenko:
> > > >> On 11/22/19 1:01 AM, Thomas Monjalon wrote:
> > > >>> 19/11/2019 13:12, Andrew Rybchenko:
> > > >>>> The deprecation notice is required since it adds more requirements
> > > >>>> when RTE flow mark and flag actions may be used and require
> > > >>>> changes in applications.
> > > >>> I am still not sure what is the best solution here.
> > > >>> I continued to think about it in this thread:
> > > >>>   http://mails.dpdk.org/archives/dev/2019-November/151960.html
> > > >>>
> > > >>> I think we cannot require any application change until 20.11
> > > >>> in order to keep API (and behaviour) compatibility.
> > > >> Expected, but still very disappointing.
> > > >>
> > > >> The feature is implemented by Pavan (@ Marvell), supported by me,
> > > >> used by Qi (@ Intel), looks better than alternatives from application
> > > >> developer point of view [1] and finally postponed for 1 year without really
> > > >> strong motivation.
> > > >
> > > > I see different valuable point of views. This is enough motivation.
> > >
> > > It looks like I miss it in previous discussion, I would be thankful if
> > > you give me links to read or hints how to find.
> >
> > http://mails.dpdk.org/archives/dev/2019-November/150793.html
> >
> > > Introducing new types of controls would make configuration more and
> > > more complex. I think that many different types of control would
> > > over-complicate it. May be it is unavoidable, but it should be clear
> > > why the problem cannot be solved using existing types of controls
> > > (e.g. offloads).
> >
> > The offload control is used as an effective configuration for now.
> > The features which are configured with DEV_RX_OFFLOAD_*
> > do not need any other API to be used.
> > Extending DEV_RX_OFFLOAD_* bits for enabling features which
> > must be configured via other API anyway, is possible.
> > The real problem is that features in DEV_RX_OFFLOAD_* are supposed
> > to be disabled by default. If we add some opt-in features here,
> > we cannot enable them by default for API compatibility and do the
> > right thing by default.
> >
> > Choosing DEV_RX_OFFLOAD_* bits or rte_eth_dev_opt* functions is a detail.
> > The real decision is to change the API for using all these features.
> > Can we keep all features available by default (opt-out)?
> 
> IMO, *rte_eth_dev_opt* has following problems
> 
> 1) It is not multi-process friendly. If we are changing the Rx/Tx
> function pointer, based on
> the selected offload, then, using *rte_eth_dev_opt* scheme won't
> really work(if the new API
> called after the secondary process launch)

Yes it must be used before launching the secondary process.
It is the same as DEV_RX_OFFLOAD_* config.

> 2) If we are taking rte_eth_dev_opt path then by default feature has
> to be enabled to
> not break the functional ABI. That scheme won't scale if as when we
> keep adding the new features.
> It is always easy for the application to define "what it wants" vs
> "what it does not want"

Yes, opt-in may look more natural than opt-out.
But opt-in makes the default more complex, and changes the API.

> 3) Defining the device state after the reconfigure operation.
> 
> IMO, if any operation is connected to fastpath it is better to use
> DEV_RX_OFFLOAD_ like
> this feature where enable or disable PMDs from updating
> ``rte_mbuf::hash::fdir`` so that if possible
> we can use different Rx function pointer if possible(Hence it can work
> with the multi-process case case)

I reply to 2 and 3 together.

We decided that offloads must be disabled by default.
This is what we have in 19.11:
	- Some offloads are enabled before start with DEV_?X_OFFLOAD_*
	- Some offloads are enabled with functions at any time

For the second type of offloads, you want to know, before start,
whether it will be used or not.
If adding the second type of offloads (like rte_flow ones)
to DEV_?X_OFFLOAD_*, it means it must be enabled 2 times:
	- before start with offload bits
	- later with more precise functions

I would like to avoid changing the default behaviour,
which is to enable an offload only one time.
That's why I think this second category of offloads should
offer opt-out (global disabling), so it will continue
to work by default if they are configured.

I hope you understand the difference between the two categories.
For now, it looks I failed to explain it clearly enough.



  reply index

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-19 12:05 [dpdk-dev] [PATCH 1/3] ethdev: remove deprecation notice for packet type set Andrew Rybchenko
2019-11-19 12:05 ` [dpdk-dev] [PATCH 2/3] ethdev: remove deprecation notice about RSS hash offload Andrew Rybchenko
2019-11-19 12:05 ` [dpdk-dev] [PATCH 3/3] ethdev: improve flow mark Rx offload deprecation notice Andrew Rybchenko
2019-11-19 12:12 ` [dpdk-dev] [PATCH v2 1/3] ethdev: remove deprecation notice for packet type set Andrew Rybchenko
2019-11-19 12:12   ` [dpdk-dev] [PATCH v2 2/3] ethdev: remove deprecation notice about RSS hash offload Andrew Rybchenko
2019-11-19 15:04     ` Ferruh Yigit
2019-11-25 16:38       ` Ferruh Yigit
2019-11-19 12:12   ` [dpdk-dev] [PATCH v2 3/3] ethdev: improve flow mark Rx offload deprecation notice Andrew Rybchenko
2019-11-21 22:01     ` Thomas Monjalon
2019-11-22 10:12       ` Andrew Rybchenko
2019-11-22 11:15         ` Thomas Monjalon
2019-11-22 11:53           ` Andrew Rybchenko
2019-11-22 13:32             ` Jerin Jacob
2019-11-22 18:58             ` Thomas Monjalon
2019-11-23  9:42               ` Jerin Jacob
2019-11-23 18:12                 ` Thomas Monjalon [this message]
2019-11-25 10:44                   ` Jerin Jacob
2019-11-25 11:39                     ` Thomas Monjalon
2019-12-02  4:21                       ` Jerin Jacob
2019-12-02  9:15                         ` Thomas Monjalon
2019-12-02 11:09                           ` Jerin Jacob
2019-12-02 11:57                             ` Andrew Rybchenko
2019-12-05  8:12                               ` Jerin Jacob
2019-12-09  9:17                                 ` Andrew Rybchenko
2019-12-16  7:38                                   ` Jerin Jacob
2019-12-16 10:02                                     ` Andrew Rybchenko
2019-11-19 15:04   ` [dpdk-dev] [PATCH v2 1/3] ethdev: remove deprecation notice for packet type set Ferruh Yigit
2019-11-25 16:38     ` Ferruh Yigit

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