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 > > And no, it is not postponed by one year. > > Next release can implement a new API. > > > >> I disagree that it is tightly related to moving > >> mark/flag to > >> dynamic field/flag and absolutely blocked by it. Yes, I know that the are > >> concerns from the very beginning, but the problem is explained [2] and > >> clear > >> and no full-featured alternative solution is suggested. Solution suggested > >> by Ori has many significant drawbacks as explained in [2] and highlighted > >> in further discussion. > > > > I disagree with working only on mark action while there are a lot > > of other configs which have to be implemented in drivers. > > > > The reality is that some drivers decided to have some "optimizations" > > disabling some features, and you want the application to opt-in > > in order to allow your optimized paths. > > Strictly speaking it is not about driver optimized paths only, but HW > configuration as well which can be done on start-up only (not dynamic) and > could be per-queue in fact. OK good point, we can optimize both driver and hardware configuration before enabling a queue. Note all these threads are long but one of the benefits is to get the definition of the need, which was lacking. > > Note that opt-in is different of really enabling an offload. > > For some basic port-level features like RSS hash, > > it is enabled with an offload flag before starting the port, > > acting as an opt-in. > > Could you highlight the difference between opt-in and offload. > What is the key difference which makes one solution better > than another? Why different mechanism is required? Configuring a feature means providing all infos to make the processing effective. Opt-in a feature means asking for a processing to be available when it will be configured later. Configuration implies opt-in of course. For now, we have only configuration APIs, no opt-in. The need you want to address is to opt-in for a feature before enabling a queue, and configure it later. > > Some features have some dedicated API, which may be enabled after > > starting the port, and no way to opt-in (or opt-out) before start. > > It sounds like you have examples in your mind. Please, share. All rte_flow examples are some examples of configuration API which can be done after start, without a way to opt-in in advance. Other examples of APIs not clearly forbidden to use after start: - rte_eth_dev_set_mtu() - rte_eth_dev_vlan_filter() - rte_eth_dev_rss_reta_update() - rte_eth_mirror_rule_set() - rte_eth_dev_udp_tunnel_port_add() - rte_eth_dev_l2_tunnel_offload_set - rte_eth_timesync_enable() > > A lot of features are using rte_flow API which is in this situation. > > If we take the opt-in path, let's not do it only for the mark action, > > but let's create a real API for it: > > rte_eth_dev_optin() > > rte_eth_dev_optinall() > > rte_eth_dev_optoutl() > > 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)? And more importantly, again, it should be done for all features at once, not only for the rte_flow mark. > > I think the motivation is strong enough. > > > >> [1] http://inbox.dpdk.org/dev/1573203631946.15...@kth.se/ > >> [2] > >> http://inbox.dpdk.org/dev/f170105b-9c60-1b04-cb18-52e0951dd...@solarflare.com/ > >> > >>> If something would be implemented in 20.02, > >>> it must be a new and optional API. > >> > >> Flow mark and flag may work without the offload with some drivers, > >> but some drivers require the offload to make it work. Flow API error > >> should contain message which says that the offload is disabled and > >> must be enabled. > > > > Yes, the PMD should return an explicit error about a feature being disabled. > > How does it impact ethdev API? > > It is still the offload discussed in the deprecation notice. > The solution is far from ideal, since allows the difference in PMDs > behaviour and an application debugged on one PMD may not > work using another PMD (unfortunately it is true in any case, but > such definition makes it 100% legal). Do you mean PMDs have different capabilities and optimizations? I think I don't get your point. > >>> That's why I think no deprecation notice is required. > >>> > >>> [...] > >>>> +* ethdev: New offload flag ``DEV_RX_OFFLOAD_FLOW_MARK`` will be added > >>>> in 20.02. > >>>> + This will provide application an information if > >>>> ``RTE_FLOW_ACTION_TYPE_MARK`` > >>>> + or ``RTE_FLOW_ACTION_TYPE_FLAG`` is supported and, what is more > >>>> important, > >>>> + allow an application to let PMD know that it would like to use these > >>>> + features. > >>>> + PMD may use the information to choose optimal datapath implementation > >>>> and > >>>> + configure HW appropriately to optimize performance and/or resources > >>>> usage.
