Hi Thomas, Ferruh, Andrew,
> -----Original Message----- > From: Thomas Monjalon [mailto:tho...@monjalon.net] > Sent: Monday, October 22, 2018 8:13 PM > To: dev@dpdk.org > Cc: Yigit, Ferruh <ferruh.yi...@intel.com>; Andrew Rybchenko > <arybche...@solarflare.com>; Lu, Wenzhuo <wenzhuo...@intel.com> > Subject: Re: [dpdk-dev] [PATCH v2] ethdev: fix device info getting > > 22/10/2018 14:01, Ferruh Yigit: > > On 8/23/2018 9:58 AM, Andrew Rybchenko wrote: > > > On 22.08.2018 19:55, Ferruh Yigit wrote: > > >> On 8/14/2018 1:57 AM, Lu, Wenzhuo wrote: > > >>> Hi Andrew, > > >>> > > >>>> -----Original Message----- > > >>>> From: Andrew Rybchenko [mailto:arybche...@solarflare.com] > > >>>> Sent: Monday, August 13, 2018 4:39 PM > > >>>> To: Lu, Wenzhuo <wenzhuo...@intel.com>; Thomas Monjalon > > >>>> <tho...@monjalon.net>; Yigit, Ferruh <ferruh.yi...@intel.com> > > >>>> Cc: dev@dpdk.org > > >>>> Subject: Re: [dpdk-dev] [PATCH v2] ethdev: fix device info > > >>>> getting > > >>>> > > >>>> On 13.08.2018 05:50, Lu, Wenzhuo wrote: > > >>>>> Hi Thomas, > > >>>>> > > >>>>> > > >>>>>> -----Original Message----- > > >>>>>> From: Thomas Monjalon [mailto:tho...@monjalon.net] > > >>>>>> Sent: Wednesday, August 1, 2018 11:37 PM > > >>>>>> To: Lu, Wenzhuo <wenzhuo...@intel.com>; Andrew Rybchenko > > >>>>>> <arybche...@solarflare.com>; Yigit, Ferruh > > >>>>>> <ferruh.yi...@intel.com> > > >>>>>> Cc: dev@dpdk.org > > >>>>>> Subject: Re: [dpdk-dev] [PATCH v2] ethdev: fix device info > > >>>>>> getting > > >>>>>> > > >>>>>> 16/07/2018 03:58, Lu, Wenzhuo: > > >>>>>>> Hi Andrew, > > >>>>>>> > > >>>>>>>> -----Original Message----- > > >>>>>>>> From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Lu, > > >>>>>>>> Wenzhuo > > >>>>>>>> Sent: Monday, July 16, 2018 9:08 AM > > >>>>>>>> To: Andrew Rybchenko <arybche...@solarflare.com>; > > >>>>>>>> dev@dpdk.org > > >>>>>>>> Cc: Yigit, Ferruh <ferruh.yi...@intel.com>; Thomas Monjalon > > >>>>>>>> <tho...@monjalon.net> > > >>>>>>>> Subject: Re: [dpdk-dev] [PATCH v2] ethdev: fix device info > > >>>>>>>> getting > > >>>>>>>> > > >>>>>>>> Hi Andrew, > > >>>>>>>> > > >>>>>>>>> -----Original Message----- > > >>>>>>>>> From: Andrew Rybchenko [mailto:arybche...@solarflare.com] > > >>>>>>>>> Sent: Friday, July 13, 2018 4:03 PM > > >>>>>>>>> To: Lu, Wenzhuo <wenzhuo...@intel.com>; dev@dpdk.org > > >>>>>>>>> Cc: Yigit, Ferruh <ferruh.yi...@intel.com>; Thomas Monjalon > > >>>>>>>>> <tho...@monjalon.net> > > >>>>>>>>> Subject: Re: [dpdk-dev] [PATCH v2] ethdev: fix device info > > >>>>>>>>> getting > > >>>>>>>>> > > >>>>>>>>> Hi, Wenzhuo, > > >>>>>>>>> > > >>>>>>>>> I'm sorry, but I have more even harder questions than the > > >>>>>>>>> previous > > >>>> one. > > >>>>>>>>> This questions are rather generic and mainly to ethdev > maintainers. > > >>>>>>>>> > > >>>>>>>>> On 13.07.2018 05:42, Wenzhuo Lu wrote: > > >>>>>>>>>> The device information cannot be gotten correctly before > > >>>>>>>>>> the configuration is set. Because on some NICs the > > >>>>>>>>>> information has dependence on the configuration. > > >>>>>>>>> Thinking about it I have the following question. Is it valid > > >>>>>>>>> behaviour of the dev_info if it changes after configuration? > > >>>>>>>>> I always thought that the primary goal of the dev_info is to > > >>>>>>>>> provide information to app about device capabilities to > > >>>>>>>>> allow app configure device and queues correctly. Now we see > > >>>>>>>>> the case when dev_info changes on configure. May be it is > > >>>>>>>>> acceptable, but it is really suspicious. If we accept it, it > > >>>>>>>>> should > be documented. > > >>>>>>>>> May be dev_info should be split into parts: part which is > > >>>>>>>>> persistent and part which may depend on device configuration. > > >>>>>>>> As I remember, the similar discussion has happened :) I've > > >>>>>>>> raised the similar suggestion like this. But we don’t make it > happen. > > >>>>>>>> The reason is, you see, this is the rte layer's behavior. So > > >>>>>>>> the user doesn't have to know it. From APP's PoV, it inputs > > >>>>>>>> the configuration, it calls this API "rte_eth_dev_configure". > > >>>>>>>> It doesn't know the configuration is copied before getting the > info or not. > > >>>>>>>> So, to my opinion, we can still keep the behavior. We only > > >>>>>>>> need to split it into parts when we do see the case that cannot > make it. > > >>>>>>> Maybe I talked too much about the patch. Think about it again. > > >>>>>>> Your comments is about how to use the APIs, > > >>>>>>> rte_eth_dev_info_get, > > >>>>>> rte_eth_dev_configure. To my opinion, rte_eth_dev_info_get is > > >>>>>> just to get the info. It can be called anywhere, before > > >>>>>> configuration or after. It's reasonable the info changes with the > configuration changing. > > >>>>>>> But we do have something missing, like, > > >>>>>>> rte_eth_dev_capability_get which > > >>>>>> should be stable. APP can use this API to get the necessary > > >>>>>> info before configuration. > > >>>>>>> A question, maybe a little divergent thinking, that APP should > > >>>>>>> have some > > >>>>>> intelligence to handle the capability automatically. So getting > > >>>>>> the capability is not so good and effective, looks like we > > >>>>>> still need the human > > >>>> involvement. > > >>>>>> Maybe that the reason currently we suppose APP know the > > >>>>>> capability from the paper copies, examples... > > >>>>>> > > >>>>>> I am not sure to understand all the sentences. > > >>>>>> But I agree that we should take a decision about the stability > > >>>>>> of these > > >>>> infos. > > >>>>>> Either infos cannot change after probing, or we must document > > >>>>>> that the app must request infos regularly (when?). > > >>>>> Sorry, I missed this mail. > > >>>>> > > >>>>> I have the concern that different NICs have different behavior. > > >>>>> One info > > >>>> can be stable on a NIC but dynamic on another. Considering this, > > >>>> we may better not splitting the rte_eth_dev_info_get to 2 APIs. > > >>>> And comparing with handling this in rte layer, maybe we can let every > NIC has its own decision. > > >>>>> I have an idea. Maybe we can add a parameter for potential > > >>>>> dynamic fields. Like, Changing uint16_t nb_rx_queues; to struct > > >>>>> nb_rx_queues { uint16_t value; bool stable; } > > >>>> May be it is just very bad example, but as I understand > > >>>> nb_rx_queues is mainly required to configure the device properly. > > >>>> Or should app configure, get new value, reconfigure again, get > > >>>> new value and so on and stop when previous is equal to the new one. > Yes, I dramatise and it sounds really bad. > > >>>> In any case it would over-complicate interface and no single app > > >>>> will do it correctly. > > >>> I think you're talking about max_rx_queues. APP can get that info > before configuration. Then configure rx queue number which is not larger > than it. That's enough. > > >>> nb_rx_queues should be the number which is configured by APP and > how many queues are actually used. To my opinion, it's mainly used by the > GUI to show the value to human being. > > >>> > > >>> BTW, max_rx_queues could be an good example that shows that > some parameters are stable on some NICs but not on other NICs. > > >>> Take Intel NICs for example (I don’t familiar with others.), normally > max_rx_queues is stable on PF. But on VF, as the max number is decided by > PF, it could be dynamic. When VF starts, it can get an default value from PF. > If it not enough, it can request a larger one from PF. If the number works, VF > can get a new number. > > >> "struct rte_eth_dev_info" is a little overloaded, it has: > > >> - static info, like *device > > >> - device limitations, max_*, *_lim > > >> - device capabilities, *_capa > > >> - suggested configurations, default_*conf > > >> - device configuration, nb_[r/t]x_queues > > >> - other, switch_info > > >> > > >> There is a concern that some values are dynamic, but this is not > > >> new, for example nb_rx/tx_queues can be changed by > > >> rte_eth_dev_rx/tx_queue_config() API and rte_eth_dev_info() output > will be changed. > > > > > > The example looks different to me. It is explicit changes directly > > > requested by the application. So, it is not a surprise that it changes. > > > > > >> For this patch suggested configuration changes based on some other > > >> config values looks ok as concept. > > >> So I think we can say after every configuration related API dev > > >> info can be changed. > > > > > > I think that saying that any configuration changes may result in any > > > changes in dev_info is hardly helpful. I'd suggest to be more specific. > > > Yes, it is harder and will have bugs, but at least it is helpful. > > > > Hi Andrew, Wenzhuo, > > > > Back to this patch, which fixes an actual defect, > > > > What do you think about: > > 1- Keep existing patch but extend it as, save the original "dev->data" > > and revert it back to this original data on all error path. > > 2- Update rte_eth_dev_info() API document and say default > > configuration can be changed based on other config fields. So this > > reduces the scope of things can change in dev_info. > > I think we are doing too much juggling with data in ethdev layer. > All these things should be the responsibility of the PMD. > My radical proposal would be to remove rte_eth_dev_info and integrate all > the data into rte_eth_dev_data. > Sorry for missing this discussion. It's a good discussion about how to optimize the rte_eth. But I have to say that above discussion can reach a huge reconsitution of the rte_eth and impact every PMD. Is that fair? This patch is only try to revert a bad commit as we already find bug. As I remember, at the beginning, Andrew said the discussion may not about the patch but generic. So could we just tell if this patch itself OK at first? Thanks.
