26/10/2019 11:23, Wang, Haiyue: > From: Thomas Monjalon [mailto:tho...@monjalon.net] > > 26/10/2019 06:40, Wang, Haiyue: > > > From: Thomas Monjalon [mailto:tho...@monjalon.net] > > > > 25/10/2019 18:02, Jerin Jacob: > > > > > On Fri, Oct 25, 2019 at 9:15 PM Thomas Monjalon <tho...@monjalon.net> > > > > > wrote: > > > > > > 25/10/2019 16:08, Ferruh Yigit: > > > > > > > On 10/25/2019 10:36 AM, Thomas Monjalon wrote: > > > > > > > > 15/10/2019 09:51, Haiyue Wang: > > > > > > > >> Some PMDs have more than one RX/TX burst paths, add the ethdev > > > > > > > >> API > > > > > > > >> that allows an application to retrieve the mode information > > > > > > > >> about > > > > > > > >> Rx/Tx packet burst such as Scalar or Vector, and Vector > > > > > > > >> technology > > > > > > > >> like AVX2. > > > > > > > > > > > > > > > > I missed this patch. I and Andrew, maintainers of ethdev, were > > > > > > > > not CC'ed. > > > > > > > > Ferruh, I would expect to be Cc'ed and/or get a notification > > > > > > > > before merging. > > > > > > > > > > > > > > It has been discussed in the mail list and went through multiple > > > > > > > discussions, > > > > > > > patch is out since the August, +1 to cc all maintainers I missed > > > > > > > that part, > > > > > > > but when the patch is reviewed and there is no objection, why > > > > > > > block the merge? > > > > > > > > > > > > I'm not saying blocking the merge. > > > > > > My bad is that I missed the patch and I am asking for help with a > > > > > > notification > > > > > > in this case. Same for Andrew I guess. > > > > > > Note: it is merged in master and I am looking to improve this > > > > > > feature. > > > > > > > > > > > > >> +/** > > > > > > > >> + * Ethernet device RX/TX queue packet burst mode information > > > > > > > >> structure. > > > > > > > >> + * Used to retrieve information about packet burst mode > > > > > > > >> setting. > > > > > > > >> + */ > > > > > > > >> +struct rte_eth_burst_mode { > > > > > > > >> + uint64_t options; > > > > > > > >> +}; > > > > > > > > > > > > > > > > Why a struct for an integer? > > > > > > > > > > > > > > Again by a request from me, to not need to break the API if we > > > > > > > need to add more > > > > > > > thing in the future. > > > > > > > > > > > > I would replace it with a string. This is the most flexible API. > > > > > > > > > > IMO, Probably, best of both worlds make a good option here, > > > > > as Haiyue suggested if we have an additional dev_specific[1] in > > > > > structure. > > > > > and when a pass to the application, let common code make final string > > > > > as > > > > > (options flags to string + dev_specific) > > > > > > > > > > options flag can be zero if PMD does not have any generic flags nor > > > > > interested in such a scheme. > > > > > Generic flags will help at least to have some common code. > > > > > > > > > > [1] > > > > > struct rte_eth_burst_mode { > > > > > uint64_t options; > > > > > char dev_specific[128]; /* PMD has specific burst mode > > > > > information */ > > > > > }; > > > > > > > > I really don't see how we can have generic flags. > > > > The flags which are proposed are just matching > > > > the functions implemented in Intel PMDs. > > > > And this is a complicate solution. > > > > Why not just returning a name for the selected Rx/Tx mode? > > > > > > Intel PMDs use the *generic* methods like x86 SSE, AVX2, ARM NEON, PPC > > > ALTIVEC, > > > 'dev->data->scattered_rx' etc for the target : "DPDK is the Data Plane > > > Development Kit > > > that consists of libraries to accelerate packet processing workloads > > > running on a wide > > > variety of CPU architectures." > > > > How RTE_ETH_BURST_SCATTERED and RTE_ETH_BURST_BULK_ALLOC are generic? > > They just match some features of the Intel PMDs. > > Why not exposing other optimizations of the Rx/Tx implementations? > > You totally missed the point of generic burst mode description. > > > > > If understand these new experimental APIs from above, then bit options is > > > the best, > > > and we didn't invent new words to describe them, just from the CPU & > > > other *generic* > > > technology. And the application can loop to check which kind of burst is > > > running by > > > just simple bit test. > > > > > > If PMDs missed these, they can update them in future roadmaps to enhance > > > their PMDs, > > > like MLX5 supports ARM NEON, x86 SSE. > > > > I have no word! > > You really think other PMDs should learn from Intel how to "enhance" their > > PMD? > > You talk about mlx5, did you look at its code? Did you see the burst modes > > depending on which specific hardware path is used (MPRQ, EMPW, inline)? > > Or depending on which offloads are handled? > > > > Again, the instruction set used by the function is a small part > > of the burst mode optimization. > > > > So you did not reply to my question: > > Why not just returning a name for the selected Rx/Tx mode? > > In fact, RFC v1/v2 returns the *name*, but the *name* is hard for > application to do further processing, strcmp, strstr ? Not so nice > for C code, and it is not so standard, So switch it to bit definition.
Again, please answer my question: why do you need it? I think it is just informative, that's why a string should be enough. I am clearly against the bitmap because it is way too much restrictive. I disagree that knowing it is using AVX2 or AVX512 is so interesting. What you would like to know is whether it is processing packets 4 by 4, for instance, or to know which offload is supported, or what hardware trick is used in the datapath design. There are so many options in a datapath design that it cannot be represented with a bitmap. And it makes no sense to have some design criterias more important than others. I Cc an Intel architect (Edwin) who could explain you how much a datapath design is more complicate than just using AVX instructions. > If the API is not bad, but the data is not so good, then accept below ? ;-) No, the API is bad.
