On Fri, Oct 4, 2024 at 10:47 AM Mina Almasry <almasrymina@xxxxxxxxxx> wrote: > > On Thu, Oct 3, 2024 at 12:33 PM Taehee Yoo <ap420073@xxxxxxxxx> wrote: > > > > On Fri, Oct 4, 2024 at 3:25 AM Mina Almasry <almasrymina@xxxxxxxxxx> wrote: > > > > > > On Thu, Oct 3, 2024 at 9:07 AM Taehee Yoo <ap420073@xxxxxxxxx> wrote: > > > > > > > > The tcp-data-split-thresh option configures the threshold value of > > > > the tcp-data-split. > > > > If a received packet size is larger than this threshold value, a packet > > > > will be split into header and payload. > > > > > > Why do you need this? devmem TCP will always not work with unsplit > > > packets. Seems like you always want to set thresh to 0 to support > > > something like devmem TCP. > > > > > > Why would the user ever want to configure this? I can't think of a > > > scenario where the user wouldn't want packets under X bytes to be > > > unsplit. > > > > I totally understand what you mean, > > Yes, tcp-data-split is zerocopy friendly option but as far as I know, > > this option is not only for the zerocopy usecase. > > So, If users enable tcp-data-split, they would assume threshold is 0. > > But there are already NICs that have been supporting tcp-data-split > > enabled by default. > > bnxt_en's default value is 256bytes. > > If we just assume the tcp-data-split-threshold to 0 for all cases, > > it would change the default behavior of bnxt_en driver(maybe other drivers too) > > for the not zerocopy case. > > Jakub pointed out the generic case, not only for zerocopy usecase > > in the v1 and I agree with that opinion. > > https://lore.kernel.org/netdev/20240906183844.2e8226f3@xxxxxxxxxx/ > > I see, thanks. The ability to tune the threshold to save some pcie > bandwidth is interesting. Not sure how much it would matter in > practice. I guess if you're receiving _lots_ of small packets then it > could be critical. > > Sounds good then, please consider adding Jakub's reasoning for why > tuning this could be valuable to the commit message for future > userspace readers that wonder why to set this. Okay, I will add an explanation of this feature to commit message in v4 patch. Thanks a lot! Taehee Yoo > > -- > Thanks, > Mina
