On Wed, 2022-08-17 at 11:48 +0100, Pavel Begunkov wrote: > On 8/16/22 09:37, Dylan Yudaken wrote: > > On Tue, 2022-08-16 at 08:42 +0100, Pavel Begunkov wrote: > > > Considering limited amount of slots some users struggle with > > > registration time notification tag assignment as it's hard to > > > manage > > > notifications using sequence numbers. Add a simple feature that > > > copies > > > sqe->user_data of a send(+flush) request into the notification > > > CQE it > > > flushes (and only when it's flushes). > > > > I think for this to be useful I think it would also be needed to > > have > > flags on the generated CQE. > > > > If there are more CQEs coming for the same request it should have > > IORING_CQE_F_MORE set. Otherwise user space would not be able to > > know > > if it is able to reuse local data. > > If you want to have: > > expect_more = cqe->flags & IORING_CQE_F_MORE; > > Then in the current form you can perfectly do that with > > // MSG_WAITALL > expect_more = (cqe->res == io_len); > // !MSG_WAITALL, > expect_more = (cqe->res >= 0); > > But might be more convenient to have IORING_CQE_F_MORE set, > one problem is a slight change of (implicit) semantics, i.e. > we don't execute linked requests when filling a IORING_CQE_F_MORE > CQE + CQE ordering implied from that. > > It's maybe worth to not rely on the link failing concept for > deciding whether to flush or not. Is the ordering guaranteed then to be <send cqe>, <notif cqe>? If so I would put the IORING_CQE_F_MORE more as a nice to have for consistency with other ops > > > > Additionally it would need to provide a way of disambiguating the > > send > > CQE with the flush CQE. > > Do you mean like IORING_CQE_F_NOTIF from 1/2? > Apologies - I missed that
