Hi Jerin, > -----Original Message----- > From: Jerin Jacob <jerinjac...@gmail.com> > Sent: Monday, December 23, 2019 5:20 PM > To: Gavin Hu <gavin...@arm.com> > Cc: dpdk-dev <dev@dpdk.org>; nd <n...@arm.com>; David Marchand > <david.march...@redhat.com>; tho...@monjalon.net; > rasl...@mellanox.com; maxime.coque...@redhat.com; > tiwei....@intel.com; hemant.agra...@nxp.com; jer...@marvell.com; > Pavan Nikhilesh <pbhagavat...@marvell.com>; Honnappa Nagarahalli > <honnappa.nagaraha...@arm.com>; Ruifeng Wang > <ruifeng.w...@arm.com>; Phil Yang <phil.y...@arm.com>; Joyce Kong > <joyce.k...@arm.com>; Steve Capper <steve.cap...@arm.com> > Subject: Re: [dpdk-dev] [PATCH v2 1/3] eal/arm64: relax the io barrier for > aarch64 > > On Mon, Dec 23, 2019 at 2:44 PM Gavin Hu <gavin...@arm.com> wrote: > > > > Hi Jerin, > > Hi Gavin, > > > > > I think we are on the same page with regard to the problem, and the > situations, thanks for illuminating the historical background of the two > barriers. > > About the solution, I added inline comments. > > > It will be optimization only when if we are changing in the fast path. > > > In the slow path, it does not matter. > > > I think, the First step should be to use rte_cio_* wherever it is > > > coherent memory used in _fast path_. I think, Almost every driver > > > fixed that. > > > > > > I am not against this patch(changing the slow path to use rte_cio* > > > from rte_io* and virtio changes associated with that). > > > If you are taking that patch, pay attention to all the drivers in the > > > tree which is using rte_io* for mixed access in slowpath. > > I see 30+ drivers has calling rte_io* directly or indirectly through > rte_write/read*. > > It is hard for me to figure out all the mixed accesses in these drivers, and > as you said, it makes no sense to change the _slow path_. > > > > How about we keep the old rte_io as is, and introduce 'fast path' version > of rte_io for new code use? > > Then in future, we may merge the two? > > Another reason about this proposal is maybe there is rte_io calling in the > fast path, but they are not mixed accesses and rte_cio is not suitable. > > Could you share more details about the case where fastpath + rte_io > needed + rte_cio is not suitable?
Here is an example for i40e, in the fast path, but only a pure io memory access. https://code.dpdk.org/dpdk/v19.11/source/drivers/net/i40e/i40e_rxtx.c#L1208 I wanted two variants of rte_io, because also x86 requires two as indicated here, one for no-WC and another for WC. http://inbox.dpdk.org/dev/20191204151916.12607-1-xiaoyun...@intel.com/T/#ea8bb1b4a378ab09baedbf95b4542bcb92f4a396f > > > > > Any thoughts? > > > > > > > > > But as the case in i40e, we must pay attention to where rte_cio was > > > missing but rescued by old rte_io(but not by new rte_io). > > > > > > > >
