On Mon, Jun 17, 2019 at 10:51:52AM +0200, David Marchand wrote: > On Mon, Jun 17, 2019 at 10:45 AM Ye Xiaolong <xiaolong...@intel.com> wrote: > > > On 06/17, David Marchand wrote: > > >On Mon, Jun 17, 2019 at 9:42 AM Xiaolong Ye <xiaolong...@intel.com> > > wrote: > > > > > >> This patch adds a new devarg to support the need_wakeup flag for Tx and > > >> fill rings, when this flag is set by the driver, it means that the > > >> userspace application has to explicitly wake up the kernel Rx or kernel > > Tx > > >> processing by issuing a syscall. Poll() can wake up both and sendto() or > > >> its alternatives will wake up Tx processing only. > > >> > > >> This feature is to provide efficient support for case that application > > and > > >> driver are executing on the same core. > > >> > > >> Signed-off-by: Xiaolong Ye <xiaolong...@intel.com> > > >> --- > > >> > > >> Original busy poll feature has morphed into need_wakeup flag in > > >> kernel side, the main purpose is the same, that is to support both > > >> application and driver executing on the same core efficiently. > > >> > > >> kernel side patchset can be found at netdev mailing list. > > >> > > >> > > https://lore.kernel.org/netdev/CAJ8uoz2szX=+jxxamyuvmvssmxzudqp6a8rjdqptioxbzwx...@mail.gmail.com/T/#t > > >> > > >> It is targeted for v5.3 > > >> > > > > > >- Is this really optional? Adding too many options is just a nightmare > > >later... > > > > Hmm, I think we can remove this option and alway turn the need_wakeup flag > > on > > since it provides better performance for 1 core case and doesn't downgrage > > the > > 2 core case performance. > > > > > > > >- I suppose this will break compilation with kernels that have af_xdp but > > >are < 5.3. > > > > Yes, that is true. It will break the compilation with early kernel, I feel > > it's > > sort of common issue, we enable some features in dpdk that's based on > > kernel > > features, then kernel side features keep evolving, we need to keep the > > pace, > > but it will hurt the compatiblity with the old kernel. > > > > What's dpdk's convention for handling this kind of case? Add some notes in > > doc > > to reminder the prerequisite or use the KERNEL_VERSION macro in code? > > > > Rather than a kernel version, you can check that XDP_USE_NEED_WAKEUP is > defined (present in the uapi kernel header). > +1 for this.
Also, since AF_XDP is still fairly new with ongoing development on the kernel side, I think it is reasonable to limit out PMD to only working with sufficiently updated kernels. Hopefully in 6 months or so, the feature set we need should be locked down and we can specify a fixed baseline requirement. /Bruce
