On Wed, Jan 25, 2017 at 5:33 AM, Oliver Hartkopp <socketcan@xxxxxxxxxxxx> wrote: > On 01/25/2017 10:39 AM, Hayes Wang wrote: >> >> Oliver Neukum [mailto:oneukum@xxxxxxxx] >>> >>> Sent: Wednesday, January 25, 2017 5:35 PM >> >> [...] >>> >>> looking at r8152 I noticed that it uses NAPI. I never considered >>> this for the generic USB networking code as you cannot disable >>> interrupts for USB. Is it still worth it? What are the benefits? >> >> >> You could use napi_gro_receive() and it influences the performance. > > > Another positive effect with NAPI is that you won't face out-of-order > ethernet frames as you get with non-NAPI drivers, e.g. ax88179_178a > > http://marc.info/?l=linux-can&m=148049063812807&w=2 > > We have the issue with CAN drivers where all USB drivers and >90% of the I/O > mapped drivers do not use NAPI. > > I wonder whether it makes sense to add NAPI to a driver which only has ONE > RX buffer ... but when searching for a solution for o-o-o frames I was > always pointed to NAPI. > > Regards, > Oliver > You could probably get around the o-o-o problem by enabling RPS for the interface. I have found that it works for me to do that in order to resolve o-o-o frames generated by VMs on virtual interfaces that can't use NAPI. - Alex -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
