On Wed, Mar 6, 2013 at 1:37 PM, Sjur Brændeland <sjurbr@xxxxxxxxx> wrote: > On Wed, Mar 6, 2013 at 1:16 PM, Ohad Ben-Cohen <ohad@xxxxxxxxxx> wrote: >> On Wed, Mar 6, 2013 at 12:50 PM, Sjur Brændeland <sjur@xxxxxxxxxxxxxx> wrote: >>> The caif_virtio driver is using both host and guest ring sides, host side >>> rings in RX direction and guest side rings in TX direction. The reason >>> behind this is to enable zero-copy on the producer sides. >>> (For details see recent discussion with Ohad "Wrappers for vringh" >> >> FWIW, I'm not convinced that host side rings are necessary for >> zero-copy - you could always just pass pointers to your huge data >> inside buffers posted by guest side rings. When I read this again I realized that I missed your point regarding passing pointers inside buffers completely. My rambling below argued against using the buffers provided in the available ring as a replacement of the modem internal allocator. Sorry for the confusion. I haven't really spent time thinking through the implication of the alternative of passing buffer pointers inside buffers posted by guest side rings. But it seems to me that there would be some issues related to returning consumed buffers back if you use the rings in this way. Thanks, Sjur > Well, to do that for CAIF you would have to integrate virtio buffer handling > deep into the lower layer of the modems 3GPP stack so that the 3GPP stack > could take buffers from the available ring. > > From the outside point of view, perhaps this sounds doable, but in reality you > wouldn't get any Network Signalling engineers implementing the 3GPP stack > to buy into that. > > Another issue is that our modem also support other interface technologies > such as USB and HSI. It simply doesn't make sense to enforce virtio rings > internally if virtio isn't otherwise used on the modem. > > Without host side rings we simply wouldn't be able to implement zero-copy > in the RX direction for the STE-modem. > > Regards, > Sjur > >> >> That said, I do believe that mixing guest side and host side rings may >> simplify the overall solution in some cases, especially in more >> complex multi core scenarios (where several cores all communicate with >> each other). _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
