On Tue, Nov 22, 2016 at 12:17:40AM -0800, John Fastabend wrote: > On 16-11-21 03:13 PM, Michael S. Tsirkin wrote: > > On Sat, Nov 19, 2016 at 06:51:04PM -0800, John Fastabend wrote: > >> XDP requires using isolated transmit queues to avoid interference > >> with normal networking stack (BQL, NETDEV_TX_BUSY, etc). This patch > >> adds a XDP queue per cpu when a XDP program is loaded and does not > >> expose the queues to the OS via the normal API call to > >> netif_set_real_num_tx_queues(). This way the stack will never push > >> an skb to these queues. > >> > >> However virtio/vhost/qemu implementation only allows for creating > >> TX/RX queue pairs at this time so creating only TX queues was not > >> possible. And because the associated RX queues are being created I > >> went ahead and exposed these to the stack and let the backend use > >> them. This creates more RX queues visible to the network stack than > >> TX queues which is worth mentioning but does not cause any issues as > >> far as I can tell. > >> > >> Signed-off-by: John Fastabend <john.r.fastab...@intel.com> > > > > FYI what's supposed to happen is packets from the same > > flow going in the reverse direction will go on the > > same queue. > > > > This might come in handy when implementing RX XDP. > > > > Yeah but if its the first packet not part of a flow then presumably it > can pick any queue but its worth keeping in mind certainly. > > .John
Oh I agree, absolutely. This was just a FYI in case it comes useful as an optimization down the road. -- MST
