On 16-09-09 06:04 PM, Tom Herbert wrote: > On Fri, Sep 9, 2016 at 5:01 PM, John Fastabend <john.fastab...@gmail.com> > wrote: >> On 16-09-09 04:44 PM, Tom Herbert wrote: >>> On Fri, Sep 9, 2016 at 2:29 PM, John Fastabend <john.fastab...@gmail.com> >>> wrote: >>>> e1000 supports a single TX queue so it is being shared with the stack >>>> when XDP runs XDP_TX action. This requires taking the xmit lock to >>>> ensure we don't corrupt the tx ring. To avoid taking and dropping the >>>> lock per packet this patch adds a bundling implementation to submit >>>> a bundle of packets to the xmit routine. >>>> >>>> I tested this patch running e1000 in a VM using KVM over a tap >>>> device using pktgen to generate traffic along with 'ping -f -l 100'. >>>> >>> Hi John, >>> >>> How does this interact with BQL on e1000? >>> >>> Tom >>> >> >> Let me check if I have the API correct. When we enqueue a packet to >> be sent we must issue a netdev_sent_queue() call and then on actual >> transmission issue a netdev_completed_queue(). >> >> The patch attached here missed a few things though. >> >> But it looks like I just need to call netdev_sent_queue() from the >> e1000_xmit_raw_frame() routine and then let the tx completion logic >> kick in which will call netdev_completed_queue() correctly. >> >> I'll need to add a check for the queue state as well. So if I do these >> three things, >> >> check __QUEUE_STATE_XOFF before sending >> netdev_sent_queue() -> on XDP_TX >> netdev_completed_queue() >> >> It should work agree? Now should we do this even when XDP owns the >> queue? Or is this purely an issue with sharing the queue between >> XDP and stack. >> > But what is the action for XDP_TX if the queue is stopped? There is no > qdisc to back pressure in the XDP path. Would we just start dropping > packets then?
Yep that is what the patch does if there is any sort of error packets get dropped on the floor. I don't think there is anything else that can be done. > > Tom > >> .John >>
