On Thu, 2016-11-17 at 09:16 +0100, Jesper Dangaard Brouer wrote: > > I noticed there is a Send-Q, and the perf-top2 is _raw_spin_lock, which > looks like it comes from __dev_queue_xmit(), but we know from > experience that this stall is actually caused by writing the > tailptr/doorbell in the HW. Thus, this could benefit a lot from > bulk/xmit_more into the qdisc layer.
The Send-Q is there because of TX-completions being delayed a bit, because of IRQ mitigation. (ethtool -c eth0) It happens even if you do not have a qdisc in the first place. And we do have xmit_more in the qdisc layer already.
