On Tue, 24 Jan 2017 14:39:19 -0800 Eric Dumazet <eric.duma...@gmail.com> wrote:
> On Tue, 2017-01-24 at 13:06 -0800, Stephen Hemminger wrote: > > To improve performance, netvsc can call network stack directly and > > avoid the local backlog queue. This is safe since incoming packets are > > handled in softirq context already because the receive function > > callback is called from a tasklet. > > Is this tasklet implementing a limit or something ? The ring only holds a fixed amount of data so there is a limit but it is quite large. > > netif_rx() queues packets to the backlog, which is processed later by > net_rx_action() like other NAPI, with limit of 64 packets per round. Since netvsc_receive has to copy all incoming data it is a bottleneck unto itself. By the time net_rx_action is invoked the cache is stale. > > Calling netif_receive_skb() means you can escape this ability to fairly > distribute the cpu cycles among multiple NAPI. > > I do not see range_cnt being capped in netvsc_receive() There is no cap. NAPI is coming and will help.
