On Fri, 2016-04-01 at 10:13 +0800, Jason Wang wrote:

The problem is we want to support busy polling for tun. This needs
napi_id to be passed to tun socket by sk_mark_napi_id() during
tun_net_xmit(). But before reaching this, XPS will set sender_cpu will
make us can't see correct napi_id.

Looks like napi_id should have precedence then ?

Only forwarding should allow the field to be cleared to allow XPS to do
its job.

Maybe skb_sender_cpu_clear() was removed too early (commit
64d4e3431e686dc37ce388ba531c4c4e866fb141)

Look, it is 8pm here, I am pretty sure a solution can be found,
but I am also need to take a break, I started at 3am today...