Re: [net-next PATCH v3 7/8] epoll: Add busy poll support to epoll with socket fds.

[Eric Dumazet]

On Fri, 2017-03-24 at 10:08 -0700, Alexander Duyck wrote:
> From: Sridhar Samudrala <sridhar.samudrala@xxxxxxxxx>
> 
> This patch adds busy poll support to epoll. The implementation is meant to
> be opportunistic in that it will take the NAPI ID from the last socket
> that is added to the ready list that contains a valid NAPI ID and it will
> use that for busy polling until the ready list goes empty.  Once the ready
> list goes empty the NAPI ID is reset and busy polling is disabled until a
> new socket is added to the ready list.
> 
> In addition when we insert a new socket into the epoll we record the NAPI
> ID and assume we are going to receive events on it.  If that doesn't occur
> it will be evicted as the active NAPI ID and we will resume normal
> behavior.
> 
> An application can use SO_INCOMING_CPU or SO_REUSEPORT_ATTACH_C/EBPF socket
> options to spread the incoming connections to specific worker threads
> based on the incoming queue. This enables epoll for each worker thread
> to have only sockets that receive packets from a single queue. So when an
> application calls epoll_wait() and there are no events available to report,
> busy polling is done on the associated queue to pull the packets.
> 
> Signed-off-by: Sridhar Samudrala <sridhar.samudrala@xxxxxxxxx>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxx>
> ---
>  fs/eventpoll.c |   93 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 93 insertions(+)

Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>