[Intel-wired-lan] [PATCH net-next v2 1/3] i40e: optimize AF_XDP Tx completion path

[Bowers, AndrewX]

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces at osuosl.org> On Behalf Of
> Magnus Karlsson
> Sent: Tuesday, June 23, 2020 2:44 AM
> To: Karlsson, Magnus <magnus.karlsson at intel.com>; Topel, Bjorn
> <bjorn.topel at intel.com>; intel-wired-lan at lists.osuosl.org; Kirsher, Jeffrey T
> <jeffrey.t.kirsher at intel.com>; Samudrala, Sridhar
> <sridhar.samudrala at intel.com>
> Cc: maciejromanfijalkowski at gmail.com; Fijalkowski, Maciej
> <maciej.fijalkowski at intel.com>; netdev at vger.kernel.org
> Subject: [Intel-wired-lan] [PATCH net-next v2 1/3] i40e: optimize AF_XDP Tx
> completion path
> 
> Improve the performance of the AF_XDP zero-copy Tx completion path.
> When there are no XDP buffers being sent using XDP_TX or XDP_REDIRECT,
> we do not have go through the SW ring to clean up any entries since the
> AF_XDP path does not use these. In these cases, just fast forward the next-
> to-use counter and skip going through the SW ring. The limit on the
> maximum number of entries to complete is also removed since the algorithm
> is now O(1). To simplify the code path, the maximum number of entries to
> complete for the XDP path is therefore also increased from 256 to 512 (the
> default number of Tx HW descriptors). This should be fine since the
> completion in the XDP path is faster than in the SKB path that has 256 as the
> maximum number.
> 
> This patch provides around 4% throughput improvement for the l2fwd
> application in xdpsock on my machine.
> 
> Signed-off-by: Magnus Karlsson <magnus.karlsson at intel.com>
> ---
>  drivers/net/ethernet/intel/i40e/i40e_txrx.c |  3 +-
> drivers/net/ethernet/intel/i40e/i40e_txrx.h |  1 +
> drivers/net/ethernet/intel/i40e/i40e_xsk.c  | 43 +++++++++++++++----------
> ----  drivers/net/ethernet/intel/i40e/i40e_xsk.h  |  3 +-
>  4 files changed, 27 insertions(+), 23 deletions(-)

Tested-by: Andrew Bowers <andrewx.bowers at intel.com>