netdev - RE: [Intel-wired-lan] [PATCH bpf-next 6/6] i40e: use batched xsk Tx interfaces to increase performance

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Date:   Mon, 09 Nov 2020 13:10:59 -0800
From:   John Fastabend <john.fastabend@...il.com>
To:     Magnus Karlsson <magnus.karlsson@...il.com>,
        magnus.karlsson@...el.com, bjorn.topel@...el.com, ast@...nel.org,
        daniel@...earbox.net, netdev@...r.kernel.org,
        jonathan.lemon@...il.com
Cc:     maciejromanfijalkowski@...il.com, intel-wired-lan@...ts.osuosl.org,
        bpf@...r.kernel.org
Subject: RE: [Intel-wired-lan] [PATCH bpf-next 6/6] i40e: use batched xsk Tx
 interfaces to increase performance

Magnus Karlsson wrote:
> From: Magnus Karlsson <magnus.karlsson@...el.com>
> 
> Use the new batched xsk interfaces for the Tx path in the i40e driver
> to improve performance. On my machine, this yields a throughput
> increase of 4% for the l2fwd sample app in xdpsock. If we instead just
> look at the Tx part, this patch set increases throughput with above
> 20% for Tx.
> 
> Note that I had to explicitly loop unroll the inner loop to get to
> this performance level, by using a pragma. It is honored by both clang
> and gcc and should be ignored by versions that do not support
> it. Using the -funroll-loops compiler command line switch on the
> source file resulted in a loop unrolling on a higher level that
> lead to a performance decrease instead of an increase.
> 
> Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>
> ---
>  drivers/net/ethernet/intel/i40e/i40e_ethtool.c |   2 +-
>  drivers/net/ethernet/intel/i40e/i40e_main.c    |   4 +-
>  drivers/net/ethernet/intel/i40e/i40e_txrx.c    |  14 ++-
>  drivers/net/ethernet/intel/i40e/i40e_txrx.h    |   3 +-
>  drivers/net/ethernet/intel/i40e/i40e_xsk.c     | 127 ++++++++++++++++++-------
>  5 files changed, 110 insertions(+), 40 deletions(-)
> 

LGTM, although I mostly just reviewed the API usage. Maciej's seems like
a nice cleanup.

Acked-by: John Fastabend <john.fastabend@...il.com>