netdev - [RFC PATCH bpf-next 13/14] i40e: prefetch xdp->data before running XDP prog

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Date:   Tue, 13 Aug 2019 21:05:57 +0900
From:   Toshiaki Makita <toshiaki.makita1@...il.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>
Cc:     Toshiaki Makita <toshiaki.makita1@...il.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        William Tu <u9012063@...il.com>
Subject: [RFC PATCH bpf-next 13/14] i40e: prefetch xdp->data before running XDP prog

XDP progs are likely to read/write xdp->data.
This improves the performance of xdp_flow.
This is included in this series just to demonstrate to what extent
xdp_flow performance can increase.

Signed-off-by: Toshiaki Makita <toshiaki.makita1@...il.com>
---
 drivers/net/ethernet/intel/i40e/i40e_txrx.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index f162252..ea775ae 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -2207,6 +2207,7 @@ static struct sk_buff *i40e_run_xdp(struct i40e_ring *rx_ring,
 	if (!xdp_prog)
 		goto xdp_out;
 
+	prefetchw(xdp->data);
 	prefetchw(xdp->data_hard_start); /* xdp_frame write */
 
 	act = bpf_prog_run_xdp(xdp_prog, xdp);
-- 
1.8.3.1