netdev - [PATCH net-next v2 3/4] bpf: test_run: Fix cacheline alignment of live XDP frame data structures

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Message-ID: <20240220210342.40267-4-toke@redhat.com>
Date: Tue, 20 Feb 2024 22:03:40 +0100
From: Toke Høiland-Jørgensen <toke@...hat.com>
To: Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...gle.com>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>,
	Jesper Dangaard Brouer <hawk@...nel.org>
Cc: Toke Høiland-Jørgensen <toke@...hat.com>,
	Alexander Lobakin <aleksander.lobakin@...el.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Paolo Abeni <pabeni@...hat.com>,
	bpf@...r.kernel.org,
	netdev@...r.kernel.org
Subject: [PATCH net-next v2 3/4] bpf: test_run: Fix cacheline alignment of live XDP frame data structures

The live XDP frame code in BPF_PROG_RUN suffered from suboptimal cache
line placement due to the forced cache line alignment of struct
xdp_rxq_info. Rearrange things so we don't waste a whole cache line on
padding, and also add explicit alignment to the data_hard_start field in
the start-of-page data structure we use for the data pages.

Reviewed-by: Alexander Lobakin <aleksander.lobakin@...el.com>
Tested-by: Alexander Lobakin <aleksander.lobakin@...el.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
---
 net/bpf/test_run.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index 60a36a4df3e1..485084c302b2 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -113,12 +113,12 @@ struct xdp_page_head {
 		/* ::data_hard_start starts here */
 		DECLARE_FLEX_ARRAY(struct xdp_frame, frame);
 		DECLARE_FLEX_ARRAY(u8, data);
-	};
+	} ____cacheline_aligned;
 };
 
 struct xdp_test_data {
-	struct xdp_buff *orig_ctx;
 	struct xdp_rxq_info rxq;
+	struct xdp_buff *orig_ctx;
 	struct net_device *dev;
 	struct xdp_frame **frames;
 	struct sk_buff **skbs;
-- 
2.43.0