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From: Jesper Dangaard Brouer <brouer@redhat.com>
To: sameehj@amazon.com
Cc: "Jesper Dangaard Brouer" <brouer@redhat.com>,
	netdev@vger.kernel.org, bpf@vger.kernel.org,
	"Toke Høiland-Jørgensen" <toke@redhat.com>,
	"Daniel Borkmann" <borkmann@iogearbox.net>,
	"Alexei Starovoitov" <alexei.starovoitov@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	"John Fastabend" <john.fastabend@gmail.com>,
	"Alexander Duyck" <alexander.duyck@gmail.com>,
	"Jeff Kirsher" <jeffrey.t.kirsher@intel.com>,
	"David Ahern" <dsahern@gmail.com>,
	"Ilias Apalodimas" <ilias.apalodimas@linaro.org>,
	"Lorenzo Bianconi" <lorenzo@kernel.org>,
	"Saeed Mahameed" <saeedm@mellanox.com>,
	"Tariq Toukan" <tariqt@mellanox.com>
Subject: [PATCH net-next v4 08/33] xdp: cpumap redirect use frame_sz and increase skb_tailroom
Date: Thu, 14 May 2020 12:49:38 +0200	[thread overview]
Message-ID: <158945337822.97035.13557959180460986059.stgit@firesoul> (raw)
In-Reply-To: <158945314698.97035.5286827951225578467.stgit@firesoul>

Knowing the memory size backing the packet/xdp_frame data area, and
knowing it already have reserved room for skb_shared_info, simplifies
using build_skb significantly.

With this change we no-longer lie about the SKB truesize, but more
importantly a significant larger skb_tailroom is now provided, e.g. when
drivers uses a full PAGE_SIZE. This extra tailroom (in linear area) can be
used by the network stack when coalescing SKBs (e.g. in skb_try_coalesce,
see TCP cases where tcp_queue_rcv() can 'eat' skb).

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
 kernel/bpf/cpumap.c |   21 +++------------------
 1 file changed, 3 insertions(+), 18 deletions(-)

diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index 3fe0b006d2d2..a71790dab12d 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -162,25 +162,10 @@ static struct sk_buff *cpu_map_build_skb(struct bpf_cpu_map_entry *rcpu,
 	/* Part of headroom was reserved to xdpf */
 	hard_start_headroom = sizeof(struct xdp_frame) +  xdpf->headroom;
 
-	/* build_skb need to place skb_shared_info after SKB end, and
-	 * also want to know the memory "truesize".  Thus, need to
-	 * know the memory frame size backing xdp_buff.
-	 *
-	 * XDP was designed to have PAGE_SIZE frames, but this
-	 * assumption is not longer true with ixgbe and i40e.  It
-	 * would be preferred to set frame_size to 2048 or 4096
-	 * depending on the driver.
-	 *   frame_size = 2048;
-	 *   frame_len  = frame_size - sizeof(*xdp_frame);
-	 *
-	 * Instead, with info avail, skb_shared_info in placed after
-	 * packet len.  This, unfortunately fakes the truesize.
-	 * Another disadvantage of this approach, the skb_shared_info
-	 * is not at a fixed memory location, with mixed length
-	 * packets, which is bad for cache-line hotness.
+	/* Memory size backing xdp_frame data already have reserved
+	 * room for build_skb to place skb_shared_info in tailroom.
 	 */
-	frame_size = SKB_DATA_ALIGN(xdpf->len + hard_start_headroom) +
-		SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+	frame_size = xdpf->frame_sz;
 
 	pkt_data_start = xdpf->data - hard_start_headroom;
 	skb = build_skb_around(skb, pkt_data_start, frame_size);



  parent reply	other threads:[~2020-05-14 10:49 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-14 10:48 [PATCH net-next v4 00/33] XDP extend with knowledge of frame size Jesper Dangaard Brouer
2020-05-14 10:49 ` [PATCH net-next v4 01/33] xdp: add frame size to xdp_buff Jesper Dangaard Brouer
2020-05-14 10:49 ` [PATCH net-next v4 02/33] bnxt: add XDP frame size to driver Jesper Dangaard Brouer
2020-05-14 10:49 ` [PATCH net-next v4 03/33] sfc: add XDP frame size Jesper Dangaard Brouer
2020-05-14 10:49 ` [PATCH net-next v4 04/33] mvneta: add XDP frame size to driver Jesper Dangaard Brouer
2020-05-14 10:49 ` [PATCH net-next v4 05/33] net: netsec: Add support for XDP frame size Jesper Dangaard Brouer
2020-05-14 10:49 ` [PATCH net-next v4 06/33] net: XDP-generic determining " Jesper Dangaard Brouer
2020-05-14 10:49 ` [PATCH net-next v4 07/33] xdp: xdp_frame add member frame_sz and handle in convert_to_xdp_frame Jesper Dangaard Brouer
2020-05-14 10:49 ` Jesper Dangaard Brouer [this message]
2020-05-14 10:49 ` [PATCH net-next v4 09/33] veth: adjust hard_start offset on redirect XDP frames Jesper Dangaard Brouer
2020-05-14 10:49 ` [PATCH net-next v4 10/33] veth: xdp using frame_sz in veth driver Jesper Dangaard Brouer
2020-05-14 10:49 ` [PATCH net-next v4 11/33] dpaa2-eth: add XDP frame size Jesper Dangaard Brouer
2020-05-14 10:49 ` [PATCH net-next v4 12/33] hv_netvsc: add XDP frame size to driver Jesper Dangaard Brouer
2020-05-14 10:50 ` [PATCH net-next v4 13/33] qlogic/qede: " Jesper Dangaard Brouer
2020-05-14 10:50 ` [PATCH net-next v4 14/33] net: ethernet: ti: add XDP frame size to driver cpsw Jesper Dangaard Brouer
2020-05-14 10:50 ` [PATCH net-next v4 15/33] ena: add XDP frame size to amazon NIC driver Jesper Dangaard Brouer
2020-05-14 10:50 ` [PATCH net-next v4 16/33] mlx4: add XDP frame size and adjust max XDP MTU Jesper Dangaard Brouer
2020-05-14 10:50 ` [PATCH net-next v4 17/33] net: thunderx: add XDP frame size Jesper Dangaard Brouer
2020-05-14 10:50 ` [PATCH net-next v4 18/33] nfp: add XDP frame size to netronome driver Jesper Dangaard Brouer
2020-05-14 10:50 ` [PATCH net-next v4 19/33] tun: add XDP frame size Jesper Dangaard Brouer
2020-05-14 10:50 ` [PATCH net-next v4 20/33] vhost_net: also populate " Jesper Dangaard Brouer
2020-05-14 10:50 ` [PATCH net-next v4 21/33] virtio_net: add XDP frame size in two code paths Jesper Dangaard Brouer
2020-05-14 10:50 ` [PATCH net-next v4 22/33] ixgbe: fix XDP redirect on archs with PAGE_SIZE above 4K Jesper Dangaard Brouer
2020-05-14 10:50 ` [PATCH net-next v4 23/33] ixgbe: add XDP frame size to driver Jesper Dangaard Brouer
2020-05-14 10:50 ` [PATCH net-next v4 24/33] ixgbevf: add XDP frame size to VF driver Jesper Dangaard Brouer
2020-05-14 10:51 ` [PATCH net-next v4 25/33] i40e: add XDP frame size to driver Jesper Dangaard Brouer
2020-05-14 10:51 ` [PATCH net-next v4 26/33] ice: " Jesper Dangaard Brouer
2020-05-14 10:51 ` [PATCH net-next v4 27/33] xdp: for Intel AF_XDP drivers add XDP frame_sz Jesper Dangaard Brouer
2020-05-14 10:51 ` [PATCH net-next v4 28/33] mlx5: rx queue setup time determine frame_sz for XDP Jesper Dangaard Brouer
2020-05-14 10:51 ` [PATCH net-next v4 29/33] xdp: allow bpf_xdp_adjust_tail() to grow packet size Jesper Dangaard Brouer
2020-05-14 10:51 ` [PATCH net-next v4 30/33] xdp: clear grow memory in bpf_xdp_adjust_tail() Jesper Dangaard Brouer
2020-05-14 10:51 ` [PATCH net-next v4 31/33] bpf: add xdp.frame_sz in bpf_prog_test_run_xdp() Jesper Dangaard Brouer
2020-05-17  4:02   ` unstable xdp tests. Was: " Alexei Starovoitov
2020-05-18  9:52     ` Jesper Dangaard Brouer
2020-05-18 10:30       ` Jesper Dangaard Brouer
2020-05-18 19:19         ` Andrii Nakryiko
2020-05-14 10:51 ` [PATCH net-next v4 32/33] selftests/bpf: adjust BPF selftest for xdp_adjust_tail Jesper Dangaard Brouer
2020-05-14 10:51 ` [PATCH net-next v4 33/33] selftests/bpf: xdp_adjust_tail add grow tail tests Jesper Dangaard Brouer
2020-05-15  4:52 ` [PATCH net-next v4 00/33] XDP extend with knowledge of frame size Alexei Starovoitov

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