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, zorik@amazon.com,
akiyano@amazon.com, gtzalik@amazon.com,
"Toke Høiland-Jørgensen" <toke@toke.dk>,
"Daniel Borkmann" <borkmann@iogearbox.net>,
"Alexei Starovoitov" <alexei.starovoitov@gmail.com>,
"John Fastabend" <john.fastabend@gmail.com>,
"Alexander Duyck" <alexander.duyck@gmail.com>,
"Jeff Kirsher" <jeffrey.t.kirsher@intel.com>,
"David Ahern" <dsahern@gmail.com>,
"Willem de Bruijn" <willemdebruijn.kernel@gmail.com>,
"Ilias Apalodimas" <ilias.apalodimas@linaro.org>,
"Lorenzo Bianconi" <lorenzo@kernel.org>
Subject: [PATCH RFC v1 12/15] xdp: cpumap redirect use frame_sz and increase skb_tailroom
Date: Tue, 17 Mar 2020 18:30:08 +0100 [thread overview]
Message-ID: <158446620869.702578.7089227022464284959.stgit@firesoul> (raw)
In-Reply-To: <158446612466.702578.2795159620575737080.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>
---
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 70f71b154fa5..9c777ac4d4bd 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);
next prev parent reply other threads:[~2020-03-17 17:30 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-17 17:29 [PATCH RFC v1 00/15] XDP extend with knowledge of frame size Jesper Dangaard Brouer
2020-03-17 17:29 ` [PATCH RFC v1 01/15] xdp: add frame size to xdp_buff Jesper Dangaard Brouer
2020-03-17 20:42 ` Jakub Kicinski
2020-03-18 6:58 ` Jesper Dangaard Brouer
2020-03-17 17:29 ` [PATCH RFC v1 02/15] mvneta: add XDP frame size to driver Jesper Dangaard Brouer
2020-03-17 17:29 ` [PATCH RFC v1 03/15] bnxt: " Jesper Dangaard Brouer
2020-03-20 19:22 ` Andy Gospodarek
2020-03-23 14:18 ` Andy Gospodarek
2020-03-23 14:44 ` Jesper Dangaard Brouer
2020-03-17 17:29 ` [PATCH RFC v1 04/15] ixgbe: fix XDP redirect on archs with PAGE_SIZE above 4K Jesper Dangaard Brouer
2020-03-17 17:29 ` [PATCH RFC v1 05/15] ixgbe: add XDP frame size to driver Jesper Dangaard Brouer
2020-03-18 20:03 ` Maciej Fijalkowski
2020-03-18 21:23 ` Alexander Duyck
2020-03-20 21:44 ` Jesper Dangaard Brouer
2020-03-20 22:37 ` Alexander Duyck
2020-03-17 17:29 ` [PATCH RFC v1 06/15] sfc: fix XDP-redirect in this driver Jesper Dangaard Brouer
2020-03-17 17:29 ` [PATCH RFC v1 07/15] sfc: add XDP frame size Jesper Dangaard Brouer
2020-03-17 17:29 ` [PATCH RFC v1 08/15] xdp: allow bpf_xdp_adjust_tail() to grow packet size Jesper Dangaard Brouer
2020-03-17 17:29 ` [PATCH RFC v1 09/15] xdp: clear grow memory in bpf_xdp_adjust_tail() Jesper Dangaard Brouer
2020-03-17 20:38 ` Jakub Kicinski
2020-03-18 9:15 ` Toke Høiland-Jørgensen
2020-03-18 10:25 ` Jesper Dangaard Brouer
2020-03-19 5:35 ` Alexei Starovoitov
2020-03-17 17:29 ` [PATCH RFC v1 10/15] net: XDP-generic determining XDP frame size Jesper Dangaard Brouer
2020-03-17 17:30 ` [PATCH RFC v1 11/15] xdp: xdp_frame add member frame_sz and handle in convert_to_xdp_frame Jesper Dangaard Brouer
2020-03-17 17:30 ` Jesper Dangaard Brouer [this message]
2020-03-17 17:30 ` [PATCH RFC v1 13/15] tun: add XDP frame size Jesper Dangaard Brouer
2020-03-17 17:30 ` [PATCH RFC v1 14/15] veth: xdp using frame_sz in veth driver Jesper Dangaard Brouer
2020-03-17 17:30 ` [PATCH RFC v1 15/15] dpaa2-eth: add XDP frame size Jesper Dangaard Brouer
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