diff options
| author | Jesper Dangaard Brouer <brouer@redhat.com> | 2020-05-14 12:49:38 +0200 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2020-05-15 06:21:54 +0200 |
| commit | db612f749e2454c506f20155bba2871f0307d133 (patch) | |
| tree | 6c06de2552a875163ec1c586cc03cd2c104c0c67 /kernel/bpf | |
| parent | xdp: Xdp_frame add member frame_sz and handle in convert_to_xdp_frame (diff) | |
| download | linux-db612f749e2454c506f20155bba2871f0307d133.tar.xz linux-db612f749e2454c506f20155bba2871f0307d133.zip | |
xdp: Cpumap redirect use frame_sz and increase skb_tailroom
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>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/158945337822.97035.13557959180460986059.stgit@firesoul
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/cpumap.c | 21 |
1 files 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); |