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Message-ID: <AB07E875-FFAE-4F5F-8A8C-EA38CE9D4580@gmail.com>
Date: Wed, 31 Jul 2019 11:26:39 -0700
From: "Jonathan Lemon" <jonathan.lemon@...il.com>
To: "Kevin Laatz" <kevin.laatz@...el.com>
Cc: netdev@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
bjorn.topel@...el.com, magnus.karlsson@...el.com,
jakub.kicinski@...ronome.com, saeedm@...lanox.com,
maximmi@...lanox.com, stephen@...workplumber.org,
bruce.richardson@...el.com, ciara.loftus@...el.com,
bpf@...r.kernel.org, intel-wired-lan@...ts.osuosl.org
Subject: Re: [PATCH bpf-next v4 09/11] samples/bpf: add buffer recycling for
unaligned chunks to xdpsock
On 30 Jul 2019, at 1:53, Kevin Laatz wrote:
> This patch adds buffer recycling support for unaligned buffers. Since
> we
> don't mask the addr to 2k at umem_reg in unaligned mode, we need to
> make
> sure we give back the correct (original) addr to the fill queue. We
> achieve
> this using the new descriptor format and associated masks. The new
> format
> uses the upper 16-bits for the offset and the lower 48-bits for the
> addr.
> Since we have a field for the offset, we no longer need to modify the
> actual address. As such, all we have to do to get back the original
> address
> is mask for the lower 48 bits (i.e. strip the offset and we get the
> address
> on it's own).
>
> Signed-off-by: Kevin Laatz <kevin.laatz@...el.com>
> Signed-off-by: Bruce Richardson <bruce.richardson@...el.com>
>
> ---
> v2:
> - Removed unused defines
> - Fix buffer recycling for unaligned case
> - Remove --buf-size (--frame-size merged before this)
> - Modifications to use the new descriptor format for buffer
> recycling
> ---
> samples/bpf/xdpsock_user.c | 24 +++++++++++++++---------
> 1 file changed, 15 insertions(+), 9 deletions(-)
>
> diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
> index 756b00eb1afe..62b2059cd0e3 100644
> --- a/samples/bpf/xdpsock_user.c
> +++ b/samples/bpf/xdpsock_user.c
> @@ -475,6 +475,7 @@ static void kick_tx(struct xsk_socket_info *xsk)
>
> static inline void complete_tx_l2fwd(struct xsk_socket_info *xsk)
> {
> + struct xsk_umem_info *umem = xsk->umem;
> u32 idx_cq = 0, idx_fq = 0;
> unsigned int rcvd;
> size_t ndescs;
> @@ -487,22 +488,21 @@ static inline void complete_tx_l2fwd(struct
> xsk_socket_info *xsk)
> xsk->outstanding_tx;
>
> /* re-add completed Tx buffers */
> - rcvd = xsk_ring_cons__peek(&xsk->umem->cq, ndescs, &idx_cq);
> + rcvd = xsk_ring_cons__peek(&umem->cq, ndescs, &idx_cq);
> if (rcvd > 0) {
> unsigned int i;
> int ret;
>
> - ret = xsk_ring_prod__reserve(&xsk->umem->fq, rcvd, &idx_fq);
> + ret = xsk_ring_prod__reserve(&umem->fq, rcvd, &idx_fq);
> while (ret != rcvd) {
> if (ret < 0)
> exit_with_error(-ret);
> - ret = xsk_ring_prod__reserve(&xsk->umem->fq, rcvd,
> - &idx_fq);
> + ret = xsk_ring_prod__reserve(&umem->fq, rcvd, &idx_fq);
> }
> +
> for (i = 0; i < rcvd; i++)
> - *xsk_ring_prod__fill_addr(&xsk->umem->fq, idx_fq++) =
> - *xsk_ring_cons__comp_addr(&xsk->umem->cq,
> - idx_cq++);
> + *xsk_ring_prod__fill_addr(&umem->fq, idx_fq++) =
> + *xsk_ring_cons__comp_addr(&umem->cq, idx_cq++);
>
> xsk_ring_prod__submit(&xsk->umem->fq, rcvd);
> xsk_ring_cons__release(&xsk->umem->cq, rcvd);
> @@ -549,7 +549,11 @@ static void rx_drop(struct xsk_socket_info *xsk)
> for (i = 0; i < rcvd; i++) {
> u64 addr = xsk_ring_cons__rx_desc(&xsk->rx, idx_rx)->addr;
> u32 len = xsk_ring_cons__rx_desc(&xsk->rx, idx_rx++)->len;
> - char *pkt = xsk_umem__get_data(xsk->umem->buffer, addr);
> + u64 offset = addr >> XSK_UNALIGNED_BUF_OFFSET_SHIFT;
> +
> + addr &= XSK_UNALIGNED_BUF_ADDR_MASK;
> + char *pkt = xsk_umem__get_data(xsk->umem->buffer,
> + addr + offset);
The mask constants should not be part of the api - this should be
hidden behind an accessor.
Something like:
u64 addr = xsk_umem__get_addr(xsk->umem, handle);
> hex_dump(pkt, len, addr);
> *xsk_ring_prod__fill_addr(&xsk->umem->fq, idx_fq++) = addr;
> @@ -655,7 +659,9 @@ static void l2fwd(struct xsk_socket_info *xsk)
> idx_rx)->addr;
> u32 len = xsk_ring_cons__rx_desc(&xsk->rx,
> idx_rx++)->len;
> - char *pkt = xsk_umem__get_data(xsk->umem->buffer, addr);
> + u64 offset = addr >> XSK_UNALIGNED_BUF_OFFSET_SHIFT;
> + char *pkt = xsk_umem__get_data(xsk->umem->buffer,
> + (addr & XSK_UNALIGNED_BUF_ADDR_MASK) + offset);
>
> swap_mac_addresses(pkt);
>
> --
> 2.17.1
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