Re: [PATCH net v2 3/3] octeontx2-pf: Do xdp_do_flush() after redirects.

Paolo Abeni
2023-09-21T17:49:51Z

On Mon, 2023-09-18 at 10:58 -0700, Kui-Feng Lee wrote:
>
> On 9/18/23 08:36, Sebastian Andrzej Siewior wrote:
> > xdp_do_flush() should be invoked before leaving the NAPI poll function
> > if XDP-redirect has been performed.
> >
> > Invoke xdp_do_flush() before leaving NAPI.
> >
> > Cc: Geetha sowjanya <gakula@marvell.com>
> > Cc: Subbaraya Sundeep <sbhatta@marvell.com>
> > Cc: Sunil Goutham <sgoutham@marvell.com>
> > Cc: hariprasad <hkelam@marvell.com>
> > Fixes: 06059a1a9a4a5 ("octeontx2-pf: Add XDP support to netdev PF")
> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> > Acked-by: Geethasowjanya Akula <gakula@marvell.com>
> > ---
> > .../marvell/octeontx2/nic/otx2_txrx.c | 19 +++++++++++++------
> > 1 file changed, 13 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
> > index e77d438489557..53b2a4ef52985 100644
> > --- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
> > +++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
> > @@ -29,7 +29,8 @@
> > static bool otx2_xdp_rcv_pkt_handler(struct otx2_nic *pfvf,
> > struct bpf_prog *prog,
> > struct nix_cqe_rx_s *cqe,
> > - struct otx2_cq_queue *cq);
> > + struct otx2_cq_queue *cq,
> > + bool *need_xdp_flush);
> >
> > static int otx2_nix_cq_op_status(struct otx2_nic *pfvf,
> > struct otx2_cq_queue *cq)
> > @@ -337,7 +338,7 @@ static bool otx2_check_rcv_errors(struct otx2_nic *pfvf,
> > static void otx2_rcv_pkt_handler(struct otx2_nic *pfvf,
> > struct napi_struct *napi,
> > struct otx2_cq_queue *cq,
> > - struct nix_cqe_rx_s *cqe)
> > + struct nix_cqe_rx_s *cqe, bool *need_xdp_flush)
> > {
> > struct nix_rx_parse_s *parse = &cqe->parse;
> > struct nix_rx_sg_s *sg = &cqe->sg;
> > @@ -353,7 +354,7 @@ static void otx2_rcv_pkt_handler(struct otx2_nic *pfvf,
> > }
> >
> > if (pfvf->xdp_prog)
> > - if (otx2_xdp_rcv_pkt_handler(pfvf, pfvf->xdp_prog, cqe, cq))
> > + if (otx2_xdp_rcv_pkt_handler(pfvf, pfvf->xdp_prog, cqe, cq, need_xdp_flush))
> > return;
> >
> > skb = napi_get_frags(napi);
> > @@ -388,6 +389,7 @@ static int otx2_rx_napi_handler(struct otx2_nic *pfvf,
> > struct napi_struct *napi,
> > struct otx2_cq_queue *cq, int budget)
> > {
> > + bool need_xdp_flush = false;
> > struct nix_cqe_rx_s *cqe;
> > int processed_cqe = 0;
> >
> > @@ -409,13 +411,15 @@ static int otx2_rx_napi_handler(struct otx2_nic *pfvf,
> > cq->cq_head++;
> > cq->cq_head &= (cq->cqe_cnt - 1);
> >
> > - otx2_rcv_pkt_handler(pfvf, napi, cq, cqe);
> > + otx2_rcv_pkt_handler(pfvf, napi, cq, cqe, &need_xdp_flush);
> >
> > cqe->hdr.cqe_type = NIX_XQE_TYPE_INVALID;
> > cqe->sg.seg_addr = 0x00;
> > processed_cqe++;
> > cq->pend_cqe--;
> > }
> > + if (need_xdp_flush)
> > + xdp_do_flush();
> >
> > /* Free CQEs to HW */
> > otx2_write64(pfvf, NIX_LF_CQ_OP_DOOR,
> > @@ -1354,7 +1358,8 @@ bool otx2_xdp_sq_append_pkt(struct otx2_nic *pfvf, u64 iova, int len, u16 qidx)
> > static bool otx2_xdp_rcv_pkt_handler(struct otx2_nic *pfvf,
> > struct bpf_prog *prog,
> > struct nix_cqe_rx_s *cqe,
> > - struct otx2_cq_queue *cq)
> > + struct otx2_cq_queue *cq,
> > + bool *need_xdp_flush)
> > {
> > unsigned char *hard_start, *data;
> > int qidx = cq->cq_idx;
> > @@ -1391,8 +1396,10 @@ static bool otx2_xdp_rcv_pkt_handler(struct otx2_nic *pfvf,
> >
> > otx2_dma_unmap_page(pfvf, iova, pfvf->rbsize,
> > DMA_FROM_DEVICE);
> > - if (!err)
> > + if (!err) {
> > + *need_xdp_flush = true;
>
> Is it possible to call xdp_do_flush() at the first place (here)?

AFAICT that would kill much/all of the performance benefits of bulk
redirect.

I think the proposed solution is a better one.

Cheers,

Paolo