Re: [PATCH bpf-next 04/10] i40e: xsk: terminate NAPI when XSK Rx queue gets full

Maciej Fijalkowski
2022-04-06T17:53:48Z

On Tue, Apr 05, 2022 at 03:04:17PM +0200, Jesper Dangaard Brouer wrote:
>
>
> On 05/04/2022 13.06, Maciej Fijalkowski wrote:
> > Correlate -ENOBUFS that was returned from xdp_do_redirect() with a XSK
> > Rx queue being full. In such case, terminate the softirq processing and
> > let the user space to consume descriptors from XSK Rx queue so that
> > there is room that driver can use later on.
> >
> > Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
> > ---
> > .../ethernet/intel/i40e/i40e_txrx_common.h | 1 +
> > drivers/net/ethernet/intel/i40e/i40e_xsk.c | 21 ++++++++++++-------
> > 2 files changed, 15 insertions(+), 7 deletions(-)
> >
> [...]
>
> I noticed you are only doing this for the Zero-Copy variants.
> Wouldn't this also be a benefit for normal AF_XDP ?

Sorry for the delay, indeed this would improve AF_XDP in copy mode as
well, but only after a fix I have sent (not on lore yet :<).

I'll adjust patches to check for -ENOBUFS in $DRIVER_txrx.c and send a v2.

>
>
> > diff --git a/drivers/net/ethernet/intel/i40e/i40e_xsk.c b/drivers/net/ethernet/intel/i40e/i40e_xsk.c
> > index c1d25b0b0ca2..9f9e4ce9a24d 100644
> > --- a/drivers/net/ethernet/intel/i40e/i40e_xsk.c
> > +++ b/drivers/net/ethernet/intel/i40e/i40e_xsk.c
> > @@ -161,9 +161,10 @@ static int i40e_run_xdp_zc(struct i40e_ring *rx_ring, struct xdp_buff *xdp)
> > if (likely(act == XDP_REDIRECT)) {
> > err = xdp_do_redirect(rx_ring->netdev, xdp, xdp_prog);
> > - if (err)
> > - goto out_failure;
> > - return I40E_XDP_REDIR;
> > + if (!err)
> > + return I40E_XDP_REDIR;
> > + result = (err == -ENOBUFS) ? I40E_XDP_EXIT : I40E_XDP_CONSUMED;
> > + goto out_failure;
> > }
> > switch (act) {
> > @@ -175,6 +176,9 @@ static int i40e_run_xdp_zc(struct i40e_ring *rx_ring, struct xdp_buff *xdp)
> > if (result == I40E_XDP_CONSUMED)
> > goto out_failure;
> > break;
> > + case XDP_DROP:
> > + result = I40E_XDP_CONSUMED;
> > + break;
> > default:
> > bpf_warn_invalid_xdp_action(rx_ring->netdev, xdp_prog, act);
> > fallthrough;
> > @@ -182,9 +186,6 @@ static int i40e_run_xdp_zc(struct i40e_ring *rx_ring, struct xdp_buff *xdp)
> > out_failure:
> > trace_xdp_exception(rx_ring->netdev, xdp_prog, act);
> > fallthrough; /* handle aborts by dropping packet */
> > - case XDP_DROP:
> > - result = I40E_XDP_CONSUMED;
> > - break;
> > }
> > return result;
> > }
> > @@ -370,6 +371,12 @@ int i40e_clean_rx_irq_zc(struct i40e_ring *rx_ring, int budget)
> > xsk_buff_dma_sync_for_cpu(bi, rx_ring->xsk_pool);
> > xdp_res = i40e_run_xdp_zc(rx_ring, bi);
> > + if (xdp_res == I40E_XDP_EXIT) {
> > + failure = true;
> > + xsk_buff_free(bi);
> > + next_to_clean = (next_to_clean + 1) & count_mask;
> > + break;
> > + }
> > i40e_handle_xdp_result_zc(rx_ring, bi, rx_desc, &rx_packets,
> > &rx_bytes, size, xdp_res);
> > total_rx_packets += rx_packets;
> > @@ -382,7 +389,7 @@ int i40e_clean_rx_irq_zc(struct i40e_ring *rx_ring, int budget)
> > cleaned_count = (next_to_clean - rx_ring->next_to_use - 1) & count_mask;
> > if (cleaned_count >= I40E_RX_BUFFER_WRITE)
> > - failure = !i40e_alloc_rx_buffers_zc(rx_ring, cleaned_count);
> > + failure |= !i40e_alloc_rx_buffers_zc(rx_ring, cleaned_count);
> > i40e_finalize_xdp_rx(rx_ring, xdp_xmit);
> > i40e_update_rx_stats(rx_ring, total_rx_bytes, total_rx_packets);
> >
>