On Thu, 22 Aug 2019 20:12:37 +0300
Ilya Maximets <i.maxim...@samsung.com> wrote:
> Tx code doesn't clear the descriptors' status after cleaning.
> So, if the budget is larger than number of used elems in a ring, some
> descriptors will be accounted twice and xsk_umem_complete_tx will move
> prod_tail far beyond the prod_head breaking the completion queue ring.
>
> Fix that by limiting the number of descriptors to clean by the number
> of used descriptors in the tx ring.
>
> 'ixgbe_clean_xdp_tx_irq()' function refactored to look more like
> 'ixgbe_xsk_clean_tx_ring()' since we're allowed to directly use
> 'next_to_clean' and 'next_to_use' indexes.
>
> Fixes: 8221c5eba8c1 ("ixgbe: add AF_XDP zero-copy Tx support")
> Signed-off-by: Ilya Maximets <i.maxim...@samsung.com>
> ---
>
> Version 3:
> * Reverted some refactoring made for v2.
> * Eliminated 'budget' for tx clean.
> * prefetch returned.
>
> Version 2:
> * 'ixgbe_clean_xdp_tx_irq()' refactored to look more like
> 'ixgbe_xsk_clean_tx_ring()'.
>
> drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c | 29 ++++++++------------
> 1 file changed, 11 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> index 6b609553329f..a3b6d8c89127 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> @@ -633,19 +633,17 @@ static void ixgbe_clean_xdp_tx_buffer(struct ixgbe_ring
> *tx_ring,
> bool ixgbe_clean_xdp_tx_irq(struct ixgbe_q_vector *q_vector,
> struct ixgbe_ring *tx_ring, int napi_budget)
While you're at it, can you please as well remove the 'napi_budget' argument?
It wasn't used at all even before your patch.
I'm jumping late in, but I was really wondering and hesitated with taking
part in discussion since the v1 of this patch - can you elaborate why simply
clearing the DD bit wasn't sufficient?
Maciej
> {
> + u16 ntc = tx_ring->next_to_clean, ntu = tx_ring->next_to_use;
> unsigned int total_packets = 0, total_bytes = 0;
> - u32 i = tx_ring->next_to_clean, xsk_frames = 0;
> - unsigned int budget = q_vector->tx.work_limit;
> struct xdp_umem *umem = tx_ring->xsk_umem;
> union ixgbe_adv_tx_desc *tx_desc;
> struct ixgbe_tx_buffer *tx_bi;
> - bool xmit_done;
> + u32 xsk_frames = 0;
>
> - tx_bi = &tx_ring->tx_buffer_info[i];
> - tx_desc = IXGBE_TX_DESC(tx_ring, i);
> - i -= tx_ring->count;
> + tx_bi = &tx_ring->tx_buffer_info[ntc];
> + tx_desc = IXGBE_TX_DESC(tx_ring, ntc);
>
> - do {
> + while (ntc != ntu) {
> if (!(tx_desc->wb.status & cpu_to_le32(IXGBE_TXD_STAT_DD)))
> break;
>
> @@ -661,22 +659,18 @@ bool ixgbe_clean_xdp_tx_irq(struct ixgbe_q_vector
> *q_vector,
>
> tx_bi++;
> tx_desc++;
> - i++;
> - if (unlikely(!i)) {
> - i -= tx_ring->count;
> + ntc++;
> + if (unlikely(ntc == tx_ring->count)) {
> + ntc = 0;
> tx_bi = tx_ring->tx_buffer_info;
> tx_desc = IXGBE_TX_DESC(tx_ring, 0);
> }
>
> /* issue prefetch for next Tx descriptor */
> prefetch(tx_desc);
> + }
>
> - /* update budget accounting */
> - budget--;
> - } while (likely(budget));
> -
> - i += tx_ring->count;
> - tx_ring->next_to_clean = i;
> + tx_ring->next_to_clean = ntc;
>
> u64_stats_update_begin(&tx_ring->syncp);
> tx_ring->stats.bytes += total_bytes;
> @@ -688,8 +682,7 @@ bool ixgbe_clean_xdp_tx_irq(struct ixgbe_q_vector
> *q_vector,
> if (xsk_frames)
> xsk_umem_complete_tx(umem, xsk_frames);
>
> - xmit_done = ixgbe_xmit_zc(tx_ring, q_vector->tx.work_limit);
> - return budget > 0 && xmit_done;
> + return ixgbe_xmit_zc(tx_ring, q_vector->tx.work_limit);
> }
>
> int ixgbe_xsk_async_xmit(struct net_device *dev, u32 qid)
