tx_done is not used for napi_complete_done(). Thus, NAPI busy polling mechanism by gro_flush_timeout and napi_defer_hard_irqs will not able be triggered after a packet is transmitted when there is no receive packet.

Fix this by taking the maximum value between tx_done and rx_done as overall budget completed by the rxtx NAPI poll to ensure XDP Tx ZC operation is continuously polling for next Tx frame. This gives benefit of lower packet submission processing latency and jitter under XDP Tx ZC mode.

Performance of tx-only using xdp-sock on Intel ADL-S platform is the same with and without this patch.

root@intel-corei7-64:~# ./xdpsock -i enp0s30f4 -t -z -q 1 -n 10 sock0@enp0s30f4:1 txonly xdp-drv pps pkts 10.00 rx 0 0 tx 511630 8659520

sock0@enp0s30f4:1 txonly xdp-drv pps pkts 10.00 rx 0 0 tx 511625 13775808

sock0@enp0s30f4:1 txonly xdp-drv pps pkts 10.00 rx 0 0 tx 511619 18892032

Fixes: 132c32ee5bc0 ("net: stmmac: Add TX via XDP zero-copy socket") Cc: stable@vger.kernel.org # 5.13.x Co-developed-by: Ong Boon Leong boon.leong.ong@intel.com Signed-off-by: Ong Boon Leong boon.leong.ong@intel.com Signed-off-by: Song Yoong Siang yoong.siang.song@intel.com --- drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c index ed0cd3920171..97238359e101 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c @@ -5347,7 +5347,7 @@ static int stmmac_napi_poll_rxtx(struct napi_struct *napi, int budget) struct stmmac_channel *ch = container_of(napi, struct stmmac_channel, rxtx_napi); struct stmmac_priv *priv = ch->priv_data; - int rx_done, tx_done; + int rx_done, tx_done, rxtx_done; u32 chan = ch->index;

priv->xstats.napi_poll++; @@ -5357,14 +5357,16 @@ static int stmmac_napi_poll_rxtx(struct napi_struct *napi, int budget)

rx_done = stmmac_rx_zc(priv, budget, chan);

+ rxtx_done = max(tx_done, rx_done); + /* If either TX or RX work is not complete, return budget * and keep pooling */ - if (tx_done >= budget || rx_done >= budget) + if (rxtx_done >= budget) return budget;

/* all work done, exit the polling mode */ - if (napi_complete_done(napi, rx_done)) { + if (napi_complete_done(napi, rxtx_done)) { unsigned long flags;

spin_lock_irqsave(&ch->lock, flags); @@ -5375,7 +5377,7 @@ static int stmmac_napi_poll_rxtx(struct napi_struct *napi, int budget) spin_unlock_irqrestore(&ch->lock, flags); }

- return min(rx_done, budget - 1); + return min(rxtx_done, budget - 1); }

/**