netdev - [net 6/9] igb: avoid transmit queue timeout in xdp path

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Date:   Wed,  9 Dec 2020 17:02:49 -0800
From:   Tony Nguyen <anthony.l.nguyen@...el.com>
To:     davem@...emloft.net, kuba@...nel.org
Cc:     Sven Auhagen <sven.auhagen@...eatech.de>, netdev@...r.kernel.org,
        sassmann@...hat.com, anthony.l.nguyen@...el.com,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Sandeep Penigalapati <sandeep.penigalapati@...el.com>
Subject: [net 6/9] igb: avoid transmit queue timeout in xdp path

From: Sven Auhagen <sven.auhagen@...eatech.de>

Since we share the transmit queue with the network stack,
it is possible that we run into a transmit queue timeout.
This will reset the queue.
This happens under high load when XDP is using the
transmit queue pretty much exclusively.

netdev_start_xmit() sets the trans_start variable of the
transmit queue to jiffies which is later utilized by dev_watchdog(),
so to avoid timeout, let stack know that XDP xmit happened by
bumping the trans_start within XDP Tx routines to jiffies.

Fixes: 9cbc948b5a20 ("igb: add XDP support")
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Signed-off-by: Sven Auhagen <sven.auhagen@...eatech.de>
Tested-by: Sandeep Penigalapati <sandeep.penigalapati@...el.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index af6ace6c0f87..0d343d050973 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -2919,6 +2919,8 @@ static int igb_xdp_xmit_back(struct igb_adapter *adapter, struct xdp_buff *xdp)
 
 	nq = txring_txq(tx_ring);
 	__netif_tx_lock(nq, cpu);
+	/* Avoid transmit queue timeout since we share it with the slow path */
+	nq->trans_start = jiffies;
 	ret = igb_xmit_xdp_ring(adapter, tx_ring, xdpf);
 	__netif_tx_unlock(nq);
 
@@ -2951,6 +2953,9 @@ static int igb_xdp_xmit(struct net_device *dev, int n,
 	nq = txring_txq(tx_ring);
 	__netif_tx_lock(nq, cpu);
 
+	/* Avoid transmit queue timeout since we share it with the slow path */
+	nq->trans_start = jiffies;
+
 	for (i = 0; i < n; i++) {
 		struct xdp_frame *xdpf = frames[i];
 		int err;
-- 
2.26.2