netdev - [PATCH net v3 6/6] igb: avoid transmit queue timeout in xdp path

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Date:   Mon, 19 Oct 2020 10:05:53 +0200
From:   sven.auhagen@...eatech.de
To:     anthony.l.nguyen@...el.com, maciej.fijalkowski@...el.com,
        kuba@...nel.org
Cc:     davem@...emloft.net, intel-wired-lan@...ts.osuosl.org,
        netdev@...r.kernel.org, nhorman@...hat.com, sassmann@...hat.com,
        sandeep.penigalapati@...el.com, brouer@...hat.com
Subject: [PATCH net v3 6/6] 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.

Acked-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Signed-off-by: Sven Auhagen <sven.auhagen@...eatech.de>
---
 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 55e708f75187..4a082c06f48d 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -2916,6 +2916,8 @@ 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);
 
@@ -2948,6 +2950,9 @@ 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;
-- 
2.20.1