diff options
| author |   Eric Dumazet <edumazet@google.com> | 2025-04-08 20:27:42 +0000 |
|---|---|---|
| committer |   Jakub Kicinski <kuba@kernel.org> | 2025-04-09 18:03:31 -0700 |
| commit | 229671ac60e298b85c2644f52d7e487e9f487d06 (patch) | |
| tree | de47fc6ce5c2747e5774443dc8860e66d5c829b1 | |
| parent | octeontx2-pf: Add error log forcn10k_map_unmap_rq_policer() (diff) | |
| download | wireguard-linux-229671ac60e298b85c2644f52d7e487e9f487d06.tar.xz wireguard-linux-229671ac60e298b85c2644f52d7e487e9f487d06.zip | |
net: remove cpu stall in txq_trans_update()
txq_trans_update() currently uses txq->xmit_lock_owner
to conditionally update txq->trans_start.
For regular devices, txq->xmit_lock_owner is updated
from HARD_TX_LOCK() and HARD_TX_UNLOCK(), and this apparently
causes cpu stalls.
Using dev->lltx, which sits in a read-mostly cache-line,
and already used in HARD_TX_LOCK() and HARD_TX_UNLOCK()
helps cpu prediction.
On an AMD EPYC 7B12 dual socket server, tcp_rr with 128 threads
and 30,000 flows gets a 5 % increase in throughput.
As explained in commit 95ecba62e2fd ("net: fix races in
netdev_tx_sent_queue()/dev_watchdog()") I am planning
to no longer update txq->trans_start in the fast path
in a followup patch.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250408202742.2145516-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | drivers/net/ethernet/ti/am65-cpsw-nuss.c | 2 | ||||
| -rw-r--r-- | include/linux/netdevice.h | 7 |
2 files changed, 5 insertions, 4 deletions
diff --git a/drivers/net/ethernet/ti/am65-cpsw-nuss.c b/drivers/net/ethernet/ti/am65-cpsw-nuss.c index c9fd34787c99..e78de79a5d78 100644 --- a/drivers/net/ethernet/ti/am65-cpsw-nuss.c +++ b/drivers/net/ethernet/ti/am65-cpsw-nuss.c @@ -427,7 +427,7 @@ static void am65_cpsw_nuss_ndo_host_tx_timeout(struct net_device *ndev, if (netif_tx_queue_stopped(netif_txq)) { /* try recover if stopped by us */ - txq_trans_update(netif_txq); + txq_trans_update(ndev, netif_txq); netif_tx_wake_queue(netif_txq); } } diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index dece2ae396a1..a28a08046615 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -4693,9 +4693,10 @@ static inline void __netif_tx_unlock_bh(struct netdev_queue *txq) /* * txq->trans_start can be read locklessly from dev_watchdog() */ -static inline void txq_trans_update(struct netdev_queue *txq) +static inline void txq_trans_update(const struct net_device *dev, + struct netdev_queue *txq) { - if (txq->xmit_lock_owner != -1) + if (!dev->lltx) WRITE_ONCE(txq->trans_start, jiffies); } @@ -5214,7 +5215,7 @@ static inline netdev_tx_t netdev_start_xmit(struct sk_buff *skb, struct net_devi rc = __netdev_start_xmit(ops, skb, dev, more); if (rc == NETDEV_TX_OK) - txq_trans_update(txq); + txq_trans_update(dev, txq); return rc; } |