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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-kernel@vger.kernel.org (open list) Subject: [PATCH 09/10] net: emac: add Byte Queue Limits (BQL) support Date: Mon, 29 Jun 2026 21:16:33 -0700 Message-ID: <20260630041634.284127-10-rosenp@gmail.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260630041634.284127-1-rosenp@gmail.com> References: <20260630041634.284127-1-rosenp@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add BQL to the TX path to improve tail latency under high throughput: - Call netdev_tx_sent_queue() before ringing the TX doorbell - Call netdev_tx_completed_queue() with byte/packet counts after TX completions - Call netdev_reset_queue() on close and full TX reset Assisted-by: opencode:big-pickle Signed-off-by: Rosen Penev --- drivers/net/ethernet/ibm/emac/core.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/net/ethernet/ibm/emac/core.c b/drivers/net/ethernet/ibm/emac/core.c index dba3cdfea340..da5f3d436aa3 100644 --- a/drivers/net/ethernet/ibm/emac/core.c +++ b/drivers/net/ethernet/ibm/emac/core.c @@ -751,6 +751,7 @@ static void emac_full_tx_reset(struct emac_instance *dev) mal_disable_tx_channel(dev->mal, dev->mal_tx_chan); emac_clean_tx_ring(dev); dev->tx_cnt = dev->tx_slot = dev->ack_slot = 0; + netdev_reset_queue(dev->ndev); emac_configure(dev); @@ -1428,6 +1429,7 @@ static int emac_close(struct net_device *ndev) emac_clean_tx_ring(dev); emac_clean_rx_ring(dev); + netdev_reset_queue(ndev); netif_carrier_off(ndev); return 0; @@ -1448,6 +1450,9 @@ static inline netdev_tx_t emac_xmit_finish(struct emac_instance *dev, int len) { struct emac_regs __iomem *p = dev->emacp; struct net_device *ndev = dev->ndev; + struct netdev_queue *txq = netdev_get_tx_queue(ndev, 0); + + netdev_tx_sent_queue(txq, len); /* Send the packet out. If the if makes a significant perf * difference, then we can store the TMR0 value in "dev" @@ -1666,6 +1671,7 @@ static void emac_parse_tx_error(struct emac_instance *dev, u16 ctrl) static void emac_poll_tx(void *param) { struct emac_instance *dev = param; + struct netdev_queue *txq = netdev_get_tx_queue(dev->ndev, 0); u32 bad_mask; DBG2(dev, "poll_tx, %d %d" NL, dev->tx_cnt, dev->ack_slot); @@ -1679,6 +1685,7 @@ static void emac_poll_tx(void *param) if (dev->tx_cnt) { u16 ctrl; int slot = dev->ack_slot, n = 0; + unsigned int bytes = 0; again: ctrl = dev->tx_desc[slot].ctrl; if (!(ctrl & MAL_TX_CTRL_READY)) { @@ -1686,6 +1693,7 @@ static void emac_poll_tx(void *param) ++n; if (skb) { + bytes += skb->len; dev_kfree_skb(skb); dev->tx_skb[slot] = NULL; } @@ -1699,6 +1707,7 @@ static void emac_poll_tx(void *param) } if (n) { dev->ack_slot = slot; + netdev_tx_completed_queue(txq, n, bytes); if (netif_queue_stopped(dev->ndev) && dev->tx_cnt < EMAC_TX_WAKEUP_THRESH) netif_wake_queue(dev->ndev); -- 2.54.0