From: Jakub Kicinski <kuba@kernel.org>
Date: Tue, 2 Jun 2026 00:37:59 +0000 (-0700)
Subject: eth: bnxt: disable rx-copybreak by default
X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=bd3beb5c8691318048043d6d2c78d78189d66bdd;p=thirdparty%2Flinux.git

eth: bnxt: disable rx-copybreak by default

rx-copybreak requires an extra slab allocation. Since bnxt uses
page pool frags and HDS by default, the rx-copybreak doesn't
buy us anything. The extra pressure on slab causes overload
on pre-sheaves kernels on modern AMD platforms.

In synthetic testing on net-next this patch shows little difference
but I think copybreak is "obvious waste" at this point.

Default rx-copybreak threshold to 0 / disabled.

The "copybreak" defines are really the size bounds for the Rx header
buffer. Rename them.

Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Link: https://patch.msgid.link/20260602003759.1545645-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index d4f93e62f583..3587f39202d2 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -4846,11 +4846,11 @@ static void bnxt_init_ring_params(struct bnxt *bp)
 {
 	unsigned int rx_size;
 
-	bp->rx_copybreak = BNXT_DEFAULT_RX_COPYBREAK;
+	bp->rx_copybreak = 0; /* rx-copybreak disabled by default */
 	/* Try to fit 4 chunks into a 4k page */
 	rx_size = SZ_1K -
 		NET_SKB_PAD - SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
-	bp->dev->cfg->hds_thresh = max(BNXT_DEFAULT_RX_COPYBREAK, rx_size);
+	bp->dev->cfg->hds_thresh = max(BNXT_MIN_RX_HDR_BUF, rx_size);
 }
 
 /* bp->rx_ring_size, bp->tx_ring_size, dev->mtu, BNXT_FLAG_{G|L}RO flags must
@@ -4911,7 +4911,7 @@ void bnxt_set_ring_params(struct bnxt *bp)
 				  ALIGN(max(NET_SKB_PAD, XDP_PACKET_HEADROOM), 8) -
 				  SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
 		} else {
-			rx_size = max3(BNXT_DEFAULT_RX_COPYBREAK,
+			rx_size = max3(BNXT_MIN_RX_HDR_BUF,
 				       bp->rx_copybreak,
 				       bp->dev->cfg_pending->hds_thresh);
 			rx_size = SKB_DATA_ALIGN(rx_size + NET_IP_ALIGN);
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.h b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
index 61c847b36b9f..1920a161841e 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
@@ -36,8 +36,8 @@
 #include <linux/firmware/broadcom/tee_bnxt_fw.h>
 #endif
 
-#define BNXT_DEFAULT_RX_COPYBREAK 256
-#define BNXT_MAX_RX_COPYBREAK 1024
+#define BNXT_MIN_RX_HDR_BUF	256
+#define BNXT_MAX_RX_HDR_BUF	1024
 
 extern struct list_head bnxt_block_cb_list;
 
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
index 9b14134d62d2..edafa79f636c 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ethtool.c
@@ -4594,7 +4594,7 @@ static int bnxt_set_tunable(struct net_device *dev,
 	switch (tuna->id) {
 	case ETHTOOL_RX_COPYBREAK:
 		rx_copybreak = *(u32 *)data;
-		if (rx_copybreak > BNXT_MAX_RX_COPYBREAK)
+		if (rx_copybreak > BNXT_MAX_RX_HDR_BUF)
 			return -ERANGE;
 		if (rx_copybreak != bp->rx_copybreak) {
 			if (netif_running(dev))
@@ -5172,7 +5172,7 @@ static int bnxt_run_loopback(struct bnxt *bp)
 	cpr = &rxr->bnapi->cp_ring;
 	if (bp->flags & BNXT_FLAG_CHIP_P5_PLUS)
 		cpr = rxr->rx_cpr;
-	pkt_size = min(bp->dev->mtu + ETH_HLEN, max(BNXT_DEFAULT_RX_COPYBREAK,
+	pkt_size = min(bp->dev->mtu + ETH_HLEN, max(BNXT_MIN_RX_HDR_BUF,
 						    bp->rx_copybreak));
 	skb = netdev_alloc_skb(bp->dev, pkt_size);
 	if (!skb)