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 d4f93e62f583640383a8becace33ef64eb8223e7..3587f39202d2788f6981a7dede4370c9578a4036 100644 (file)
--- 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 61c847b36b9ff3516ef0673529772e6fbdc5134e..1920a161841ea8f2ac39651b370332db36b487c7 100644 (file)
--- 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 9b14134d62d25444acab561e1abc01764be9ee3f..edafa79f636c7205f5a80f52cf492ea4f481e0ff 100644 (file)
--- 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)