[openwrt/openwrt] bcm4908: optimize Ethernet driver by using build_skb()
LEDE Commits
lede-commits at lists.infradead.org
Thu Oct 27 10:02:51 PDT 2022
rmilecki pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/6a02205a4d94a7b6a888ec55d1aecd60ebb20d77
commit 6a02205a4d94a7b6a888ec55d1aecd60ebb20d77
Author: Rafał Miłecki <rafal at milecki.pl>
AuthorDate: Thu Oct 27 18:57:39 2022 +0200
bcm4908: optimize Ethernet driver by using build_skb()
This should slightly improve performance thanks to the better cache
usage.
Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
---
...1-net-broadcom-bcm4908_enet-use-build_skb.patch | 152 +++++++++++++++++++++
1 file changed, 152 insertions(+)
diff --git a/target/linux/bcm4908/patches-5.10/079-v6.2-0001-net-broadcom-bcm4908_enet-use-build_skb.patch b/target/linux/bcm4908/patches-5.10/079-v6.2-0001-net-broadcom-bcm4908_enet-use-build_skb.patch
new file mode 100644
index 0000000000..1a3dc62d44
--- /dev/null
+++ b/target/linux/bcm4908/patches-5.10/079-v6.2-0001-net-broadcom-bcm4908_enet-use-build_skb.patch
@@ -0,0 +1,152 @@
+From 3a1cc23a75abcd9cea585eb84846507363d58397 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal at milecki.pl>
+Date: Tue, 25 Oct 2022 15:22:45 +0200
+Subject: [PATCH] net: broadcom: bcm4908_enet: use build_skb()
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+RX code can be more efficient with the build_skb(). Allocating actual
+SKB around eth packet buffer - right before passing it up - results in
+a better cache usage.
+
+Without RPS (echo 0 > rps_cpus) BCM4908 NAT masq performance "jumps"
+between two speeds: ~900 Mbps and 940 Mbps (it's a 4 CPUs SoC). This
+change bumps the lower speed from 905 Mb/s to 918 Mb/s (tested using
+single stream iperf 2.0.5 traffic).
+
+There are more optimizations to consider. One obvious to try is GRO
+however as BCM4908 doesn't do hw csum is may actually lower performance.
+Sometimes. Some early testing:
+
+┌─────────────────────────────────┬─────────────────────┬────────────────────┐
+│ │ netif_receive_skb() │ napi_gro_receive() │
+├─────────────────────────────────┼─────────────────────┼────────────────────┤
+│ netdev_alloc_skb() │ 905 Mb/s │ 892 Mb/s │
+│ napi_alloc_frag() + build_skb() │ 918 Mb/s │ 917 Mb/s │
+└─────────────────────────────────┴─────────────────────┴────────────────────┘
+
+Another ideas:
+1. napi_build_skb()
+2. skb_copy_from_linear_data() for small packets
+
+Those need proper testing first though. That can be done later.
+
+Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
+Link: https://lore.kernel.org/r/20221025132245.22871-1-zajec5@gmail.com
+Signed-off-by: Paolo Abeni <pabeni at redhat.com>
+---
+ drivers/net/ethernet/broadcom/bcm4908_enet.c | 53 +++++++++++++-------
+ 1 file changed, 36 insertions(+), 17 deletions(-)
+
+--- a/drivers/net/ethernet/broadcom/bcm4908_enet.c
++++ b/drivers/net/ethernet/broadcom/bcm4908_enet.c
+@@ -36,13 +36,24 @@
+ #define ENET_MAX_ETH_OVERHEAD (ETH_HLEN + BRCM_MAX_TAG_LEN + VLAN_HLEN + \
+ ETH_FCS_LEN + 4) /* 32 */
+
++#define ENET_RX_SKB_BUF_SIZE (NET_SKB_PAD + NET_IP_ALIGN + \
++ ETH_HLEN + BRCM_MAX_TAG_LEN + VLAN_HLEN + \
++ ENET_MTU_MAX + ETH_FCS_LEN + 4)
++#define ENET_RX_SKB_BUF_ALLOC_SIZE (SKB_DATA_ALIGN(ENET_RX_SKB_BUF_SIZE) + \
++ SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
++#define ENET_RX_BUF_DMA_OFFSET (NET_SKB_PAD + NET_IP_ALIGN)
++#define ENET_RX_BUF_DMA_SIZE (ENET_RX_SKB_BUF_SIZE - ENET_RX_BUF_DMA_OFFSET)
++
+ struct bcm4908_enet_dma_ring_bd {
+ __le32 ctl;
+ __le32 addr;
+ } __packed;
+
+ struct bcm4908_enet_dma_ring_slot {
+- struct sk_buff *skb;
++ union {
++ void *buf; /* RX */
++ struct sk_buff *skb; /* TX */
++ };
+ unsigned int len;
+ dma_addr_t dma_addr;
+ };
+@@ -259,22 +270,21 @@ static int bcm4908_enet_dma_alloc_rx_buf
+ u32 tmp;
+ int err;
+
+- slot->len = ENET_MTU_MAX + ENET_MAX_ETH_OVERHEAD;
+-
+- slot->skb = netdev_alloc_skb(enet->netdev, slot->len);
+- if (!slot->skb)
++ slot->buf = napi_alloc_frag(ENET_RX_SKB_BUF_ALLOC_SIZE);
++ if (!slot->buf)
+ return -ENOMEM;
+
+- slot->dma_addr = dma_map_single(dev, slot->skb->data, slot->len, DMA_FROM_DEVICE);
++ slot->dma_addr = dma_map_single(dev, slot->buf + ENET_RX_BUF_DMA_OFFSET,
++ ENET_RX_BUF_DMA_SIZE, DMA_FROM_DEVICE);
+ err = dma_mapping_error(dev, slot->dma_addr);
+ if (err) {
+ dev_err(dev, "Failed to map DMA buffer: %d\n", err);
+- kfree_skb(slot->skb);
+- slot->skb = NULL;
++ skb_free_frag(slot->buf);
++ slot->buf = NULL;
+ return err;
+ }
+
+- tmp = slot->len << DMA_CTL_LEN_DESC_BUFLENGTH_SHIFT;
++ tmp = ENET_RX_BUF_DMA_SIZE << DMA_CTL_LEN_DESC_BUFLENGTH_SHIFT;
+ tmp |= DMA_CTL_STATUS_OWN;
+ if (idx == enet->rx_ring.length - 1)
+ tmp |= DMA_CTL_STATUS_WRAP;
+@@ -314,11 +324,11 @@ static void bcm4908_enet_dma_uninit(stru
+
+ for (i = rx_ring->length - 1; i >= 0; i--) {
+ slot = &rx_ring->slots[i];
+- if (!slot->skb)
++ if (!slot->buf)
+ continue;
+ dma_unmap_single(dev, slot->dma_addr, slot->len, DMA_FROM_DEVICE);
+- kfree_skb(slot->skb);
+- slot->skb = NULL;
++ skb_free_frag(slot->buf);
++ slot->buf = NULL;
+ }
+ }
+
+@@ -576,6 +586,7 @@ static int bcm4908_enet_poll_rx(struct n
+ while (handled < weight) {
+ struct bcm4908_enet_dma_ring_bd *buf_desc;
+ struct bcm4908_enet_dma_ring_slot slot;
++ struct sk_buff *skb;
+ u32 ctl;
+ int len;
+ int err;
+@@ -599,16 +610,24 @@ static int bcm4908_enet_poll_rx(struct n
+
+ if (len < ETH_ZLEN ||
+ (ctl & (DMA_CTL_STATUS_SOP | DMA_CTL_STATUS_EOP)) != (DMA_CTL_STATUS_SOP | DMA_CTL_STATUS_EOP)) {
+- kfree_skb(slot.skb);
++ skb_free_frag(slot.buf);
+ enet->netdev->stats.rx_dropped++;
+ break;
+ }
+
+- dma_unmap_single(dev, slot.dma_addr, slot.len, DMA_FROM_DEVICE);
++ dma_unmap_single(dev, slot.dma_addr, ENET_RX_BUF_DMA_SIZE, DMA_FROM_DEVICE);
++
++ skb = build_skb(slot.buf, ENET_RX_SKB_BUF_ALLOC_SIZE);
++ if (unlikely(!skb)) {
++ skb_free_frag(slot.buf);
++ enet->netdev->stats.rx_dropped++;
++ break;
++ }
++ skb_reserve(skb, ENET_RX_BUF_DMA_OFFSET);
++ skb_put(skb, len - ETH_FCS_LEN);
++ skb->protocol = eth_type_trans(skb, enet->netdev);
+
+- skb_put(slot.skb, len - ETH_FCS_LEN);
+- slot.skb->protocol = eth_type_trans(slot.skb, enet->netdev);
+- netif_receive_skb(slot.skb);
++ netif_receive_skb(skb);
+
+ enet->netdev->stats.rx_packets++;
+ enet->netdev->stats.rx_bytes += len;
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