Re: [PATCH net-next v2 5/6] bcm63xx_enet: convert to build_skb
From: Florian Fainelli <f.fainelli@gmail.com>
Date: 2020-12-29 03:25:09
Also in:
linux-arm-kernel, lkml
On 12/24/2020 6:24 AM, Sieng Piaw Liew wrote:
We can increase the efficiency of rx path by using buffers to receive packets then build SKBs around them just before passing into the network stack. In contrast, preallocating SKBs too early reduces CPU cache efficiency. Check if we're in NAPI context when refilling RX. Normally we're almost always running in NAPI context. Dispatch to napi_alloc_frag directly instead of relying on netdev_alloc_frag which does the same but with the overhead of local_bh_disable/enable. Tested on BCM6328 320 MHz and iperf3 -M 512 to measure packet/sec performance. Included netif_receive_skb_list and NET_IP_ALIGN optimizations. Before: [ ID] Interval Transfer Bandwidth Retr [ 4] 0.00-10.00 sec 49.9 MBytes 41.9 Mbits/sec 197 sender [ 4] 0.00-10.00 sec 49.3 MBytes 41.3 Mbits/sec receiver After: [ ID] Interval Transfer Bandwidth Retr [ 4] 0.00-30.00 sec 171 MBytes 47.8 Mbits/sec 272 sender [ 4] 0.00-30.00 sec 170 MBytes 47.6 Mbits/sec receiver
This looks good, however there are a few nits and suggestions below: [snip]
quoted hunk ↗ jump to hunk
@@ -862,6 +868,24 @@ static void bcm_enet_adjust_link(struct net_device *dev) priv->pause_tx ? "tx" : "off"); } +static void bcm_enet_free_rx_buf_ring(struct device *kdev, struct bcm_enet_priv *priv) +{ + int i; + + for (i = 0; i < priv->rx_ring_size; i++) { + struct bcm_enet_desc *desc; + + if (!priv->rx_buf[i]) + continue; + + desc = &priv->rx_desc_cpu[i]; + dma_unmap_single(kdev, desc->address, priv->rx_buf_size, + DMA_FROM_DEVICE); + skb_free_frag(priv->rx_buf[i]); + } + kfree(priv->rx_buf); +}
This is a good helper to introduced, however I would introduce it as a preliminary patch that way it becomes clear when you are doing the sk_buff to buf substitution in the next patch. [snip]
quoted hunk ↗ jump to hunk
@@ -1640,9 +1641,12 @@ static int bcm_enet_change_mtu(struct net_device *dev, int new_mtu) * align rx buffer size to dma burst len, account FCS since * it's appended */ - priv->rx_skb_size = ALIGN(actual_mtu + ETH_FCS_LEN, + priv->rx_buf_size = ALIGN(actual_mtu + ETH_FCS_LEN, priv->dma_maxburst * 4); + priv->rx_frag_size = SKB_DATA_ALIGN(priv->rx_buf_offset + priv->rx_buf_size) + + SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
The alignment of the second line is a bit off and you should aim for the + operator to be on the preceding line, and have SKB_DATA_ALIGN() start on the opening parenthesis of the preceding line. -- Florian