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Date: Wed, 30 Oct 2013 08:00:00 +0100
From: Rafał Miłecki <zajec5@...il.com>
To: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>
Cc: openwrt-devel@...ts.openwrt.org,
Nathan Hintz <nlhintz@...mail.com>,
Rafał Miłecki <zajec5@...il.com>
Subject: [PATCH] bgmac: pass received packet to the netif instead of copying it
Copying whole packets with skb_copy_from_linear_data_offset is a pretty
bad idea. CPU was spending time in __copy_user_common and network
performance was lower. With the new solution iperf-measured speed
increased from 116Mb/s to 134Mb/s.
Signed-off-by: Rafał Miłecki <zajec5@...il.com>
---
Changes since [RFC TRY#2]:
1) Fixed arguments alignment
2) Dropped code fixing old slot in case of bgmac_dma_rx_skb_for_slot
failure. Thanks to Nathan patch bgmac_dma_rx_skb_for_slot doesn't
change anything in slot in case it failed somewhere.
---
drivers/net/ethernet/broadcom/bgmac.c | 66 +++++++++++++++++++--------------
1 file changed, 39 insertions(+), 27 deletions(-)
diff --git a/drivers/net/ethernet/broadcom/bgmac.c b/drivers/net/ethernet/broadcom/bgmac.c
index 9a3fc89..eeb651d 100644
--- a/drivers/net/ethernet/broadcom/bgmac.c
+++ b/drivers/net/ethernet/broadcom/bgmac.c
@@ -315,7 +315,6 @@ static int bgmac_dma_rx_read(struct bgmac *bgmac, struct bgmac_dma_ring *ring,
struct device *dma_dev = bgmac->core->dma_dev;
struct bgmac_slot_info *slot = &ring->slots[ring->start];
struct sk_buff *skb = slot->skb;
- struct sk_buff *new_skb;
struct bgmac_rx_header *rx;
u16 len, flags;
@@ -328,38 +327,51 @@ static int bgmac_dma_rx_read(struct bgmac *bgmac, struct bgmac_dma_ring *ring,
len = le16_to_cpu(rx->len);
flags = le16_to_cpu(rx->flags);
- /* Check for poison and drop or pass the packet */
- if (len == 0xdead && flags == 0xbeef) {
- bgmac_err(bgmac, "Found poisoned packet at slot %d, DMA issue!\n",
- ring->start);
- } else {
+ do {
+ dma_addr_t old_dma_addr = slot->dma_addr;
+ int err;
+
+ /* Check for poison and drop or pass the packet */
+ if (len == 0xdead && flags == 0xbeef) {
+ bgmac_err(bgmac, "Found poisoned packet at slot %d, DMA issue!\n",
+ ring->start);
+ dma_sync_single_for_device(dma_dev,
+ slot->dma_addr,
+ BGMAC_RX_BUF_SIZE,
+ DMA_FROM_DEVICE);
+ break;
+ }
+
/* Omit CRC. */
len -= ETH_FCS_LEN;
- new_skb = netdev_alloc_skb_ip_align(bgmac->net_dev, len);
- if (new_skb) {
- skb_put(new_skb, len);
- skb_copy_from_linear_data_offset(skb, BGMAC_RX_FRAME_OFFSET,
- new_skb->data,
- len);
- skb_checksum_none_assert(skb);
- new_skb->protocol =
- eth_type_trans(new_skb, bgmac->net_dev);
- netif_receive_skb(new_skb);
- handled++;
- } else {
- bgmac->net_dev->stats.rx_dropped++;
- bgmac_err(bgmac, "Allocation of skb for copying packet failed!\n");
+ /* Prepare new skb as replacement */
+ err = bgmac_dma_rx_skb_for_slot(bgmac, slot);
+ if (err) {
+ /* Poison the old skb */
+ rx->len = cpu_to_le16(0xdead);
+ rx->flags = cpu_to_le16(0xbeef);
+
+ dma_sync_single_for_device(dma_dev,
+ slot->dma_addr,
+ BGMAC_RX_BUF_SIZE,
+ DMA_FROM_DEVICE);
+ break;
}
+ bgmac_dma_rx_setup_desc(bgmac, ring, ring->start);
- /* Poison the old skb */
- rx->len = cpu_to_le16(0xdead);
- rx->flags = cpu_to_le16(0xbeef);
- }
+ /* Unmap old skb, we'll pass it to the netfif */
+ dma_unmap_single(dma_dev, old_dma_addr,
+ BGMAC_RX_BUF_SIZE, DMA_FROM_DEVICE);
+
+ skb_put(skb, BGMAC_RX_FRAME_OFFSET + len);
+ skb_pull(skb, BGMAC_RX_FRAME_OFFSET);
- /* Make it back accessible to the hardware */
- dma_sync_single_for_device(dma_dev, slot->dma_addr,
- BGMAC_RX_BUF_SIZE, DMA_FROM_DEVICE);
+ skb_checksum_none_assert(skb);
+ skb->protocol = eth_type_trans(skb, bgmac->net_dev);
+ netif_receive_skb(skb);
+ handled++;
+ } while (0);
if (++ring->start >= BGMAC_RX_RING_SLOTS)
ring->start = 0;
--
1.7.10.4
--
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