[PATCH net-next] r8152: reduce memory copy for rx

From: Hayes Wang
Date: Wed Dec 03 2014 - 00:15:03 EST

If the data size is more than half of the AGG_BUG_SZ, allocate a new
rx buffer and use skb_clone() to avoid the memory copy.

The original method is that allocate the memory and copy data for each
packet in a rx buffer. The new one is that when the data size for a rx
buffer is more than RX_THRESHOLD_CLONED, allocate a new rx buffer and
use skb_clone for each packet in the rx buffer. According to the
experiment, the new mothod has better performance.

Signed-off-by: Hayes Wang <hayeswang@xxxxxxxxxxx>
---
drivers/net/usb/r8152.c | 110 +++++++++++++++++++++++++++++++++---------------
1 file changed, 77 insertions(+), 33 deletions(-)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 4a9ece0..e44b9fb 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -26,7 +26,7 @@
#include <linux/mdio.h>

/* Version Information */
-#define DRIVER_VERSION "v1.07.0 (2014/10/09)"
+#define DRIVER_VERSION "v1.08.0 (2014/11/27)"
#define DRIVER_AUTHOR "Realtek linux nic maintainers <nic_swsd@xxxxxxxxxxx>"
#define DRIVER_DESC "Realtek RTL8152/RTL8153 Based USB Ethernet Adapters"
#define MODULENAME "r8152"
@@ -447,6 +447,8 @@ enum rtl_register_content {
#define RTL8152_RMS (VLAN_ETH_FRAME_LEN + VLAN_HLEN)
#define RTL8153_RMS RTL8153_MAX_PACKET
#define RTL8152_TX_TIMEOUT (5 * HZ)
+#define AGG_BUF_SZ 16384 /* 16K */
+#define RX_THRESHOLD_CLONED (AGG_BUF_SZ / 2)

/* rtl8152 flags */
enum rtl8152_flags {
@@ -534,8 +536,7 @@ struct rx_agg {
struct list_head list;
struct urb *urb;
struct r8152 *context;
- void *buffer;
- void *head;
+ struct sk_buff *skb;
};

struct tx_agg {
@@ -605,9 +606,8 @@ enum tx_csum_stat {
* The RTL chips use a 64 element hash table based on the Ethernet CRC.
*/
static const int multicast_filter_limit = 32;
-static unsigned int agg_buf_sz = 16384;

-#define RTL_LIMITED_TSO_SIZE (agg_buf_sz - sizeof(struct tx_desc) - \
+#define RTL_LIMITED_TSO_SIZE (AGG_BUF_SZ - sizeof(struct tx_desc) - \
VLAN_ETH_HLEN - VLAN_HLEN)

static
@@ -1210,9 +1210,8 @@ static void free_all_mem(struct r8152 *tp)
usb_free_urb(tp->rx_info[i].urb);
tp->rx_info[i].urb = NULL;

- kfree(tp->rx_info[i].buffer);
- tp->rx_info[i].buffer = NULL;
- tp->rx_info[i].head = NULL;
+ dev_kfree_skb(tp->rx_info[i].skb);
+ tp->rx_info[i].skb = NULL;
}

for (i = 0; i < RTL8152_MAX_TX; i++) {
@@ -1231,6 +1230,31 @@ static void free_all_mem(struct r8152 *tp)
tp->intr_buff = NULL;
}

+static struct sk_buff *rtl_alloc_rx_skb(struct r8152 *tp, gfp_t gfp_mask)
+{
+ struct net_device *netdev = tp->netdev;
+ struct sk_buff *skb;
+
+ skb = __netdev_alloc_skb(netdev, AGG_BUF_SZ, gfp_mask);
+ if (!skb)
+ goto out1;
+
+ if (skb->data != rx_agg_align(skb->data)) {
+ int rl;
+
+ dev_kfree_skb_any(skb);
+ skb = __netdev_alloc_skb(netdev, AGG_BUF_SZ + RX_ALIGN,
+ gfp_mask);
+ if (!skb)
+ goto out1;
+
+ rl = (int)(rx_agg_align(skb->data) - (void *)skb->data);
+ skb_reserve(skb, rl);
+ }
+out1:
+ return skb;
+}
+
static int alloc_all_mem(struct r8152 *tp)
{
struct net_device *netdev = tp->netdev;
@@ -1239,7 +1263,6 @@ static int alloc_all_mem(struct r8152 *tp)
struct usb_host_endpoint *ep_intr = alt->endpoint + 2;
struct urb *urb;
int node, i;
- u8 *buf;

node = netdev->dev.parent ? dev_to_node(netdev->dev.parent) : -1;

@@ -1249,39 +1272,33 @@ static int alloc_all_mem(struct r8152 *tp)
skb_queue_head_init(&tp->tx_queue);

for (i = 0; i < RTL8152_MAX_RX; i++) {
- buf = kmalloc_node(agg_buf_sz, GFP_KERNEL, node);
- if (!buf)
- goto err1;
+ struct sk_buff *skb;

- if (buf != rx_agg_align(buf)) {
- kfree(buf);
- buf = kmalloc_node(agg_buf_sz + RX_ALIGN, GFP_KERNEL,
- node);
- if (!buf)
- goto err1;
- }
+ skb = rtl_alloc_rx_skb(tp, GFP_KERNEL);
+ if (!skb)
+ goto err1;

urb = usb_alloc_urb(0, GFP_KERNEL);
if (!urb) {
- kfree(buf);
+ dev_kfree_skb(skb);
goto err1;
}

INIT_LIST_HEAD(&tp->rx_info[i].list);
tp->rx_info[i].context = tp;
tp->rx_info[i].urb = urb;
- tp->rx_info[i].buffer = buf;
- tp->rx_info[i].head = rx_agg_align(buf);
+ tp->rx_info[i].skb = skb;
}

for (i = 0; i < RTL8152_MAX_TX; i++) {
- buf = kmalloc_node(agg_buf_sz, GFP_KERNEL, node);
+ u8 *buf = kmalloc_node(AGG_BUF_SZ, GFP_KERNEL, node);
+
if (!buf)
goto err1;

if (buf != tx_agg_align(buf)) {
kfree(buf);
- buf = kmalloc_node(agg_buf_sz + TX_ALIGN, GFP_KERNEL,
+ buf = kmalloc_node(AGG_BUF_SZ + TX_ALIGN, GFP_KERNEL,
node);
if (!buf)
goto err1;
@@ -1538,7 +1555,7 @@ static int r8152_tx_agg_fill(struct r8152 *tp, struct tx_agg *agg)
tx_data = agg->head;
agg->skb_num = 0;
agg->skb_len = 0;
- remain = agg_buf_sz;
+ remain = AGG_BUF_SZ;

while (remain >= ETH_ZLEN + sizeof(struct tx_desc)) {
struct tx_desc *tx_desc;
@@ -1587,7 +1604,7 @@ static int r8152_tx_agg_fill(struct r8152 *tp, struct tx_agg *agg)

dev_kfree_skb_any(skb);

- remain = agg_buf_sz - (int)(tx_agg_align(tx_data) - agg->head);
+ remain = AGG_BUF_SZ - (int)(tx_agg_align(tx_data) - agg->head);
}

if (!skb_queue_empty(&skb_head)) {
@@ -1666,6 +1683,8 @@ static void rx_bottom(struct r8152 *tp)

list_for_each_safe(cursor, next, &rx_queue) {
struct rx_desc *rx_desc;
+ struct sk_buff *rx_skb;
+ bool cloned = false;
struct rx_agg *agg;
int len_used = 0;
struct urb *urb;
@@ -1678,10 +1697,21 @@ static void rx_bottom(struct r8152 *tp)
if (urb->actual_length < ETH_ZLEN)
goto submit;

- rx_desc = agg->head;
- rx_data = agg->head;
+ rx_skb = agg->skb;
+ rx_desc = (struct rx_desc *)rx_skb->data;
+ rx_data = rx_skb->data;
len_used += sizeof(struct rx_desc);

+ if (!NET_IP_ALIGN && urb->actual_length > RX_THRESHOLD_CLONED) {
+ struct sk_buff *new_skb;
+
+ new_skb = rtl_alloc_rx_skb(tp, GFP_ATOMIC);
+ if (new_skb) {
+ agg->skb = new_skb;
+ cloned = true;
+ }
+ }
+
while (urb->actual_length > len_used) {
struct net_device *netdev = tp->netdev;
struct net_device_stats *stats = &netdev->stats;
@@ -1699,14 +1729,23 @@ static void rx_bottom(struct r8152 *tp)
pkt_len -= CRC_SIZE;
rx_data += sizeof(struct rx_desc);

- skb = netdev_alloc_skb_ip_align(netdev, pkt_len);
+ if (cloned)
+ skb = skb_clone(rx_skb, GFP_ATOMIC);
+ else
+ skb = netdev_alloc_skb_ip_align(netdev,
+ pkt_len);
if (!skb) {
stats->rx_dropped++;
goto find_next_rx;
}

skb->ip_summed = r8152_rx_csum(tp, rx_desc);
- memcpy(skb->data, rx_data, pkt_len);
+
+ if (cloned)
+ skb_reserve(skb, (int)(rx_data - rx_skb->data));
+ else
+ memcpy(skb->data, rx_data, pkt_len);
+
skb_put(skb, pkt_len);
skb->protocol = eth_type_trans(skb, netdev);
rtl_rx_vlan_tag(rx_desc, skb);
@@ -1717,10 +1756,14 @@ static void rx_bottom(struct r8152 *tp)
find_next_rx:
rx_data = rx_agg_align(rx_data + pkt_len + CRC_SIZE);
rx_desc = (struct rx_desc *)rx_data;
- len_used = (int)(rx_data - (u8 *)agg->head);
+ len_used = (int)(rx_data - rx_skb->data);
len_used += sizeof(struct rx_desc);
}

+ /* free the cloned skb */
+ if (cloned)
+ dev_kfree_skb_any(rx_skb);
+
submit:
r8152_submit_rx(tp, agg, GFP_ATOMIC);
}
@@ -1789,10 +1832,11 @@ static void bottom_half(unsigned long data)
static
int r8152_submit_rx(struct r8152 *tp, struct rx_agg *agg, gfp_t mem_flags)
{
+ struct sk_buff *skb = agg->skb;
int ret;

usb_fill_bulk_urb(agg->urb, tp->udev, usb_rcvbulkpipe(tp->udev, 1),
- agg->head, agg_buf_sz,
+ skb->data, AGG_BUF_SZ,
(usb_complete_t)read_bulk_callback, agg);

ret = usb_submit_urb(agg->urb, mem_flags);
@@ -1951,7 +1995,7 @@ static void set_tx_qlen(struct r8152 *tp)
{
struct net_device *netdev = tp->netdev;

- tp->tx_qlen = agg_buf_sz / (netdev->mtu + VLAN_ETH_HLEN + VLAN_HLEN +
+ tp->tx_qlen = AGG_BUF_SZ / (netdev->mtu + VLAN_ETH_HLEN + VLAN_HLEN +
sizeof(struct tx_desc));
}

--
1.9.3

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