netdev:bfin_mac: reclaim and free tx skb as soon as possible after transfer
SKBs hold onto resources that can't be held indefinitely, such as TCP
socket references and netfilter conntrack state. So if a packet is left
in TX ring for a long time, there might be a TCP socket that cannot be
closed and freed up.
Current blackfin EMAC driver always reclaim and free used tx skbs in future
transfers. The problem is that future transfer may not come as soon as
possible. This patch start a timer after transfer to reclaim and free skb.
There is nearly no performance drop with this patch.
TX interrupt is not enabled because of a strange behavior of the Blackfin EMAC.
If EMAC TX transfer control is turned on, endless TX interrupts are triggered
no matter if TX DMA is enabled or not. Since DMA walks down the ring automatically,
TX transfer control can't be turned off in the middle. The only way is to disable
TX interrupt completely.
Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/bfin_mac.c b/drivers/net/bfin_mac.c
index 368f333..012613f 100644
--- a/drivers/net/bfin_mac.c
+++ b/drivers/net/bfin_mac.c
@@ -922,61 +922,73 @@
# define bfin_tx_hwtstamp(dev, skb)
#endif
-static void adjust_tx_list(void)
+static inline void _tx_reclaim_skb(void)
{
- int timeout_cnt = MAX_TIMEOUT_CNT;
-
- if (tx_list_head->status.status_word != 0 &&
- current_tx_ptr != tx_list_head) {
- goto adjust_head; /* released something, just return; */
- }
-
- /*
- * if nothing released, check wait condition
- * current's next can not be the head,
- * otherwise the dma will not stop as we want
- */
- if (current_tx_ptr->next->next == tx_list_head) {
- while (tx_list_head->status.status_word == 0) {
- udelay(10);
- if (tx_list_head->status.status_word != 0 ||
- !(bfin_read_DMA2_IRQ_STATUS() & DMA_RUN)) {
- goto adjust_head;
- }
- if (timeout_cnt-- < 0) {
- printk(KERN_ERR DRV_NAME
- ": wait for adjust tx list head timeout\n");
- break;
- }
- }
- if (tx_list_head->status.status_word != 0) {
- goto adjust_head;
- }
- }
-
- return;
-
-adjust_head:
do {
tx_list_head->desc_a.config &= ~DMAEN;
tx_list_head->status.status_word = 0;
if (tx_list_head->skb) {
dev_kfree_skb(tx_list_head->skb);
tx_list_head->skb = NULL;
- } else {
- printk(KERN_ERR DRV_NAME
- ": no sk_buff in a transmitted frame!\n");
}
tx_list_head = tx_list_head->next;
- } while (tx_list_head->status.status_word != 0 &&
- current_tx_ptr != tx_list_head);
- return;
+ } while (tx_list_head->status.status_word != 0);
+}
+
+static void tx_reclaim_skb(struct bfin_mac_local *lp)
+{
+ int timeout_cnt = MAX_TIMEOUT_CNT;
+
+ if (tx_list_head->status.status_word != 0)
+ _tx_reclaim_skb();
+
+ if (current_tx_ptr->next == tx_list_head) {
+ while (tx_list_head->status.status_word == 0) {
+ /* slow down polling to avoid too many queue stop. */
+ udelay(10);
+ /* reclaim skb if DMA is not running. */
+ if (!(bfin_read_DMA2_IRQ_STATUS() & DMA_RUN))
+ break;
+ if (timeout_cnt-- < 0)
+ break;
+ }
+
+ if (timeout_cnt >= 0)
+ _tx_reclaim_skb();
+ else
+ netif_stop_queue(lp->ndev);
+ }
+
+ if (current_tx_ptr->next != tx_list_head &&
+ netif_queue_stopped(lp->ndev))
+ netif_wake_queue(lp->ndev);
+
+ if (tx_list_head != current_tx_ptr) {
+ /* shorten the timer interval if tx queue is stopped */
+ if (netif_queue_stopped(lp->ndev))
+ lp->tx_reclaim_timer.expires =
+ jiffies + (TX_RECLAIM_JIFFIES >> 4);
+ else
+ lp->tx_reclaim_timer.expires =
+ jiffies + TX_RECLAIM_JIFFIES;
+
+ mod_timer(&lp->tx_reclaim_timer,
+ lp->tx_reclaim_timer.expires);
+ }
+
+ return;
+}
+
+static void tx_reclaim_skb_timeout(unsigned long lp)
+{
+ tx_reclaim_skb((struct bfin_mac_local *)lp);
}
static int bfin_mac_hard_start_xmit(struct sk_buff *skb,
struct net_device *dev)
{
+ struct bfin_mac_local *lp = netdev_priv(dev);
u16 *data;
u32 data_align = (unsigned long)(skb->data) & 0x3;
union skb_shared_tx *shtx = skb_tx(skb);
@@ -1009,8 +1021,6 @@
skb->len);
current_tx_ptr->desc_a.start_addr =
(u32)current_tx_ptr->packet;
- if (current_tx_ptr->status.status_word != 0)
- current_tx_ptr->status.status_word = 0;
blackfin_dcache_flush_range(
(u32)current_tx_ptr->packet,
(u32)(current_tx_ptr->packet + skb->len + 2));
@@ -1022,6 +1032,9 @@
*/
SSYNC();
+ /* always clear status buffer before start tx dma */
+ current_tx_ptr->status.status_word = 0;
+
/* enable this packet's dma */
current_tx_ptr->desc_a.config |= DMAEN;
@@ -1037,13 +1050,14 @@
bfin_write_EMAC_OPMODE(bfin_read_EMAC_OPMODE() | TE);
out:
- adjust_tx_list();
-
bfin_tx_hwtstamp(dev, skb);
current_tx_ptr = current_tx_ptr->next;
dev->stats.tx_packets++;
dev->stats.tx_bytes += (skb->len);
+
+ tx_reclaim_skb(lp);
+
return NETDEV_TX_OK;
}
@@ -1167,8 +1181,11 @@
#ifdef CONFIG_NET_POLL_CONTROLLER
static void bfin_mac_poll(struct net_device *dev)
{
+ struct bfin_mac_local *lp = netdev_priv(dev);
+
disable_irq(IRQ_MAC_RX);
bfin_mac_interrupt(IRQ_MAC_RX, dev);
+ tx_reclaim_skb(lp);
enable_irq(IRQ_MAC_RX);
}
#endif /* CONFIG_NET_POLL_CONTROLLER */
@@ -1232,12 +1249,27 @@
/* Our watchdog timed out. Called by the networking layer */
static void bfin_mac_timeout(struct net_device *dev)
{
+ struct bfin_mac_local *lp = netdev_priv(dev);
+
pr_debug("%s: %s\n", dev->name, __func__);
bfin_mac_disable();
- /* reset tx queue */
- tx_list_tail = tx_list_head->next;
+ del_timer(&lp->tx_reclaim_timer);
+
+ /* reset tx queue and free skb */
+ while (tx_list_head != current_tx_ptr) {
+ tx_list_head->desc_a.config &= ~DMAEN;
+ tx_list_head->status.status_word = 0;
+ if (tx_list_head->skb) {
+ dev_kfree_skb(tx_list_head->skb);
+ tx_list_head->skb = NULL;
+ }
+ tx_list_head = tx_list_head->next;
+ }
+
+ if (netif_queue_stopped(lp->ndev))
+ netif_wake_queue(lp->ndev);
bfin_mac_enable();
@@ -1430,6 +1462,7 @@
SET_NETDEV_DEV(ndev, &pdev->dev);
platform_set_drvdata(pdev, ndev);
lp = netdev_priv(ndev);
+ lp->ndev = ndev;
/* Grab the MAC address in the MAC */
*(__le32 *) (&(ndev->dev_addr[0])) = cpu_to_le32(bfin_read_EMAC_ADDRLO());
@@ -1485,6 +1518,10 @@
ndev->netdev_ops = &bfin_mac_netdev_ops;
ndev->ethtool_ops = &bfin_mac_ethtool_ops;
+ init_timer(&lp->tx_reclaim_timer);
+ lp->tx_reclaim_timer.data = (unsigned long)lp;
+ lp->tx_reclaim_timer.function = tx_reclaim_skb_timeout;
+
spin_lock_init(&lp->lock);
/* now, enable interrupts */