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[PATCH] powerpc/cell spidernet refine locking 

The transmit side of the spider ethernet driver currently
places locks around some very large chunks of code. This
results in a fair amount of lock contention is some cases.
This patch makes the locks much more fine-grained, protecting
only the cirtical sections. One lock is used to protect
three locations: the queue head and tail pointers, and the
queue low-watermark location.

Signed-off-by: Linas Vepstas <linas@austin.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: James K Lewis <jklewis@us.ibm.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
This commit is contained in:
Linas Vepstas 2006-10-10 16:14:29 -05:00 committed by Jeff Garzik
parent 68a8c609b3
commit 9cc7bf7edf
1 changed files with 43 additions and 52 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

95
drivers/net/spider_net.c
View File

@ -646,8 +646,9 @@ static int
spider_net_prepare_tx_descr(struct spider_net_card *card,
struct sk_buff *skb)
{
struct spider_net_descr *descr = card->tx_chain.head;
struct spider_net_descr *descr;
dma_addr_t buf;
unsigned long flags;
int length;
length = skb->len;
@ -666,6 +667,10 @@ spider_net_prepare_tx_descr(struct spider_net_card *card,
return -ENOMEM;
}
spin_lock_irqsave(&card->tx_chain.lock, flags);
descr = card->tx_chain.head;
card->tx_chain.head = descr->next;
descr->buf_addr = buf;
descr->buf_size = length;
descr->next_descr_addr = 0;
@ -674,6 +679,8 @@ spider_net_prepare_tx_descr(struct spider_net_card *card,
descr->dmac_cmd_status =
SPIDER_NET_DESCR_CARDOWNED | SPIDER_NET_DMAC_NOCS;
spin_unlock_irqrestore(&card->tx_chain.lock, flags);
if (skb->protocol == htons(ETH_P_IP))
switch (skb->nh.iph->protocol) {
case IPPROTO_TCP:
@ -691,42 +698,17 @@ spider_net_prepare_tx_descr(struct spider_net_card *card,
return 0;
}
/**
* spider_net_release_tx_descr - processes a used tx descriptor
* @card: card structure
* @descr: descriptor to release
*
* releases a used tx descriptor (unmapping, freeing of skb)
*/
static inline void
spider_net_release_tx_descr(struct spider_net_card *card)
{
struct spider_net_descr *descr = card->tx_chain.tail;
struct sk_buff *skb;
unsigned int len;
card->tx_chain.tail = card->tx_chain.tail->next;
descr->dmac_cmd_status |= SPIDER_NET_DESCR_NOT_IN_USE;
/* unmap the skb */
skb = descr->skb;
if (!skb)
return;
len = skb->len < ETH_ZLEN ? ETH_ZLEN : skb->len;
pci_unmap_single(card->pdev, descr->buf_addr, len,
PCI_DMA_TODEVICE);
dev_kfree_skb(skb);
}
static void
spider_net_set_low_watermark(struct spider_net_card *card)
{
unsigned long flags;
int status;
int cnt=0;
int i;
struct spider_net_descr *descr = card->tx_chain.tail;
/* Measure the length of the queue. */
/* Measure the length of the queue. Measurement does not
* need to be precise -- does not need a lock. */
while (descr != card->tx_chain.head) {
status = descr->dmac_cmd_status & SPIDER_NET_DESCR_NOT_IN_USE;
if (status == SPIDER_NET_DESCR_NOT_IN_USE)
@ -746,11 +728,13 @@ spider_net_set_low_watermark(struct spider_net_card *card)
descr = descr->next;
/* Set the new watermark, clear the old watermark */
spin_lock_irqsave(&card->tx_chain.lock, flags);
descr->dmac_cmd_status |= SPIDER_NET_DESCR_TXDESFLG;
if (card->low_watermark && card->low_watermark != descr)
card->low_watermark->dmac_cmd_status =
card->low_watermark->dmac_cmd_status & ~SPIDER_NET_DESCR_TXDESFLG;
card->low_watermark = descr;
spin_unlock_irqrestore(&card->tx_chain.lock, flags);
}
/**
@ -769,21 +753,31 @@ static int
spider_net_release_tx_chain(struct spider_net_card *card, int brutal)
{
struct spider_net_descr_chain *chain = &card->tx_chain;
struct spider_net_descr *descr;
struct sk_buff *skb;
u32 buf_addr;
unsigned long flags;
int status;
spider_net_read_reg(card, SPIDER_NET_GDTDMACCNTR);
while (chain->tail != chain->head) {
status = spider_net_get_descr_status(chain->tail);
spin_lock_irqsave(&chain->lock, flags);
descr = chain->tail;
status = spider_net_get_descr_status(descr);
switch (status) {
case SPIDER_NET_DESCR_COMPLETE:
card->netdev_stats.tx_packets++;
card->netdev_stats.tx_bytes += chain->tail->skb->len;
card->netdev_stats.tx_bytes += descr->skb->len;
break;
case SPIDER_NET_DESCR_CARDOWNED:
if (!brutal)
if (!brutal) {
spin_unlock_irqrestore(&chain->lock, flags);
return 1;
}
/* fallthrough, if we release the descriptors
* brutally (then we don't care about
* SPIDER_NET_DESCR_CARDOWNED) */
@ -800,12 +794,25 @@ spider_net_release_tx_chain(struct spider_net_card *card, int brutal)
default:
card->netdev_stats.tx_dropped++;
if (!brutal)
if (!brutal) {
spin_unlock_irqrestore(&chain->lock, flags);
return 1;
}
}
spider_net_release_tx_descr(card);
}
chain->tail = descr->next;
descr->dmac_cmd_status |= SPIDER_NET_DESCR_NOT_IN_USE;
skb = descr->skb;
buf_addr = descr->buf_addr;
spin_unlock_irqrestore(&chain->lock, flags);
/* unmap the skb */
if (skb) {
int len = skb->len < ETH_ZLEN ? ETH_ZLEN : skb->len;
pci_unmap_single(card->pdev, buf_addr, len, PCI_DMA_TODEVICE);
dev_kfree_skb(skb);
}
}
return 0;
}
@ -857,27 +864,19 @@ spider_net_xmit(struct sk_buff *skb, struct net_device *netdev)
{
struct spider_net_card *card = netdev_priv(netdev);
struct spider_net_descr_chain *chain = &card->tx_chain;
struct spider_net_descr *descr = chain->head;
unsigned long flags;
spin_lock_irqsave(&chain->lock, flags);
spider_net_release_tx_chain(card, 0);
if ((chain->head->next == chain->tail->prev) ||
(spider_net_get_descr_status(descr) != SPIDER_NET_DESCR_NOT_IN_USE) ||
(spider_net_prepare_tx_descr(card, skb) != 0)) {
card->netdev_stats.tx_dropped++;
spin_unlock_irqrestore(&chain->lock, flags);
netif_stop_queue(netdev);
return NETDEV_TX_BUSY;
}
spider_net_set_low_watermark(card);
spider_net_kick_tx_dma(card);
card->tx_chain.head = card->tx_chain.head->next;
spin_unlock_irqrestore(&chain->lock, flags);
return NETDEV_TX_OK;
}
@ -893,16 +892,11 @@ spider_net_xmit(struct sk_buff *skb, struct net_device *netdev)
static void
spider_net_cleanup_tx_ring(struct spider_net_card *card)
{
unsigned long flags;
spin_lock_irqsave(&card->tx_chain.lock, flags);
if ((spider_net_release_tx_chain(card, 0) != 0) &&
(card->netdev->flags & IFF_UP)) {
spider_net_kick_tx_dma(card);
netif_wake_queue(card->netdev);
}
spin_unlock_irqrestore(&card->tx_chain.lock, flags);
}
/**
@ -1930,10 +1924,7 @@ spider_net_stop(struct net_device *netdev)
spider_net_disable_rxdmac(card);
/* release chains */
if (spin_trylock(&card->tx_chain.lock)) {
spider_net_release_tx_chain(card, 1);
spin_unlock(&card->tx_chain.lock);
}
spider_net_release_tx_chain(card, 1);
spider_net_free_chain(card, &card->tx_chain);
spider_net_free_chain(card, &card->rx_chain);