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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
Jeff Garzik
parent
68a8c609b3
commit
9cc7bf7edf
@ -646,8 +646,9 @@ static int
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spider_net_prepare_tx_descr(struct spider_net_card *card,
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struct sk_buff *skb)
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{
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struct spider_net_descr *descr = card->tx_chain.head;
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struct spider_net_descr *descr;
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dma_addr_t buf;
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unsigned long flags;
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int length;
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length = skb->len;
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@ -666,6 +667,10 @@ spider_net_prepare_tx_descr(struct spider_net_card *card,
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return -ENOMEM;
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}
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spin_lock_irqsave(&card->tx_chain.lock, flags);
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descr = card->tx_chain.head;
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card->tx_chain.head = descr->next;
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descr->buf_addr = buf;
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descr->buf_size = length;
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descr->next_descr_addr = 0;
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@ -674,6 +679,8 @@ spider_net_prepare_tx_descr(struct spider_net_card *card,
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descr->dmac_cmd_status =
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SPIDER_NET_DESCR_CARDOWNED | SPIDER_NET_DMAC_NOCS;
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spin_unlock_irqrestore(&card->tx_chain.lock, flags);
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if (skb->protocol == htons(ETH_P_IP))
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switch (skb->nh.iph->protocol) {
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case IPPROTO_TCP:
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@ -691,42 +698,17 @@ spider_net_prepare_tx_descr(struct spider_net_card *card,
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return 0;
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}
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/**
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* spider_net_release_tx_descr - processes a used tx descriptor
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* @card: card structure
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* @descr: descriptor to release
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*
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* releases a used tx descriptor (unmapping, freeing of skb)
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*/
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static inline void
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spider_net_release_tx_descr(struct spider_net_card *card)
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{
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struct spider_net_descr *descr = card->tx_chain.tail;
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struct sk_buff *skb;
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unsigned int len;
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card->tx_chain.tail = card->tx_chain.tail->next;
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descr->dmac_cmd_status |= SPIDER_NET_DESCR_NOT_IN_USE;
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/* unmap the skb */
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skb = descr->skb;
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if (!skb)
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return;
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len = skb->len < ETH_ZLEN ? ETH_ZLEN : skb->len;
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pci_unmap_single(card->pdev, descr->buf_addr, len,
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PCI_DMA_TODEVICE);
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dev_kfree_skb(skb);
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}
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static void
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spider_net_set_low_watermark(struct spider_net_card *card)
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{
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unsigned long flags;
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int status;
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int cnt=0;
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int i;
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struct spider_net_descr *descr = card->tx_chain.tail;
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/* Measure the length of the queue. */
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/* Measure the length of the queue. Measurement does not
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* need to be precise -- does not need a lock. */
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while (descr != card->tx_chain.head) {
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status = descr->dmac_cmd_status & SPIDER_NET_DESCR_NOT_IN_USE;
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if (status == SPIDER_NET_DESCR_NOT_IN_USE)
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@ -746,11 +728,13 @@ spider_net_set_low_watermark(struct spider_net_card *card)
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descr = descr->next;
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/* Set the new watermark, clear the old watermark */
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spin_lock_irqsave(&card->tx_chain.lock, flags);
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descr->dmac_cmd_status |= SPIDER_NET_DESCR_TXDESFLG;
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if (card->low_watermark && card->low_watermark != descr)
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card->low_watermark->dmac_cmd_status =
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card->low_watermark->dmac_cmd_status & ~SPIDER_NET_DESCR_TXDESFLG;
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card->low_watermark = descr;
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spin_unlock_irqrestore(&card->tx_chain.lock, flags);
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}
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/**
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@ -769,21 +753,31 @@ static int
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spider_net_release_tx_chain(struct spider_net_card *card, int brutal)
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{
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struct spider_net_descr_chain *chain = &card->tx_chain;
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struct spider_net_descr *descr;
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struct sk_buff *skb;
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u32 buf_addr;
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unsigned long flags;
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int status;
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spider_net_read_reg(card, SPIDER_NET_GDTDMACCNTR);
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while (chain->tail != chain->head) {
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status = spider_net_get_descr_status(chain->tail);
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spin_lock_irqsave(&chain->lock, flags);
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descr = chain->tail;
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status = spider_net_get_descr_status(descr);
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switch (status) {
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case SPIDER_NET_DESCR_COMPLETE:
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card->netdev_stats.tx_packets++;
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card->netdev_stats.tx_bytes += chain->tail->skb->len;
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card->netdev_stats.tx_bytes += descr->skb->len;
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break;
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case SPIDER_NET_DESCR_CARDOWNED:
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if (!brutal)
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if (!brutal) {
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spin_unlock_irqrestore(&chain->lock, flags);
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return 1;
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}
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/* fallthrough, if we release the descriptors
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* brutally (then we don't care about
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* SPIDER_NET_DESCR_CARDOWNED) */
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@ -800,12 +794,25 @@ spider_net_release_tx_chain(struct spider_net_card *card, int brutal)
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default:
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card->netdev_stats.tx_dropped++;
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if (!brutal)
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if (!brutal) {
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spin_unlock_irqrestore(&chain->lock, flags);
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return 1;
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}
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}
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spider_net_release_tx_descr(card);
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}
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chain->tail = descr->next;
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descr->dmac_cmd_status |= SPIDER_NET_DESCR_NOT_IN_USE;
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skb = descr->skb;
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buf_addr = descr->buf_addr;
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spin_unlock_irqrestore(&chain->lock, flags);
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/* unmap the skb */
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if (skb) {
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int len = skb->len < ETH_ZLEN ? ETH_ZLEN : skb->len;
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pci_unmap_single(card->pdev, buf_addr, len, PCI_DMA_TODEVICE);
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dev_kfree_skb(skb);
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}
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}
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return 0;
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}
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@ -857,27 +864,19 @@ spider_net_xmit(struct sk_buff *skb, struct net_device *netdev)
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{
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struct spider_net_card *card = netdev_priv(netdev);
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struct spider_net_descr_chain *chain = &card->tx_chain;
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struct spider_net_descr *descr = chain->head;
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unsigned long flags;
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spin_lock_irqsave(&chain->lock, flags);
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spider_net_release_tx_chain(card, 0);
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if ((chain->head->next == chain->tail->prev) ||
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(spider_net_get_descr_status(descr) != SPIDER_NET_DESCR_NOT_IN_USE) ||
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(spider_net_prepare_tx_descr(card, skb) != 0)) {
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card->netdev_stats.tx_dropped++;
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spin_unlock_irqrestore(&chain->lock, flags);
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netif_stop_queue(netdev);
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return NETDEV_TX_BUSY;
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}
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spider_net_set_low_watermark(card);
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spider_net_kick_tx_dma(card);
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card->tx_chain.head = card->tx_chain.head->next;
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spin_unlock_irqrestore(&chain->lock, flags);
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return NETDEV_TX_OK;
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}
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@ -893,16 +892,11 @@ spider_net_xmit(struct sk_buff *skb, struct net_device *netdev)
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static void
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spider_net_cleanup_tx_ring(struct spider_net_card *card)
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{
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unsigned long flags;
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spin_lock_irqsave(&card->tx_chain.lock, flags);
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if ((spider_net_release_tx_chain(card, 0) != 0) &&
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(card->netdev->flags & IFF_UP)) {
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spider_net_kick_tx_dma(card);
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netif_wake_queue(card->netdev);
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}
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spin_unlock_irqrestore(&card->tx_chain.lock, flags);
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}
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/**
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@ -1930,10 +1924,7 @@ spider_net_stop(struct net_device *netdev)
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spider_net_disable_rxdmac(card);
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/* release chains */
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if (spin_trylock(&card->tx_chain.lock)) {
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spider_net_release_tx_chain(card, 1);
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spin_unlock(&card->tx_chain.lock);
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}
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spider_net_release_tx_chain(card, 1);
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spider_net_free_chain(card, &card->tx_chain);
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spider_net_free_chain(card, &card->rx_chain);
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