Date: Sun, 14 Nov 2010 14:35:40 +0100 (CET) From: Stefan Richter Subject: firewire: net: throttle TX queue before running out of tlabels This prevents firewire-net from submitting write requests in fast succession until failure due to all 64 transaction labels were used up for unfinished split transactions. The netif_stop/wake_queue API is used for this purpose. Without this stop/wake mechanism, datagrams were simply lost whenever the tlabel pool was exhausted. Plus, tlabel exhaustion by firewire-net also prevented other unrelated outbound transactions to be initiated. The chosen queue depth was checked by me to hit the maximum possible throughput with an OS X peer whose receive DMA is good enough to never reject requests due to busy inbound request FIFO. Current Linux peers show a mixed picture of -5%...+15% change in bandwidth; their current bottleneck are RCODE_BUSY situations (fewer or more, depending on TX queue depth) due to too small AR buffer in firewire-ohci. Maxim Levitsky tested this change with similar watermarks with a Linux peer and some pending firewire-ohci improvements that address the RCODE_BUSY problem and confirmed that these TX queue limits are good. Note: This removes some netif_wake_queue from reception code paths. They were apparently copy&paste artefacts from a nonsensical netif_wake_queue use in the older eth1394 driver. This belongs only into the transmit path. Signed-off-by: Stefan Richter Tested-by: Maxim Levitsky --- drivers/firewire/net.c | 59 ++++++++++++++++++++++++----------------- 1 file changed, 35 insertions(+), 24 deletions(-) Index: b/drivers/firewire/net.c =================================================================== --- a/drivers/firewire/net.c +++ b/drivers/firewire/net.c @@ -27,8 +27,14 @@ #include #include -#define FWNET_MAX_FRAGMENTS 25 /* arbitrary limit */ -#define FWNET_ISO_PAGE_COUNT (PAGE_SIZE < 16 * 1024 ? 4 : 2) +/* rx limits */ +#define FWNET_MAX_FRAGMENTS 30 /* arbitrary, > TX queue depth */ +#define FWNET_ISO_PAGE_COUNT (PAGE_SIZE < 16*1024 ? 4 : 2) + +/* tx limits */ +#define FWNET_MAX_QUEUED_DATAGRAMS 20 /* < 64 = number of tlabels */ +#define FWNET_MIN_QUEUED_DATAGRAMS 10 /* should keep AT DMA busy enough */ +#define FWNET_TX_QUEUE_LEN FWNET_MAX_QUEUED_DATAGRAMS /* ? */ #define IEEE1394_BROADCAST_CHANNEL 31 #define IEEE1394_ALL_NODES (0xffc0 | 0x003f) @@ -640,8 +646,6 @@ static int fwnet_finish_incoming_packet( net->stats.rx_packets++; net->stats.rx_bytes += skb->len; } - if (netif_queue_stopped(net)) - netif_wake_queue(net); return 0; @@ -650,8 +654,6 @@ static int fwnet_finish_incoming_packet( net->stats.rx_dropped++; dev_kfree_skb_any(skb); - if (netif_queue_stopped(net)) - netif_wake_queue(net); return -ENOENT; } @@ -783,15 +785,10 @@ static int fwnet_incoming_packet(struct * Datagram is not complete, we're done for the * moment. */ - spin_unlock_irqrestore(&dev->lock, flags); - - return 0; + retval = 0; fail: spin_unlock_irqrestore(&dev->lock, flags); - if (netif_queue_stopped(net)) - netif_wake_queue(net); - return retval; } @@ -891,6 +888,13 @@ static void fwnet_free_ptask(struct fwne kmem_cache_free(fwnet_packet_task_cache, ptask); } +/* Caller must hold dev->lock. */ +static void dec_queued_datagrams(struct fwnet_device *dev) +{ + if (--dev->queued_datagrams == FWNET_MIN_QUEUED_DATAGRAMS) + netif_wake_queue(dev->netdev); +} + static int fwnet_send_packet(struct fwnet_packet_task *ptask); static void fwnet_transmit_packet_done(struct fwnet_packet_task *ptask) @@ -907,7 +911,7 @@ static void fwnet_transmit_packet_done(s /* Check whether we or the networking TX soft-IRQ is last user. */ free = (ptask->outstanding_pkts == 0 && ptask->enqueued); if (free) - dev->queued_datagrams--; + dec_queued_datagrams(dev); if (ptask->outstanding_pkts == 0) { dev->netdev->stats.tx_packets++; @@ -978,7 +982,7 @@ static void fwnet_transmit_packet_failed /* Check whether we or the networking TX soft-IRQ is last user. */ free = ptask->enqueued; if (free) - dev->queued_datagrams--; + dec_queued_datagrams(dev); dev->netdev->stats.tx_dropped++; dev->netdev->stats.tx_errors++; @@ -1063,7 +1067,7 @@ static int fwnet_send_packet(struct fwne if (!free) ptask->enqueued = true; else - dev->queued_datagrams--; + dec_queued_datagrams(dev); spin_unlock_irqrestore(&dev->lock, flags); @@ -1082,7 +1086,7 @@ static int fwnet_send_packet(struct fwne if (!free) ptask->enqueued = true; else - dev->queued_datagrams--; + dec_queued_datagrams(dev); spin_unlock_irqrestore(&dev->lock, flags); @@ -1248,6 +1252,15 @@ static netdev_tx_t fwnet_tx(struct sk_bu struct fwnet_peer *peer; unsigned long flags; + spin_lock_irqsave(&dev->lock, flags); + + /* Can this happen? */ + if (netif_queue_stopped(dev->netdev)) { + spin_unlock_irqrestore(&dev->lock, flags); + + return NETDEV_TX_BUSY; + } + ptask = kmem_cache_alloc(fwnet_packet_task_cache, GFP_ATOMIC); if (ptask == NULL) goto fail; @@ -1266,9 +1279,6 @@ static netdev_tx_t fwnet_tx(struct sk_bu proto = hdr_buf.h_proto; dg_size = skb->len; - /* serialize access to peer, including peer->datagram_label */ - spin_lock_irqsave(&dev->lock, flags); - /* * Set the transmission type for the packet. ARP packets and IP * broadcast packets are sent via GASP. @@ -1290,7 +1300,7 @@ static netdev_tx_t fwnet_tx(struct sk_bu peer = fwnet_peer_find_by_guid(dev, be64_to_cpu(guid)); if (!peer || peer->fifo == FWNET_NO_FIFO_ADDR) - goto fail_unlock; + goto fail; generation = peer->generation; dest_node = peer->node_id; @@ -1344,7 +1354,8 @@ static netdev_tx_t fwnet_tx(struct sk_bu max_payload += RFC2374_FRAG_HDR_SIZE; } - dev->queued_datagrams++; + if (++dev->queued_datagrams == FWNET_MAX_QUEUED_DATAGRAMS) + netif_stop_queue(dev->netdev); spin_unlock_irqrestore(&dev->lock, flags); @@ -1355,9 +1366,9 @@ static netdev_tx_t fwnet_tx(struct sk_bu return NETDEV_TX_OK; - fail_unlock: - spin_unlock_irqrestore(&dev->lock, flags); fail: + spin_unlock_irqrestore(&dev->lock, flags); + if (ptask) kmem_cache_free(fwnet_packet_task_cache, ptask); @@ -1403,7 +1414,7 @@ static void fwnet_init_dev(struct net_de net->addr_len = FWNET_ALEN; net->hard_header_len = FWNET_HLEN; net->type = ARPHRD_IEEE1394; - net->tx_queue_len = 10; + net->tx_queue_len = FWNET_TX_QUEUE_LEN; } /* caller must hold fwnet_device_mutex */