From 5d8ce41c6a878afac157a61299a9f810bf80995e Mon Sep 17 00:00:00 2001 From: Julian Wiedmann Date: Wed, 18 Mar 2020 13:54:50 +0100 Subject: s390/qeth: balance the TX queue selection for IQD devices For ucast traffic, qeth_iqd_select_queue() falls back to netdev_pick_tx(). This will potentially use skb_tx_hash() to distribute the flow over all active TX queues - so txq 0 is a valid selection, and qeth_iqd_select_queue() needs to check for this and put it on some other queue. As a result, the distribution for ucast flows is unbalanced and hits QETH_IQD_MIN_UCAST_TXQ heavier than the other queues. Open-coding a custom variant of skb_tx_hash() isn't an option, since netdev_pick_tx() also gives us eg. access to XPS. But we can pull a little trick: add a single TC class that excludes the mcast txq, and thus encourage skb_tx_hash() to not pick the mcast txq. Signed-off-by: Julian Wiedmann Signed-off-by: David S. Miller --- drivers/s390/net/qeth_core.h | 1 + drivers/s390/net/qeth_core_main.c | 45 ++++++++++++++++++++++++++++++++++++++- drivers/s390/net/qeth_ethtool.c | 2 +- 3 files changed, 46 insertions(+), 2 deletions(-) (limited to 'drivers/s390') diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h index 94cd39631eee..b8b356aca674 100644 --- a/drivers/s390/net/qeth_core.h +++ b/drivers/s390/net/qeth_core.h @@ -1061,6 +1061,7 @@ netdev_features_t qeth_features_check(struct sk_buff *skb, struct net_device *dev, netdev_features_t features); void qeth_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats); +int qeth_set_real_num_tx_queues(struct qeth_card *card, unsigned int count); u16 qeth_iqd_select_queue(struct net_device *dev, struct sk_buff *skb, u8 cast_type, struct net_device *sb_dev); int qeth_open(struct net_device *dev); diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c index aa493edc0082..e1d984c29e1f 100644 --- a/drivers/s390/net/qeth_core_main.c +++ b/drivers/s390/net/qeth_core_main.c @@ -6025,7 +6025,7 @@ int qeth_setup_netdev(struct qeth_card *card) num_tx_queues = dev->real_num_tx_queues; } - return netif_set_real_num_tx_queues(dev, num_tx_queues); + return qeth_set_real_num_tx_queues(card, num_tx_queues); } EXPORT_SYMBOL_GPL(qeth_setup_netdev); @@ -6641,6 +6641,47 @@ void qeth_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats) } EXPORT_SYMBOL_GPL(qeth_get_stats64); +#define TC_IQD_UCAST 0 +static void qeth_iqd_set_prio_tc_map(struct net_device *dev, + unsigned int ucast_txqs) +{ + unsigned int prio; + + /* IQD requires mcast traffic to be placed on a dedicated queue, and + * qeth_iqd_select_queue() deals with this. + * For unicast traffic, we defer the queue selection to the stack. + * By installing a trivial prio map that spans over only the unicast + * queues, we can encourage the stack to spread the ucast traffic evenly + * without selecting the mcast queue. + */ + + /* One traffic class, spanning over all active ucast queues: */ + netdev_set_num_tc(dev, 1); + netdev_set_tc_queue(dev, TC_IQD_UCAST, ucast_txqs, + QETH_IQD_MIN_UCAST_TXQ); + + /* Map all priorities to this traffic class: */ + for (prio = 0; prio <= TC_BITMASK; prio++) + netdev_set_prio_tc_map(dev, prio, TC_IQD_UCAST); +} + +int qeth_set_real_num_tx_queues(struct qeth_card *card, unsigned int count) +{ + struct net_device *dev = card->dev; + int rc; + + /* Per netif_setup_tc(), adjust the mapping first: */ + if (IS_IQD(card)) + qeth_iqd_set_prio_tc_map(dev, count - 1); + + rc = netif_set_real_num_tx_queues(dev, count); + + if (rc && IS_IQD(card)) + qeth_iqd_set_prio_tc_map(dev, dev->real_num_tx_queues - 1); + + return rc; +} + u16 qeth_iqd_select_queue(struct net_device *dev, struct sk_buff *skb, u8 cast_type, struct net_device *sb_dev) { @@ -6648,6 +6689,8 @@ u16 qeth_iqd_select_queue(struct net_device *dev, struct sk_buff *skb, if (cast_type != RTN_UNICAST) return QETH_IQD_MCAST_TXQ; + if (dev->real_num_tx_queues == QETH_IQD_MIN_TXQ) + return QETH_IQD_MIN_UCAST_TXQ; txq = netdev_pick_tx(dev, skb, sb_dev); return (txq == QETH_IQD_MCAST_TXQ) ? QETH_IQD_MIN_UCAST_TXQ : txq; diff --git a/drivers/s390/net/qeth_ethtool.c b/drivers/s390/net/qeth_ethtool.c index 715ee0015847..079b695032ef 100644 --- a/drivers/s390/net/qeth_ethtool.c +++ b/drivers/s390/net/qeth_ethtool.c @@ -201,7 +201,7 @@ static int qeth_set_channels(struct net_device *dev, return -EOPNOTSUPP; } - return netif_set_real_num_tx_queues(dev, channels->tx_count); + return qeth_set_real_num_tx_queues(card, channels->tx_count); } static int qeth_get_tunable(struct net_device *dev, -- cgit v1.2.3