net: Add max rate tx queue attribute

This adds a tx_maxrate attribute to the tx queue sysfs entry allowing
for max-rate limiting. Along with DCB-ETS and BQL this provides another
knob to tune queue performance. The limit units are Mbps.

By default it is disabled. To disable the rate limitation after it
has been set for a queue, it should be set to zero.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 55 insertions, 12 deletions

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index cf30620a88e1..7e58bd7ec232 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -951,6 +951,60 @@ static ssize_t show_trans_timeout(struct netdev_queue *queue,
         return sprintf(buf, "%lu", trans_timeout);
 }
 
+#ifdef CONFIG_XPS
+static inline unsigned int get_netdev_queue_index(struct netdev_queue *queue)
+{
+        struct net_device *dev = queue->dev;
+        int i;
+
+        for (i = 0; i < dev->num_tx_queues; i++)
+                if (queue == &dev->_tx[i])
+                        break;
+
+        BUG_ON(i >= dev->num_tx_queues);
+
+        return i;
+}
+
+static ssize_t show_tx_maxrate(struct netdev_queue *queue,
+                               struct netdev_queue_attribute *attribute,
+                               char *buf)
+{
+        return sprintf(buf, "%lu\n", queue->tx_maxrate);
+}
+
+static ssize_t set_tx_maxrate(struct netdev_queue *queue,
+                              struct netdev_queue_attribute *attribute,
+                              const char *buf, size_t len)
+{
+        struct net_device *dev = queue->dev;
+        int err, index = get_netdev_queue_index(queue);
+        u32 rate = 0;
+
+        err = kstrtou32(buf, 10, &rate);
+        if (err < 0)
+                return err;
+
+        if (!rtnl_trylock())
+                return restart_syscall();
+
+        err = -EOPNOTSUPP;
+        if (dev->netdev_ops->ndo_set_tx_maxrate)
+                err = dev->netdev_ops->ndo_set_tx_maxrate(dev, index, rate);
+
+        rtnl_unlock();
+        if (!err) {
+                queue->tx_maxrate = rate;
+                return len;
+        }
+        return err;
+}
+
+static struct netdev_queue_attribute queue_tx_maxrate =
+        __ATTR(tx_maxrate, S_IRUGO | S_IWUSR,
+               show_tx_maxrate, set_tx_maxrate);
+#endif
+
 static struct netdev_queue_attribute queue_trans_timeout =
         __ATTR(tx_timeout, S_IRUGO, show_trans_timeout, NULL);
 
@@ -1065,18 +1119,6 @@ static struct attribute_group dql_group = {
 #endif /* CONFIG_BQL */
 
 #ifdef CONFIG_XPS
-static unsigned int get_netdev_queue_index(struct netdev_queue *queue)
-{
-        struct net_device *dev = queue->dev;
-        unsigned int i;
-
-        i = queue - dev->_tx;
-        BUG_ON(i >= dev->num_tx_queues);
-
-        return i;
-}
-
-
 static ssize_t show_xps_map(struct netdev_queue *queue,
                             struct netdev_queue_attribute *attribute, char *buf)
 {
@@ -1153,6 +1195,7 @@ static struct attribute *netdev_queue_default_attrs[] = {
         &queue_trans_timeout.attr,
 #ifdef CONFIG_XPS
         &xps_cpus_attribute.attr,
+        &queue_tx_maxrate.attr,
 #endif
         NULL
 };