net: dev_weight: TX/RX orthogonality

Oftenly, introducing side effects on packet processing on the other half
of the stack by adjusting one of TX/RX via sysctl is not desirable.
There are cases of demand for asymmetric, orthogonal configurability.

This holds true especially for nodes where RPS for RFS usage on top is
configured and therefore use the 'old dev_weight'. This is quite a
common base configuration setup nowadays, even with NICs of superior processing
support (e.g. aRFS).

A good example use case are nodes acting as noSQL data bases with a
large number of tiny requests and rather fewer but large packets as responses.
It's affordable to have large budget and rx dev_weights for the
requests. But as a side effect having this large a number on TX
processed in one run can overwhelm drivers.

This patch therefore introduces an independent configurability via sysctl to
userland.

Signed-off-by: Matthias Tafelmeier <matthias.tafelmeier@gmx.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 30 insertions, 1 deletions

diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 2a46e4009f62..eaa72eb0399c 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -222,6 +222,21 @@ static int set_default_qdisc(struct ctl_table *table, int write,
 }
 #endif
 
+static int proc_do_dev_weight(struct ctl_table *table, int write,
+			   void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	int ret;
+
+	ret = proc_dointvec(table, write, buffer, lenp, ppos);
+	if (ret != 0)
+		return ret;
+
+	dev_rx_weight = weight_p * dev_weight_rx_bias;
+	dev_tx_weight = weight_p * dev_weight_tx_bias;
+
+	return ret;
+}
+
 static int proc_do_rss_key(struct ctl_table *table, int write,
 			   void __user *buffer, size_t *lenp, loff_t *ppos)
 {
@@ -273,7 +288,21 @@ static struct ctl_table net_core_table[] = {
 		.data		= &weight_p,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec
+		.proc_handler	= proc_do_dev_weight,
+	},
+	{
+		.procname	= "dev_weight_rx_bias",
+		.data		= &dev_weight_rx_bias,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_do_dev_weight,
+	},
+	{
+		.procname	= "dev_weight_tx_bias",
+		.data		= &dev_weight_tx_bias,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_do_dev_weight,
 	},
 	{
 		.procname	= "netdev_max_backlog",