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>

2 files changed, 17 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-net-queues b/Documentation/ABI/testing/sysfs-class-net-queues
index 5e9aeb91d355..0c0df91b1516 100644
--- a/Documentation/ABI/testing/sysfs-class-net-queues
+++ b/Documentation/ABI/testing/sysfs-class-net-queues
@@ -24,6 +24,14 @@ Description:
                 Indicates the number of transmit timeout events seen by this
                 network interface transmit queue.
 
+What:           /sys/class/<iface>/queues/tx-<queue>/tx_maxrate
+Date:           March 2015
+KernelVersion:  4.1
+Contact:        netdev@vger.kernel.org
+Description:
+                A Mbps max-rate set for the queue, a value of zero means disabled,
+                default is disabled.
+
 What:           /sys/class/<iface>/queues/tx-<queue>/xps_cpus
 Date:           November 2010
 KernelVersion:  2.6.38
diff --git a/Documentation/networking/scaling.txt b/Documentation/networking/scaling.txt
index 99ca40e8e810..cbfac0949635 100644
--- a/Documentation/networking/scaling.txt
+++ b/Documentation/networking/scaling.txt
@@ -421,6 +421,15 @@ best CPUs to share a given queue are probably those that share the cache
 with the CPU that processes transmit completions for that queue
 (transmit interrupts).
 
+Per TX Queue rate limitation:
+=============================
+
+These are rate-limitation mechanisms implemented by HW, where currently
+a max-rate attribute is supported, by setting a Mbps value to
+
+/sys/class/net/<dev>/queues/tx-<n>/tx_maxrate
+
+A value of zero means disabled, and this is the default.
 
 Further Information
 ===================