+.. SPDX-License-Identifier: GPL-2.0
- HOWTO for multiqueue network device support
- ===========================================
+===========================================
+HOWTO for multiqueue network device support
+===========================================
Section 1: Base driver requirements for implementing multiqueue support
+=======================================================================
Intro: Kernel support for multiqueue devices
---------------------------------------------------------
Kernel support for multiqueue devices is always present.
-Section 1: Base driver requirements for implementing multiqueue support
------------------------------------------------------------------------
-
Base drivers are required to use the new alloc_etherdev_mq() or
alloc_netdev_mq() functions to allocate the subqueues for the device. The
underlying kernel API will take care of the allocation and deallocation of
Section 2: Qdisc support for multiqueue devices
-
------------------------------------------------
+===============================================
Currently two qdiscs are optimized for multiqueue devices. The first is the
default pfifo_fast qdisc. This qdisc supports one qdisc per hardware queue.
Section 3: Brief howto using MULTIQ for multiqueue devices
----------------------------------------------------------------
+==========================================================
The userspace command 'tc,' part of the iproute2 package, is used to configure
qdiscs. To add the MULTIQ qdisc to your network device, assuming the device
-is called eth0, run the following command:
+is called eth0, run the following command::
-# tc qdisc add dev eth0 root handle 1: multiq
+ # tc qdisc add dev eth0 root handle 1: multiq
The qdisc will allocate the number of bands to equal the number of queues that
the device reports, and bring the qdisc online. Assuming eth0 has 4 Tx
-queues, the band mapping would look like:
+queues, the band mapping would look like::
-band 0 => queue 0
-band 1 => queue 1
-band 2 => queue 2
-band 3 => queue 3
+ band 0 => queue 0
+ band 1 => queue 1
+ band 2 => queue 2
+ band 3 => queue 3
Traffic will begin flowing through each queue based on either the simple_tx_hash
function or based on netdev->select_queue() if you have it defined.
The behavior of tc filters remains the same. However a new tc action,
skbedit, has been added. Assuming you wanted to route all traffic to a
specific host, for example 192.168.0.3, through a specific queue you could use
-this action and establish a filter such as:
+this action and establish a filter such as::
-tc filter add dev eth0 parent 1: protocol ip prio 1 u32 \
- match ip dst 192.168.0.3 \
- action skbedit queue_mapping 3
+ tc filter add dev eth0 parent 1: protocol ip prio 1 u32 \
+ match ip dst 192.168.0.3 \
+ action skbedit queue_mapping 3
-Author: Alexander Duyck <alexander.h.duyck@intel.com>
-Original Author: Peter P. Waskiewicz Jr. <peter.p.waskiewicz.jr@intel.com>
+:Author: Alexander Duyck <alexander.h.duyck@intel.com>
+:Original Author: Peter P. Waskiewicz Jr. <peter.p.waskiewicz.jr@intel.com>