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authorLinus Torvalds <torvalds@linux-foundation.org>2008-10-11 12:33:18 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-10-11 12:33:18 -0400
commit4dd9ec4946b4651a295d3bc8df9c15ac692a8f4e (patch)
treeafb300c752de7175bb2df4722d5c857e070c75d9 /Documentation/networking/multiqueue.txt
parent86ed5a93b8b56e4e0877b914af0e10883a196384 (diff)
parent6861ff35ec5b60fafaf8651754c9a75142bfa9a4 (diff)
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6: (1075 commits) myri10ge: update driver version number to 1.4.3-1.369 r8169: add shutdown handler r8169: preliminary 8168d support r8169: support additional 8168cp chipset r8169: change default behavior for mildly identified 8168c chipsets r8169: add a new 8168cp flavor r8169: add a new 8168c flavor (bis) r8169: add a new 8168c flavor r8169: sync existing 8168 device hardware start sequences with vendor driver r8169: 8168b Tx performance tweak r8169: make room for more specific 8168 hardware start procedure r8169: shuffle some registers handling around (8168 operation only) r8169: new phy init parameters for the 8168b r8169: update phy init parameters r8169: wake up the PHY of the 8168 af_key: fix SADB_X_SPDDELETE response ath9k: Fix return code when ath9k_hw_setpower() fails on reset ath9k: remove nasty FAIL macro from ath9k_hw_reset() gre: minor cleanups in netlink interface gre: fix copy and paste error ...
Diffstat (limited to 'Documentation/networking/multiqueue.txt')
-rw-r--r--Documentation/networking/multiqueue.txt54
1 files changed, 53 insertions, 1 deletions
diff --git a/Documentation/networking/multiqueue.txt b/Documentation/networking/multiqueue.txt
index d391ea631141..4caa0e314cc2 100644
--- a/Documentation/networking/multiqueue.txt
+++ b/Documentation/networking/multiqueue.txt
@@ -24,4 +24,56 @@ netif_{start|stop|wake}_subqueue() functions to manage each queue while the
24device is still operational. netdev->queue_lock is still used when the device 24device is still operational. netdev->queue_lock is still used when the device
25comes online or when it's completely shut down (unregister_netdev(), etc.). 25comes online or when it's completely shut down (unregister_netdev(), etc.).
26 26
27Author: Peter P. Waskiewicz Jr. <peter.p.waskiewicz.jr@intel.com> 27
28Section 2: Qdisc support for multiqueue devices
29
30-----------------------------------------------
31
32Currently two qdiscs are optimized for multiqueue devices. The first is the
33default pfifo_fast qdisc. This qdisc supports one qdisc per hardware queue.
34A new round-robin qdisc, sch_multiq also supports multiple hardware queues. The
35qdisc is responsible for classifying the skb's and then directing the skb's to
36bands and queues based on the value in skb->queue_mapping. Use this field in
37the base driver to determine which queue to send the skb to.
38
39sch_multiq has been added for hardware that wishes to avoid head-of-line
40blocking. It will cycle though the bands and verify that the hardware queue
41associated with the band is not stopped prior to dequeuing a packet.
42
43On qdisc load, the number of bands is based on the number of queues on the
44hardware. Once the association is made, any skb with skb->queue_mapping set,
45will be queued to the band associated with the hardware queue.
46
47
48Section 3: Brief howto using MULTIQ for multiqueue devices
49---------------------------------------------------------------
50
51The userspace command 'tc,' part of the iproute2 package, is used to configure
52qdiscs. To add the MULTIQ qdisc to your network device, assuming the device
53is called eth0, run the following command:
54
55# tc qdisc add dev eth0 root handle 1: multiq
56
57The qdisc will allocate the number of bands to equal the number of queues that
58the device reports, and bring the qdisc online. Assuming eth0 has 4 Tx
59queues, the band mapping would look like:
60
61band 0 => queue 0
62band 1 => queue 1
63band 2 => queue 2
64band 3 => queue 3
65
66Traffic will begin flowing through each queue based on either the simple_tx_hash
67function or based on netdev->select_queue() if you have it defined.
68
69The behavior of tc filters remains the same. However a new tc action,
70skbedit, has been added. Assuming you wanted to route all traffic to a
71specific host, for example 192.168.0.3, through a specific queue you could use
72this action and establish a filter such as:
73
74tc filter add dev eth0 parent 1: protocol ip prio 1 u32 \
75 match ip dst 192.168.0.3 \
76 action skbedit queue_mapping 3
77
78Author: Alexander Duyck <alexander.h.duyck@intel.com>
79Original Author: Peter P. Waskiewicz Jr. <peter.p.waskiewicz.jr@intel.com>