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Diffstat (limited to 'Documentation/networking')
-rw-r--r-- | Documentation/networking/multiqueue.txt | 47 |
1 files changed, 46 insertions, 1 deletions
diff --git a/Documentation/networking/multiqueue.txt b/Documentation/networking/multiqueue.txt index d391ea631141..5787ee6eca4f 100644 --- a/Documentation/networking/multiqueue.txt +++ b/Documentation/networking/multiqueue.txt | |||
@@ -24,4 +24,49 @@ netif_{start|stop|wake}_subqueue() functions to manage each queue while the | |||
24 | device is still operational. netdev->queue_lock is still used when the device | 24 | device is still operational. netdev->queue_lock is still used when the device |
25 | comes online or when it's completely shut down (unregister_netdev(), etc.). | 25 | comes online or when it's completely shut down (unregister_netdev(), etc.). |
26 | 26 | ||
27 | Author: Peter P. Waskiewicz Jr. <peter.p.waskiewicz.jr@intel.com> | 27 | |
28 | Section 2: Qdisc support for multiqueue devices | ||
29 | |||
30 | ----------------------------------------------- | ||
31 | |||
32 | Currently two qdiscs support multiqueue devices. The first is the default | ||
33 | pfifo_fast qdisc. This qdisc supports one qdisc per hardware queue. A new | ||
34 | round-robin qdisc, sch_multiq also supports multiple hardware queues. The | ||
35 | qdisc is responsible for classifying the skb's and then directing the skb's to | ||
36 | bands and queues based on the value in skb->queue_mapping. Use this field in | ||
37 | the base driver to determine which queue to send the skb to. | ||
38 | |||
39 | sch_multiq has been added for hardware that wishes to avoid unnecessary | ||
40 | requeuing. It will cycle though the bands and verify that the hardware queue | ||
41 | associated with the band is not stopped prior to dequeuing a packet. | ||
42 | |||
43 | On qdisc load, the number of bands is based on the number of queues on the | ||
44 | hardware. Once the association is made, any skb with skb->queue_mapping set, | ||
45 | will be queued to the band associated with the hardware queue. | ||
46 | |||
47 | |||
48 | Section 3: Brief howto using MULTIQ for multiqueue devices | ||
49 | --------------------------------------------------------------- | ||
50 | |||
51 | The userspace command 'tc,' part of the iproute2 package, is used to configure | ||
52 | qdiscs. To add the MULTIQ qdisc to your network device, assuming the device | ||
53 | is called eth0, run the following command: | ||
54 | |||
55 | # tc qdisc add dev eth0 root handle 1: multiq | ||
56 | |||
57 | The qdisc will allocate the number of bands to equal the number of queues that | ||
58 | the device reports, and bring the qdisc online. Assuming eth0 has 4 Tx | ||
59 | queues, the band mapping would look like: | ||
60 | |||
61 | band 0 => queue 0 | ||
62 | band 1 => queue 1 | ||
63 | band 2 => queue 2 | ||
64 | band 3 => queue 3 | ||
65 | |||
66 | Traffic will begin flowing through each queue if your base device has either | ||
67 | the default simple_tx_hash or a custom netdev->select_queue() defined. | ||
68 | |||
69 | The behavior of tc filters remains the same. | ||
70 | |||
71 | Author: Alexander Duyck <alexander.h.duyck@intel.com> | ||
72 | Original Author: Peter P. Waskiewicz Jr. <peter.p.waskiewicz.jr@intel.com> | ||