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Diffstat (limited to 'Documentation/networking/multiqueue.txt')
-rw-r--r-- | Documentation/networking/multiqueue.txt | 90 |
1 files changed, 1 insertions, 89 deletions
diff --git a/Documentation/networking/multiqueue.txt b/Documentation/networking/multiqueue.txt index ea5a42e8f79..d391ea63114 100644 --- a/Documentation/networking/multiqueue.txt +++ b/Documentation/networking/multiqueue.txt | |||
@@ -3,19 +3,11 @@ | |||
3 | =========================================== | 3 | =========================================== |
4 | 4 | ||
5 | Section 1: Base driver requirements for implementing multiqueue support | 5 | Section 1: Base driver requirements for implementing multiqueue support |
6 | Section 2: Qdisc support for multiqueue devices | ||
7 | Section 3: Brief howto using PRIO or RR for multiqueue devices | ||
8 | |||
9 | 6 | ||
10 | Intro: Kernel support for multiqueue devices | 7 | Intro: Kernel support for multiqueue devices |
11 | --------------------------------------------------------- | 8 | --------------------------------------------------------- |
12 | 9 | ||
13 | Kernel support for multiqueue devices is only an API that is presented to the | 10 | Kernel support for multiqueue devices is always present. |
14 | netdevice layer for base drivers to implement. This feature is part of the | ||
15 | core networking stack, and all network devices will be running on the | ||
16 | multiqueue-aware stack. If a base driver only has one queue, then these | ||
17 | changes are transparent to that driver. | ||
18 | |||
19 | 11 | ||
20 | Section 1: Base driver requirements for implementing multiqueue support | 12 | Section 1: Base driver requirements for implementing multiqueue support |
21 | ----------------------------------------------------------------------- | 13 | ----------------------------------------------------------------------- |
@@ -32,84 +24,4 @@ netif_{start|stop|wake}_subqueue() functions to manage each queue while the | |||
32 | 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 |
33 | 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.). |
34 | 26 | ||
35 | Finally, the base driver should indicate that it is a multiqueue device. The | ||
36 | feature flag NETIF_F_MULTI_QUEUE should be added to the netdev->features | ||
37 | bitmap on device initialization. Below is an example from e1000: | ||
38 | |||
39 | #ifdef CONFIG_E1000_MQ | ||
40 | if ( (adapter->hw.mac.type == e1000_82571) || | ||
41 | (adapter->hw.mac.type == e1000_82572) || | ||
42 | (adapter->hw.mac.type == e1000_80003es2lan)) | ||
43 | netdev->features |= NETIF_F_MULTI_QUEUE; | ||
44 | #endif | ||
45 | |||
46 | |||
47 | Section 2: Qdisc support for multiqueue devices | ||
48 | ----------------------------------------------- | ||
49 | |||
50 | Currently two qdiscs support multiqueue devices. A new round-robin qdisc, | ||
51 | sch_rr, and sch_prio. The qdisc is responsible for classifying the skb's to | ||
52 | bands and queues, and will store the queue mapping into skb->queue_mapping. | ||
53 | Use this field in the base driver to determine which queue to send the skb | ||
54 | to. | ||
55 | |||
56 | sch_rr has been added for hardware that doesn't want scheduling policies from | ||
57 | software, so it's a straight round-robin qdisc. It uses the same syntax and | ||
58 | classification priomap that sch_prio uses, so it should be intuitive to | ||
59 | configure for people who've used sch_prio. | ||
60 | |||
61 | In order to utilitize the multiqueue features of the qdiscs, the network | ||
62 | device layer needs to enable multiple queue support. This can be done by | ||
63 | selecting NETDEVICES_MULTIQUEUE under Drivers. | ||
64 | |||
65 | The PRIO qdisc naturally plugs into a multiqueue device. If | ||
66 | NETDEVICES_MULTIQUEUE is selected, then on qdisc load, the number of | ||
67 | bands requested is compared to the number of queues on the hardware. If they | ||
68 | are equal, it sets a one-to-one mapping up between the queues and bands. If | ||
69 | they're not equal, it will not load the qdisc. This is the same behavior | ||
70 | for RR. Once the association is made, any skb that is classified will have | ||
71 | skb->queue_mapping set, which will allow the driver to properly queue skb's | ||
72 | to multiple queues. | ||
73 | |||
74 | |||
75 | Section 3: Brief howto using PRIO and RR for multiqueue devices | ||
76 | --------------------------------------------------------------- | ||
77 | |||
78 | The userspace command 'tc,' part of the iproute2 package, is used to configure | ||
79 | qdiscs. To add the PRIO qdisc to your network device, assuming the device is | ||
80 | called eth0, run the following command: | ||
81 | |||
82 | # tc qdisc add dev eth0 root handle 1: prio bands 4 multiqueue | ||
83 | |||
84 | This will create 4 bands, 0 being highest priority, and associate those bands | ||
85 | to the queues on your NIC. Assuming eth0 has 4 Tx queues, the band mapping | ||
86 | would look like: | ||
87 | |||
88 | band 0 => queue 0 | ||
89 | band 1 => queue 1 | ||
90 | band 2 => queue 2 | ||
91 | band 3 => queue 3 | ||
92 | |||
93 | Traffic will begin flowing through each queue if your TOS values are assigning | ||
94 | traffic across the various bands. For example, ssh traffic will always try to | ||
95 | go out band 0 based on TOS -> Linux priority conversion (realtime traffic), | ||
96 | so it will be sent out queue 0. ICMP traffic (pings) fall into the "normal" | ||
97 | traffic classification, which is band 1. Therefore pings will be send out | ||
98 | queue 1 on the NIC. | ||
99 | |||
100 | Note the use of the multiqueue keyword. This is only in versions of iproute2 | ||
101 | that support multiqueue networking devices; if this is omitted when loading | ||
102 | a qdisc onto a multiqueue device, the qdisc will load and operate the same | ||
103 | if it were loaded onto a single-queue device (i.e. - sends all traffic to | ||
104 | queue 0). | ||
105 | |||
106 | Another alternative to multiqueue band allocation can be done by using the | ||
107 | multiqueue option and specify 0 bands. If this is the case, the qdisc will | ||
108 | allocate the number of bands to equal the number of queues that the device | ||
109 | reports, and bring the qdisc online. | ||
110 | |||
111 | The behavior of tc filters remains the same, where it will override TOS priority | ||
112 | classification. | ||
113 | |||
114 | |||
115 | Author: Peter P. Waskiewicz Jr. <peter.p.waskiewicz.jr@intel.com> | 27 | Author: Peter P. Waskiewicz Jr. <peter.p.waskiewicz.jr@intel.com> |