diff options
author | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-07-12 13:31:22 -0700 |
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committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-07-12 13:31:22 -0700 |
commit | e1bd2ac5a6b7a8b625e40c9e9f8b6dea4cf22f85 (patch) | |
tree | 9366e9fb481da2c7195ca3f2bafeffebbf001363 /Documentation/networking/multiqueue.txt | |
parent | 0b9062f6b57a87f22309c6b920a51aaa66ce2a13 (diff) | |
parent | 15028aad00ddf241581fbe74a02ec89cbb28d35d (diff) |
Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
* 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6: (183 commits)
[TG3]: Update version to 3.78.
[TG3]: Add missing NVRAM strapping.
[TG3]: Enable auto MDI.
[TG3]: Fix the polarity bit.
[TG3]: Fix irq_sync race condition.
[NET_SCHED]: ematch: module autoloading
[TCP]: tcp probe wraparound handling and other changes
[RTNETLINK]: rtnl_link: allow specifying initial device address
[RTNETLINK]: rtnl_link API simplification
[VLAN]: Fix MAC address handling
[ETH]: Validate address in eth_mac_addr
[NET]: Fix races in net_rx_action vs netpoll.
[AF_UNIX]: Rewrite garbage collector, fixes race.
[NETFILTER]: {ip, nf}_conntrack_sctp: fix remotely triggerable NULL ptr dereference (CVE-2007-2876)
[NET]: Make all initialized struct seq_operations const.
[UDP]: Fix length check.
[IPV6]: Remove unneeded pointer idev from addrconf_cleanup().
[DECNET]: Another unnecessary net/tcp.h inclusion in net/dn.h
[IPV6]: Make IPV6_{RECV,2292}RTHDR boolean options.
[IPV6]: Do not send RH0 anymore.
...
Fixed up trivial conflict in Documentation/feature-removal-schedule.txt
manually.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/networking/multiqueue.txt')
-rw-r--r-- | Documentation/networking/multiqueue.txt | 111 |
1 files changed, 111 insertions, 0 deletions
diff --git a/Documentation/networking/multiqueue.txt b/Documentation/networking/multiqueue.txt new file mode 100644 index 00000000000..00b60cce222 --- /dev/null +++ b/Documentation/networking/multiqueue.txt @@ -0,0 +1,111 @@ + + HOWTO for multiqueue network device support + =========================================== + +Section 1: Base driver requirements for implementing multiqueue support +Section 2: Qdisc support for multiqueue devices +Section 3: Brief howto using PRIO or RR for multiqueue devices + + +Intro: Kernel support for multiqueue devices +--------------------------------------------------------- + +Kernel support for multiqueue devices is only an API that is presented to the +netdevice layer for base drivers to implement. This feature is part of the +core networking stack, and all network devices will be running on the +multiqueue-aware stack. If a base driver only has one queue, then these +changes are transparent to that driver. + + +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 +the subqueue memory, as well as netdev configuration of where the queues +exist in memory. + +The base driver will also need to manage the queues as it does the global +netdev->queue_lock today. Therefore base drivers should use the +netif_{start|stop|wake}_subqueue() functions to manage each queue while the +device is still operational. netdev->queue_lock is still used when the device +comes online or when it's completely shut down (unregister_netdev(), etc.). + +Finally, the base driver should indicate that it is a multiqueue device. The +feature flag NETIF_F_MULTI_QUEUE should be added to the netdev->features +bitmap on device initialization. Below is an example from e1000: + +#ifdef CONFIG_E1000_MQ + if ( (adapter->hw.mac.type == e1000_82571) || + (adapter->hw.mac.type == e1000_82572) || + (adapter->hw.mac.type == e1000_80003es2lan)) + netdev->features |= NETIF_F_MULTI_QUEUE; +#endif + + +Section 2: Qdisc support for multiqueue devices +----------------------------------------------- + +Currently two qdiscs support multiqueue devices. A new round-robin qdisc, +sch_rr, and sch_prio. The qdisc is responsible for classifying the skb's to +bands and queues, and will store the queue mapping into skb->queue_mapping. +Use this field in the base driver to determine which queue to send the skb +to. + +sch_rr has been added for hardware that doesn't want scheduling policies from +software, so it's a straight round-robin qdisc. It uses the same syntax and +classification priomap that sch_prio uses, so it should be intuitive to +configure for people who've used sch_prio. + +The PRIO qdisc naturally plugs into a multiqueue device. If PRIO has been +built with NET_SCH_PRIO_MQ, then upon load, it will make sure the number of +bands requested is equal to the number of queues on the hardware. If they +are equal, it sets a one-to-one mapping up between the queues and bands. If +they're not equal, it will not load the qdisc. This is the same behavior +for RR. Once the association is made, any skb that is classified will have +skb->queue_mapping set, which will allow the driver to properly queue skb's +to multiple queues. + + +Section 3: Brief howto using PRIO and RR for multiqueue devices +--------------------------------------------------------------- + +The userspace command 'tc,' part of the iproute2 package, is used to configure +qdiscs. To add the PRIO qdisc to your network device, assuming the device is +called eth0, run the following command: + +# tc qdisc add dev eth0 root handle 1: prio bands 4 multiqueue + +This will create 4 bands, 0 being highest priority, and associate those bands +to the queues on your NIC. Assuming eth0 has 4 Tx queues, the band mapping +would look like: + +band 0 => queue 0 +band 1 => queue 1 +band 2 => queue 2 +band 3 => queue 3 + +Traffic will begin flowing through each queue if your TOS values are assigning +traffic across the various bands. For example, ssh traffic will always try to +go out band 0 based on TOS -> Linux priority conversion (realtime traffic), +so it will be sent out queue 0. ICMP traffic (pings) fall into the "normal" +traffic classification, which is band 1. Therefore pings will be send out +queue 1 on the NIC. + +Note the use of the multiqueue keyword. This is only in versions of iproute2 +that support multiqueue networking devices; if this is omitted when loading +a qdisc onto a multiqueue device, the qdisc will load and operate the same +if it were loaded onto a single-queue device (i.e. - sends all traffic to +queue 0). + +Another alternative to multiqueue band allocation can be done by using the +multiqueue option and specify 0 bands. If this is the case, the qdisc will +allocate the number of bands to equal the number of queues that the device +reports, and bring the qdisc online. + +The behavior of tc filters remains the same, where it will override TOS priority +classification. + + +Author: Peter P. Waskiewicz Jr. <peter.p.waskiewicz.jr@intel.com> |