From 92651940ab00dbe64722e908f70d816713d677b7 Mon Sep 17 00:00:00 2001 From: Alexander Duyck Date: Fri, 12 Sep 2008 16:29:34 -0700 Subject: pkt_sched: Add multiqueue scheduler support This patch is intended to add a qdisc to support the new tx multiqueue architecture by providing a band for each hardware queue. By doing this it is possible to support a different qdisc per physical hardware queue. This qdisc uses the skb->queue_mapping to select which band to place the traffic onto. It then uses a round robin w/ a check to see if the subqueue is stopped to determine which band to dequeue the packet from. Signed-off-by: Alexander Duyck Signed-off-by: Jeff Kirsher Signed-off-by: David S. Miller --- Documentation/networking/multiqueue.txt | 47 ++++++++++++++++++++++++++++++++- 1 file changed, 46 insertions(+), 1 deletion(-) (limited to 'Documentation/networking') diff --git a/Documentation/networking/multiqueue.txt b/Documentation/networking/multiqueue.txt index d391ea6..5787ee6 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 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.). -Author: Peter P. Waskiewicz Jr. + +Section 2: Qdisc support for multiqueue devices + +----------------------------------------------- + +Currently two qdiscs support multiqueue devices. The first is the default +pfifo_fast qdisc. This qdisc supports one qdisc per hardware queue. A new +round-robin qdisc, sch_multiq also supports multiple hardware queues. The +qdisc is responsible for classifying the skb's and then directing the skb's to +bands and queues based on the value in skb->queue_mapping. Use this field in +the base driver to determine which queue to send the skb to. + +sch_multiq has been added for hardware that wishes to avoid unnecessary +requeuing. It will cycle though the bands and verify that the hardware queue +associated with the band is not stopped prior to dequeuing a packet. + +On qdisc load, the number of bands is based on the number of queues on the +hardware. Once the association is made, any skb with skb->queue_mapping set, +will be queued to the band associated with the 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: + +# 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: + +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 base device has either +the default simple_tx_hash or a custom netdev->select_queue() defined. + +The behavior of tc filters remains the same. + +Author: Alexander Duyck +Original Author: Peter P. Waskiewicz Jr. -- cgit v1.1