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authorAlexander Duyck <alexander.h.duyck@intel.com>2008-09-13 03:29:34 +0400
committerDavid S. Miller <davem@davemloft.net>2008-09-13 03:29:34 +0400
commit92651940ab00dbe64722e908f70d816713d677b7 (patch)
treeb68fdef99784bfa46b67aabaf70c19b0e5e0a144 /Documentation/networking/multiqueue.txt
parent78d15e82754945ee9821fb491b57faf43abfb9d7 (diff)
downloadlinux-92651940ab00dbe64722e908f70d816713d677b7.tar.xz
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 <alexander.h.duyck@intel.com> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation/networking/multiqueue.txt')
-rw-r--r--Documentation/networking/multiqueue.txt47
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
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. <peter.p.waskiewicz.jr@intel.com>
+
+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 <alexander.h.duyck@intel.com>
+Original Author: Peter P. Waskiewicz Jr. <peter.p.waskiewicz.jr@intel.com>