Signed-off-by: Tom Herbert <t...@herbertland.com>
---
Documentation/ABI/testing/sysfs-class-net | 8 ++++++++
Documentation/networking/scaling.txt | 26 ++++++++++++++++++++++++++
2 files changed, 34 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-class-net
b/Documentation/ABI/testing/sysfs-class-net
index 668604f..0d2a6a9 100644
--- a/Documentation/ABI/testing/sysfs-class-net
+++ b/Documentation/ABI/testing/sysfs-class-net
@@ -251,3 +251,11 @@ Contact: netdev@vger.kernel.org
Description:
Indicates the unique physical switch identifier of a switch this
port belongs to, as a string.
+
+What: /sys/class/net/<iface>/xps_dev_flow_table_cnt
+Date: October 2016
+KernelVersion: 4.8
+Contact: netdev@vger.kernel.org
+Description:
+ Indicates the number of entries in the XPS socketless flow
+ table.
diff --git a/Documentation/networking/scaling.txt
b/Documentation/networking/scaling.txt
index 59f4db2..7f9590c 100644
--- a/Documentation/networking/scaling.txt
+++ b/Documentation/networking/scaling.txt
@@ -400,6 +400,26 @@ transport layer is responsible for setting ooo_okay
appropriately. TCP,
for instance, sets the flag when all data for a connection has been
acknowledged.
+XPS: Transmit Socketless Flow Steering
+======================================
+
+Not all flows have an associated socket in which the transmit queue and
+ooo information can be saved. For instance, packets being transmitted over
+OVS for VMs do not have a socket that is visible to the kernel. To allow
+XPS to be effectively used a flow hash table is employed to save queue and
+ooo information for such socketless flows.
+
+The idea is that transmit queues are saved for socketless flows in a
+flow table that is indexed by skbuff hash. The flow table entries have
+two values: the queue_index and the head cnt of packets from the TX
+queue. When a packet is being sent without an associated socket the
+hash table is consulted which returns the queue_index to use. The
+returned queue is compared to the queue that would be selected by XPS.
+If they are are different the XPS queue is selected only if the tail cnt
+in the TX queue advances beyond the recorded head cnt. This checks if
+sending the packet on the new queue could cause ooo packets for the
+flow.
+
==== XPS Configuration
XPS is only available if the kconfig symbol CONFIG_XPS is enabled (on by
@@ -409,6 +429,12 @@ queue is configured using the sysfs file entry:
/sys/class/net/<dev>/queues/tx-<n>/xps_cpus
+Transmit socketless flow steering is enabled by setting the number of
+entries in the XPS flow table. This is configured in the sysfs file
+entry:
+
+/sys/class/net/<dev>/xps_dev_flow_table_cnt
+
== Suggested Configuration
For a network device with a single transmission queue, XPS configuration
--
2.9.3
