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Message-ID: <20231018010758.2382742-1-kuba@kernel.org>
Date: Tue, 17 Oct 2023 18:07:58 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org,
edumazet@...gle.com,
pabeni@...hat.com,
Jakub Kicinski <kuba@...nel.org>,
ecree.xilinx@...il.com,
corbet@....net,
linux-doc@...r.kernel.org
Subject: [PATCH net-next] docs: networking: document multi-RSS context
There seems to be no docs for the concept of multiple RSS
contexts and how to configure it. I had to explain it three
times recently, the last one being the charm, document it.
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
CC: ecree.xilinx@...il.com
CC: corbet@....net
CC: linux-doc@...r.kernel.org
---
Documentation/networking/scaling.rst | 42 ++++++++++++++++++++++++++++
1 file changed, 42 insertions(+)
diff --git a/Documentation/networking/scaling.rst b/Documentation/networking/scaling.rst
index 92c9fb46d6a2..03ae19a689fc 100644
--- a/Documentation/networking/scaling.rst
+++ b/Documentation/networking/scaling.rst
@@ -105,6 +105,48 @@ a separate CPU. For interrupt handling, HT has shown no benefit in
initial tests, so limit the number of queues to the number of CPU cores
in the system.
+Dedicated RSS contexts
+~~~~~~~~~~~~~~~~~~~~~~
+
+Modern NICs support creating multiple co-existing RSS configurations
+which are selected based on explicit matching rules. This can be very
+useful when application wants to constrain the set of queues receiving
+traffic for e.g. a particular destination port or IP address.
+The example below shows how to direct all traffic to TCP port 22
+to queues 0 and 1.
+
+To create an additional RSS context use::
+
+ # ethtool -X eth0 hfunc toeplitz context new
+ New RSS context is 1
+
+Kernel reports back the ID of the allocated context (the default, always
+present RSS context has ID of 0). The new context can be queried and
+modified using the same APIs as the default context::
+
+ # ethtool -x eth0 context 1
+ RX flow hash indirection table for eth0 with 13 RX ring(s):
+ 0: 0 1 2 3 4 5 6 7
+ 8: 8 9 10 11 12 0 1 2
+ [...]
+ # ethtool -X eth0 equal 2 context 1
+ # ethtool -x eth0 context 1
+ RX flow hash indirection table for eth0 with 13 RX ring(s):
+ 0: 0 1 0 1 0 1 0 1
+ 8: 0 1 0 1 0 1 0 1
+ [...]
+
+To make use of the new context direct traffic to it using an n-tuple
+filter::
+
+ # ethtool -N eth0 flow-type tcp6 dst-port 22 context 1
+ Added rule with ID 1023
+
+When done, remove the context and the rule::
+
+ # ethtool -N eth0 delete 1023
+ # ethtool -X eth0 context 1 delete
+
RPS: Receive Packet Steering
============================
--
2.41.0
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