[PATCH v4] doc: update Linux core isolation guide

[<pbhagavatula@marvell.com>]

From: Pavan Nikhilesh <pbhagavatula@marvell.com>

Update Linux core isolation guide to include isolation from
timers, RCU processing and IRQs.

Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
Acked-by: Jerin Jacob <jerinj@marvell.com>
---
 v4 Changes:
 - Give names to Links to make them clickable. (Thomas)
 - Fix link formatting.

 v3 Changes:
 - Add additional information links for Cgroups.

 v2 Changes:
 - Add references to the parameters used.
 - Add note about Linux cgroups.

 doc/guides/linux_gsg/enable_func.rst | 32 +++++++++++++++++++++++-----
 1 file changed, 27 insertions(+), 5 deletions(-)

diff --git a/doc/guides/linux_gsg/enable_func.rst b/doc/guides/linux_gsg/enable_func.rst
index b15bfb2f9f..b544d2e50b 100644
--- a/doc/guides/linux_gsg/enable_func.rst
+++ b/doc/guides/linux_gsg/enable_func.rst
@@ -126,16 +126,38 @@ Using Linux Core Isolation to Reduce Context Switches
 -----------------------------------------------------

 While the threads used by a DPDK application are pinned to logical cores on the system,
-it is possible for the Linux scheduler to run other tasks on those cores also.
-To help prevent additional workloads from running on those cores,
-it is possible to use the ``isolcpus`` Linux kernel parameter to isolate them from the general Linux scheduler.
+it is possible for the Linux scheduler to run other tasks on those cores.
+To help prevent additional workloads, timers, rcu processing and IRQs from running on those cores, it is possible to use
+the Linux kernel parameters ``isolcpus``, ``nohz_full``, ``irqaffinity`` to isolate them from the general Linux scheduler tasks.

-For example, if DPDK applications are to run on logical cores 2, 4 and 6,
+For example, if a given CPU has 0-7 cores and DPDK applications are to run on logical cores 2, 4 and 6,
 the following should be added to the kernel parameter list:

 .. code-block:: console

-    isolcpus=2,4,6
+    isolcpus=2,4,6 nohz_full=2,4,6 irqaffinity=0,1,3,5,7
+
+.. Note::
+
+         | More detailed information about the above parameters can be found at:
+         | `NO_HZ <https://www.kernel.org/doc/html/latest/timers/no_hz.html>`_
+         | `IRQs <https://www.kernel.org/doc/html/latest/core-api/irq/>`_
+         | `Kernel parameters <https://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html>`_
+
+
+For more fine grained control over resource management and performance tuning one can look
+into ``Linux cgroups``.
+
+Cpusets using cgroups:
+   `CPUSETS <https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/cpusets.html>`_
+
+Systemd (CPUAffinity):
+   `CPUAffinity <https://www.freedesktop.org/software/systemd/man/systemd.exec.html>`_
+
+Also, see:
+   | `CPUSET man pages <https://man7.org/linux/man-pages/man7/cpuset.7.html>`_
+   | `CPU isolation example <https://www.suse.com/c/cpu-isolation-practical-example-part-5/>`_
+   | `Systemd core isolation <https://www.rcannings.com/systemd-core-isolation/>`_

 .. _High_Precision_Event_Timer:

--
2.25.1