[PATCH v3] doc: update Linux core isolation guide

[Jerin Jacob]

On Wed, May 18, 2022 at 1:30 AM <pbhagavatula at marvell.com> wrote:
>
> From: Pavan Nikhilesh <pbhagavatula at marvell.com>
>
> Update Linux core isolation guide to include isolation from
> timers, rcu processing and IRQs.

rcu-> RCU

>
> Signed-off-by: Pavan Nikhilesh <pbhagavatula at marvell.com>

Acked-by: Jerin Jacob <jerinj at marvell.com>

> ---
>  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 | 35 ++++++++++++++++++++++++----
>  1 file changed, 30 insertions(+), 5 deletions(-)
>
> diff --git a/doc/guides/linux_gsg/enable_func.rst b/doc/guides/linux_gsg/enable_func.rst
> index 1df3ab0255..c989674422 100644
> --- a/doc/guides/linux_gsg/enable_func.rst
> +++ b/doc/guides/linux_gsg/enable_func.rst
> @@ -90,16 +90,41 @@ 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
> +         https://www.kernel.org/doc/html/latest/timers/no_hz.html
> +         https://www.kernel.org/doc/html/latest/core-api/irq/
> +         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::
> +
> +   https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/cpusets.html
> +
> +Systemd (CPUAffinity)::
> +
> +   https://www.freedesktop.org/software/systemd/man/systemd.exec.html
> +
> +Also, see::
> +
> +   https://man7.org/linux/man-pages/man7/cpuset.7.html
> +   https://www.suse.com/c/cpu-isolation-practical-example-part-5/
> +   https://www.rcannings.com/systemd-core-isolation/
>
>  .. _High_Precision_Event_Timer:
>
> --
> 2.25.1
>