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+<?xml version="1.0" encoding="ISO-8859-1"?>
+<!DOCTYPE section PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<section condition="f_ci" id="enea-linux-realtime-cpu-isolation">
+  <title>CPU Isolation</title>
+
+  <note>
+    <para>The level of feature support is target specific. Look up the <link
+    linkend="feature-matrix">Feature Compatibility Matrix</link> to see how
+    your target supports this feature.</para>
+  </note>
+
+  <para><emphasis role="bold">CPU isolation</emphasis><indexterm>
+      <primary>CPU isolation</primary>
+    </indexterm><indexterm>
+      <primary>isolation</primary>
+    </indexterm> facilitates predictable task scheduling, hence real-time
+  properties, by protecting SMP<indexterm>
+      <primary>SMP</primary>
+    </indexterm> CPUs<indexterm>
+      <primary>CPU</primary>
+    </indexterm> from being disturbed by unnecessary interrupts and unwanted
+  tasks. The isolated CPUs are granted a tickless environment, and are
+  excluded from load balancing. Any CPU except for CPU 0 can be
+  isolated.</para>
+
+  <para>Depending on the capabilities of the kernel for the specific target,
+  the isolated CPUs can obtain a tickless or nearly tickless environment. A
+  tickless environment means that isolated CPUs get no ticks at all (0 Hz).
+  Nearly tickless environment means that isolated CPUs are still disturbed by
+  ticks once a second (1 Hz).</para>
+
+  <para>The CPU isolation process involves several steps until a CPU is fully
+  isolated. Enea Linux simplifies this process for you by implementing in the
+  distribution kernel patching and configuration, and providing a script that
+  performs the partitioning in runtime.</para>
+
+  <orderedlist>
+    <listitem>
+      <para>Install <emphasis role="italic">partrt</emphasis> in Enea
+      Linux</para>
+    </listitem>
+
+    <listitem>
+      <para><phrase id="enea-linux-realtime-cpu-isolation-boot">Load and
+      boot</phrase> Enea Linux on target as described in the <link
+      linkend="enea-linux-target">Target Guide</link>, but also add the boot
+      parameters <literal>isolcpus</literal><indexterm>
+          <primary>isolcpus</primary>
+        </indexterm> and <literal>nohz</literal><indexterm>
+          <primary>nohz</primary>
+        </indexterm> telling which CPUs to isolate.</para>
+
+      <para>If booted by U-Boot:</para>
+
+      <programlisting>setenv bootargs &lt;other params&gt; <emphasis
+          role="bold">isolcpus=2,3 nohz_full=2,3</emphasis></programlisting>
+
+      <para>If booted by PXE:</para>
+
+      <programlisting>append &lt;other params&gt; <emphasis role="bold">isolcpus=2,3 nohz_full=2,3</emphasis></programlisting>
+    </listitem>
+
+    <listitem>
+      <para>After booting the Linux kernel, execute the <emphasis
+      role="bold">partrt</emphasis><indexterm>
+          <primary>partrt</primary>
+        </indexterm> script to create real-time partitions for the isolated
+      CPUs. Each CPU is coded as a binary number. The argument to partrt is an
+      OR-ed bit mask of the CPU/s to add to the real-time partition, here
+      0100<subscript>2</subscript> (CPU 2) OR 1000<subscript>2</subscript>
+      (CPU 3) = 1100<subscript>2</subscript> (0xc).</para>
+
+      <programlisting>$ partrt create 0xc</programlisting>
+
+      <para>CPUs 2 and 3 now provide an optimal real-time environment for your
+      application.</para>
+    </listitem>
+  </orderedlist>
+</section>
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