Changeset d2eb97b for chapter04

Timestamp:

08/27/2024 10:30:14 PM (7 weeks ago)

Author:

Thomas Trepl <thomas@…>

Branches:

multilib, xry111/multilib

Children:

f33eca9

Parents:

3eb188e (diff), 2b76c89 (diff)
Note: this is a merge changeset, the changes displayed below correspond to the merge itself.
Use the (diff) links above to see all the changes relative to each parent.

Message:

Automatic merge of trunk into multilib

File:

• chapter04/aboutsbus.xml (modified) (3 diffs)

chapter04/aboutsbus.xml

@@ -27 +27 @@
 
   <para>For example, consider a package whose compilation time is 4.5
-  SBUs. This means that if your system took 10 minutes to compile and
+  SBUs. This means that if your system took 4 minutes to compile and
   install the first pass of binutils, it will take
-  <emphasis>approximately</emphasis> 45 minutes to build the example package.
+  <emphasis>approximately</emphasis> 18 minutes to build the example package.
   Fortunately, most build times are shorter than one SBU.</para>
 
@@ -37 +37 @@
   numbers can vary by as much as dozens of minutes in some cases.</para>
 
-  <para>Before measuring the build time of any package (no matter Binutils
-  pass 1 or a package of which the SBU is being measured), make sure a
-  system power profile suitable to make the system running with the
-  maximum performance (and the maximum power consumption) is selected.  Or
-  the measured SBU value may be severly inaccurate because the system may be
-  operated differently building Binutils pass 1 and the other package.
+  <para>On some newer systems, the motherboard is capable of contolling 
+  the system clock speed. This can be controlled with a command such as
+  <command>powerprofilesctl</command>. This is not available in LFS, but 
+  may be available on the host distro. After LFS is complete, it can be
+  added to a system with the procedures at the
+  <ulink url='&blfs-book;sysutils/power-profiles-daemon.html'>
+  BLFS power-profiles-daemon</ulink> page.
+
+  Before measuring the build time of any package it is advisable to use a
+  system power profile set for maximum performance (and maximum power 
+  consumption). 
+
+  Otherwise the measured SBU value may be inaccurate because the 
+  system may react differently when building <xref linkend='ch-tools-binutils-pass1'/>
+  or other packages.
+
   Be aware that a significant inaccuracy can still show up even if the same
-  profile (except one maximizing the performance) is used for both packages:
-  the system may respond slower for <quote>saving the power</quote> building
-  Binutils pass 1, because the system load seems only about 25% of the load
-  building the other package (with <parameter>-j4</parameter>).</para>
+  profile is used for both packages because the system may respond slower if
+  the system is idle when starting the build procedure. Setting the power
+  profile to <quote>performance</quote> will minimize this problem.  And
+  obviously doing so will also make the system build LFS faster.</para>
 
-  <para>On most distros the power profile can be managed with either
-  <command>power-profiles-daemon</command> or <command>tuned</command>.
-  If the distro runs <command>power-profiles-daemon</command>, issue the
+  <para>If <command>powerprofilesctl</command> is available, issue the
   <command>powerprofilesctl set performance</command> command to select
-  the <literal>performance</literal> profile.  If the distro runs
-  <command>tuned</command>, issue the <command>tuned-adm profile
-  throughput-performance</command> command to select the
-  <literal>throughput-performance</literal> profile.</para>
-
-  <para>Even if you are not measuring the SBU values, it's still better to
-  select the power profile for maximum performance before building LFS, as
-  doing so can (obviously) make the system faster to build LFS
-  packages.</para>
+  the <literal>performance</literal> profile.  Some distros provides the
+  <command>tuned-adm</command> command for managing the profiles instead of
+  <command>powerprofilesctl</command>, on these distros issue the
+  <command>tuned-adm profile throughput-performance</command> command to
+  select the <literal>throughput-performance</literal> profile.</para>
 
   <note>
@@ -71 +75 @@
     single processor build to properly analyze the error messages.</para>
 
-    <para>The times presented here are based upon using four cores (-j4). The
+    <para>The times presented here for all packages 
+    (except <xref linkend='ch-tools-binutils-pass1'/> which is based on one core)
+    are based upon using four cores (-j4). The
     times in Chapter 8 also include the time to run the regression tests for
     the package unless specified otherwise.</para>