Changeset 5365c7a for chapter04/aboutsbus.xml

Timestamp:

09/03/2024 04:45:55 PM (3 weeks ago)

Author:

Xi Ruoyao <xry111@…>

Branches:

xry111/mips64el

Children:

7b85e11

Parents:

1e1cb39 (diff), f2c8c6e (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:

Merge remote-tracking branch 'origin/trunk' into xry111/mips64el

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>
 
@@ -36 +36 @@
   to give an estimate of how long it might take to install a package, but the
   numbers can vary by as much as dozens of minutes in some cases.</para>
+
+  <para>On some newer systems, the motherboard is capable of controlling 
+  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 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>If <command>powerprofilesctl</command> is available, issue the
+  <command>powerprofilesctl set performance</command> command to select
+  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>
@@ -45 +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>
-
   </note>