Added build hack to enforce Intel's "Turbo Boost". This should be harmless for single/virtual core processors. Now 'make' is always invoked with number of jobs higher than the available CPU cores.

src/.config

@@ -137,3 +137,10 @@ COPY_SOURCE_ISO=true
 # is 'true' for demonstration purposes.
 USE_BOOT_LOGO=true
 
+# This property is the multiplicator which is used during the build process. The
+# total number of each 'make' jobs will be equal to the number of detected CPU
+# cores mutiplied by this property. For example, if your CPU has 4 cores, then
+# the number of 'make' jobs will be 4 * 2 = 8. Don't change this value unless
+# you know what 'make' jobs are! 
+JOB_FACTOR=2
+

src/02_build_kernel.sh

@@ -4,6 +4,15 @@ echo "*** BUILD KERNEL BEGIN ***"
 
 SRC_DIR=$(pwd)
 
+# Read the 'JOB_FACTOR' property from '.config'
+JOB_FACTOR="$(grep -i ^JOB_FACTOR .config | cut -f2 -d'=')"
+
+# Find the number of available CPU cores.
+NUM_CORES=$(grep ^processor /proc/cpuinfo | wc -l)
+
+# Calculate the number of 'make' jobs to be used later.
+NUM_JOBS=$((NUM_CORES * JOB_FACTOR))
+
 cd work/kernel
 
 # Change to the kernel source directory which ls finds, e.g. 'linux-4.4.6'.
@@ -11,7 +20,7 @@ cd $(ls -d linux-*)
 
 # Cleans up the kernel sources, including configuration files.
 echo "Preparing kernel work area..."
-make mrproper
+make mrproper -j $NUM_JOBS
 
 # Read the 'USE_PREDEFINED_KERNEL_CONFIG' property from '.config'
 USE_PREDEFINED_KERNEL_CONFIG="$(grep -i ^USE_PREDEFINED_KERNEL_CONFIG $SRC_DIR/.config | cut -f2 -d'=')"
@@ -27,7 +36,7 @@ if [ "$USE_PREDEFINED_KERNEL_CONFIG" = "true" ] ; then
   cp -f $SRC_DIR/minimal_config/kernel.config .config
 else
   # Create default configuration file for the kernel.
-  make defconfig
+  make defconfig -j $NUM_JOBS
   echo "Generated default kernel configuration."
 
   # Changes the name of the system to 'minimal'.
@@ -66,12 +75,12 @@ fi
 echo "Building kernel..."
 make \
   CFLAGS="-Os -s -fno-stack-protector -U_FORTIFY_SOURCE" \
-  bzImage -j $(grep ^processor /proc/cpuinfo | wc -l)
+  bzImage -j $NUM_JOBS
 
 # Install kernel headers in './usr' (this is not '/usr') which are used later
 # when we build and configure the GNU C library (glibc).
 echo "Generating kernel headers..."
-make headers_install
+make headers_install -j $NUM_JOBS
 
 cd $SRC_DIR
 

src/04_build_glibc.sh

@@ -4,6 +4,15 @@ echo "*** BUILD GLIBC BEGIN ***"
 
 SRC_DIR=$(pwd)
 
+# Read the 'JOB_FACTOR' property from '.config'
+JOB_FACTOR="$(grep -i ^JOB_FACTOR .config | cut -f2 -d'=')"
+
+# Find the number of available CPU cores.
+NUM_CORES=$(grep ^processor /proc/cpuinfo | wc -l)
+
+# Calculate the number of 'make' jobs to be used later.
+NUM_JOBS=$((NUM_CORES * JOB_FACTOR))
+
 # Find the kernel build directory.
 cd work/kernel
 cd $(ls -d linux-*)
@@ -48,13 +57,13 @@ $GLIBC_SRC/configure \
 
 # Compile glibc with optimization for "parallel jobs" = "number of processors".
 echo "Building glibc..."
-make -j $(grep ^processor /proc/cpuinfo | wc -l)
+make -j $NUM_JOBS
 
 # Install glibc in the installation area, e.g. 'work/glibc/glibc_installed'.
 echo "Installing glibc..."
 make install \
   DESTDIR=$GLIBC_INSTALLED \
-  -j $(grep ^processor /proc/cpuinfo | wc -l)
+  -j $NUM_JOBS
 
 cd $SRC_DIR
 

src/07_build_busybox.sh

@@ -4,6 +4,15 @@ echo "*** BUILD BUSYBOX BEGIN ***"
 
 SRC_DIR=$(pwd)
 
+# Read the 'JOB_FACTOR' property from '.config'
+JOB_FACTOR="$(grep -i ^JOB_FACTOR .config | cut -f2 -d'=')"
+
+# Find the number of available CPU cores.
+NUM_CORES=$(grep ^processor /proc/cpuinfo | wc -l)
+
+# Calculate the number of 'make' jobs to be used later.
+NUM_JOBS=$((NUM_CORES * JOB_FACTOR))
+
 # Remember the glibc installation area.
 GLIBC_PREPARED=$(pwd)/work/glibc/glibc_prepared
 
@@ -17,7 +26,7 @@ cd $(ls -d busybox-*)
 
 # Remove previously generated artifacts.
 echo "Preparing BusyBox work area. This may take a while..."
-make distclean
+make distclean -j $NUM_JOBS
 
 # Read the 'USE_PREDEFINED_BUSYBOX_CONFIG' property from '.config'
 USE_PREDEFINED_BUSYBOX_CONFIG="$(grep -i ^USE_PREDEFINED_BUSYBOX_CONFIG $SRC_DIR/.config | cut -f2 -d'=')"
@@ -34,7 +43,7 @@ if [ "$USE_PREDEFINED_BUSYBOX_CONFIG" = "true" ] ; then
 else
   # Create default configuration file.
   echo "Generating default BusyBox configuration..."  
-  make defconfig
+  make defconfig -j $NUM_JOBS
   
   # The 'inetd' applet fails to compile because we use the glibc installation area as
   # main pointer to the kernel headers (see 05_prepare_glibc.sh) and some headers are
@@ -53,13 +62,13 @@ sed -i "s/.*CONFIG_SYSROOT.*/CONFIG_SYSROOT=$GLIBC_PREPARED_ESCAPED/" .config
 echo "Building BusyBox..."
 make \
   EXTRA_CFLAGS="-Os -s -fno-stack-protector -U_FORTIFY_SOURCE" \
-  busybox -j $(grep ^processor /proc/cpuinfo | wc -l)
+  busybox -j $NUM_JOBS
 
 # Create the symlinks for busybox. The file 'busybox.links' is used for this.
 echo "Generating BusyBox based initramfs area..."
 make \
   CONFIG_PREFIX="../busybox_installed" \
-  install
+  install -j $NUM_JOBS
 
 cd $SRC_DIR
 

src/overlay_dropbear_02_build.sh

@@ -2,6 +2,15 @@
 
 SRC_DIR=$(pwd)
 
+# Read the 'JOB_FACTOR' property from '.config'
+JOB_FACTOR="$(grep -i ^JOB_FACTOR .config | cut -f2 -d'=')"
+
+# Find the number of available CPU cores.
+NUM_CORES=$(grep ^processor /proc/cpuinfo | wc -l)
+
+# Calculate the number of 'make' jobs to be used later.
+NUM_JOBS=$((NUM_CORES * JOB_FACTOR))
+
 if [ ! -d $SRC_DIR/work/glibc/glibc_prepared ] ; then
   echo "Cannot continue - Dropbear SSH depends on GLIBC. Please buld GLIBC first."
   exit 1
@@ -13,7 +22,7 @@ cd work/overlay/dropbear
 cd $(ls -d dropbear-*)
 
 echo "Preparing Dropbear work area. This may take a while..."
-make clean 2>/dev/null
+make clean -j $NUM_JOBS 2>/dev/null
 
 rm -rf ../dropbear_installed
 
@@ -25,10 +34,10 @@ echo "Configuring Dropbear..."
   CFLAGS="-Os -s -fno-stack-protector -U_FORTIFY_SOURCE"
 
 echo "Building Dropbear..."
-make
+make -j $NUM_JOBS
 
 echo "Installing Dropbear..."
-make install
+make install -j $NUM_JOBS
 
 mkdir -p ../dropbear_installed/lib
 

src/overlay_links_02_build.sh

@@ -2,13 +2,22 @@
 
 SRC_DIR=$(pwd)
 
+# Read the 'JOB_FACTOR' property from '.config'
+JOB_FACTOR="$(grep -i ^JOB_FACTOR .config | cut -f2 -d'=')"
+
+# Find the number of available CPU cores.
+NUM_CORES=$(grep ^processor /proc/cpuinfo | wc -l)
+
+# Calculate the number of 'make' jobs to be used later.
+NUM_JOBS=$((NUM_CORES * JOB_FACTOR))
+
 cd work/overlay/links
 
 # Change to the Links source directory which ls finds, e.g. 'links-2.12'.
 cd $(ls -d links-*)
 
 echo "Preparing Links work area. This may take a while..."
-make clean 2>/dev/null
+make clean -j $NUM_JOBS 2>/dev/null
 
 rm -rf ../links_installed
 
@@ -25,10 +34,10 @@ echo "Configuring Links..."
 sed -i "s/^CFLAGS = .*/CFLAGS = \\-Os \\-s \\-fno\\-stack\\-protector \\-U_FORTIFY_SOURCE/" Makefile
 
 echo "Building Links..."
-make
+make -j $NUM_JOBS
 
 echo "Installing Links..."
-make install
+make install -j $NUM_JOBS
 
 echo "Reducing Links size..."
 strip -g ../links_installed/bin/* 2>/dev/null