On Sat, Apr 24, 2021 at 2:02 AM Elliot Berman <eberman@xxxxxxxxxxxxxx> wrote: Sorry for the delay. This patch is over-engineering. I will apply this. https://patchwork.kernel.org/project/linux-kbuild/patch/20210425062407.1183801-5-masahiroy@xxxxxxxxxx/ The 'cmp' command is not expensive. md5sum is unneeded. > If you update the timestamp of KCONFIG_CONFIG without actually changing > anything, config_data.gz is re-generated and causes vmlinux to re-link. > When Link Time Optimization is enabled, unnecessary re-linking of > vmlinux is highly desirable since it adds several minutes to build time. > > Avoid touching config_data.gz by using a script to compare the existing > config_data.gz, KCONFIG_CONFIG, or script itself to update only if any > is mismatched. The script follows gen_kheaders.sh approach for > determing in update is needed. The script intentionally avoids > re-compressing KCONFIG_CONFIG. > > The .config can be touched, for instance, by a build script which > installs the default defconfig and then applies a defconfig fragment on > top. > > For a simple example on my x86 machine, I modified x86 default defconfig to set > CONFIG_IKCONFIG=y and run: > make -j50 defconfig tiny.config vmlinux > make -j50 defconfig tiny.config vmlinux > With this patch, vmlinux is not re-built as a result of config_data.gz > change. > > Changes in v2: > - Use md5 checksum to compare .config instead of gzip'ing again > > Signed-off-by: Elliot Berman <eberman@xxxxxxxxxxxxxx> > --- > kernel/.gitignore | 1 + > kernel/Makefile | 4 +++- > kernel/gen_config_data.sh | 31 +++++++++++++++++++++++++++++++ > 3 files changed, 35 insertions(+), 1 deletion(-) > create mode 100755 kernel/gen_config_data.sh > > diff --git a/kernel/.gitignore b/kernel/.gitignore > index 78701ea..a191136 100644 > --- a/kernel/.gitignore > +++ b/kernel/.gitignore > @@ -1,4 +1,5 @@ > # SPDX-License-Identifier: GPL-2.0-only > +config_data.gz.md5 > kheaders.md5 > timeconst.h > hz.bc > diff --git a/kernel/Makefile b/kernel/Makefile > index 320f1f3..0784bf3d 100644 > --- a/kernel/Makefile > +++ b/kernel/Makefile > @@ -139,8 +139,10 @@ obj-$(CONFIG_SCF_TORTURE_TEST) += scftorture.o > $(obj)/configs.o: $(obj)/config_data.gz > > targets += config_data.gz > +quiet_cmd_genicfg = CHK $(obj)/config_data.gz > + cmd_genicfg = $(CONFIG_SHELL) $(srctree)/kernel/gen_config_data.sh $@ $< > $(obj)/config_data.gz: $(KCONFIG_CONFIG) FORCE > - $(call if_changed,gzip) > + $(call cmd,genicfg) > > $(obj)/kheaders.o: $(obj)/kheaders_data.tar.xz > > diff --git a/kernel/gen_config_data.sh b/kernel/gen_config_data.sh > new file mode 100755 > index 00000000..e9ff193 > --- /dev/null > +++ b/kernel/gen_config_data.sh > @@ -0,0 +1,31 @@ > +#!/bin/sh > +# SPDX-License-Identifier: GPL-2.0 > + > +# This script generates a compressed version of .config, if its checksum has changed > +set -e > + > +this_file="$(readlink -f "$0")" > +outfile=$1 > +infile=$2 > + > +config_md5="$(md5sum $infile | cut -d ' ' -f1)" > +# Any changes to this script will also cause a rebuild of config_data. > +this_file_md5="$(md5sum $sfile | cut -d ' ' -f1)" > +if [ -f $outfile ]; then outfile_md5="$(md5sum $outfile | cut -d ' ' -f1)"; fi > + > +if [ -f $outfile.md5 ] && > + [ "$(head -n 1 $outfile.md5)" = "$config_md5" ] && > + [ "$(head -n 2 $outfile.md5 | tail -n 1)" = "$this_file_md5" ] && > + [ "$(tail -n 1 $outfile.md5)" = "$outfile_md5" ]; then > + exit > +fi > + > +if [ "${quiet}" != "silent_" ]; then > + echo " GEN $outfile" > +fi > + > +${KGZIP} -c -n -f -9 $infile > $outfile > + > +echo "$config_md5" > $outfile.md5 > +echo "$this_file_md5" >> $outfile.md5 > +echo "$(md5sum $outfile | cut -d ' ' -f1)" >> $outfile.md5 > -- > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, > a Linux Foundation Collaborative Project > -- Best Regards Masahiro Yamada
