Re: [PATCH] Kbuild: Update config_data.gz only if KCONFIG_CONFIG materially changed
On 4/2/2021 10:11 PM, Masahiro Yamada wrote: On Fri, Apr 2, 2021 at 7:45 AM Elliot Berman wrote: 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 filechk to compare the existing config_data.gz and update only if it changed. 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. Signed-off-by: Elliot Berman --- kernel/Makefile | 2 +- scripts/Makefile.lib | 2 ++ 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/Makefile b/kernel/Makefile index 320f1f3..bd4e558 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -140,7 +140,7 @@ $(obj)/configs.o: $(obj)/config_data.gz targets += config_data.gz $(obj)/config_data.gz: $(KCONFIG_CONFIG) FORCE - $(call if_changed,gzip) + $(call filechk,gzip) I do not think this is the right approach because gzip is executed every time, even if the time stamp is not changed. Since .config is relatively small, gzip was quickly producing the same binary in multiple runs on my host. I thought about following gen_ikheaders.sh approach of comparing the md5sum, but I felt it was more complex than using filechk and re-compressing every time. I'll send a v2 tomorrow which follows gen_ikheaders.sh approach. $(obj)/kheaders.o: $(obj)/kheaders_data.tar.xz diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index a4fbaf8..81d3ec1 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -282,6 +282,8 @@ cmd_objcopy = $(OBJCOPY) $(OBJCOPYFLAGS) $(OBJCOPYFLAGS_$(@F)) $< $@ quiet_cmd_gzip = GZIP$@ cmd_gzip = cat $(real-prereqs) | $(KGZIP) -n -f -9 > $@ +filechk_gzip = cat $(real-prereqs) | $(KGZIP) -n -f -9 + # DTC # --- DTC ?= $(objtree)/scripts/dtc/dtc -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
Re: [PATCH] Kbuild: Update config_data.gz only if KCONFIG_CONFIG materially changed
On Fri, Apr 2, 2021 at 7:45 AM Elliot Berman wrote: > > 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 filechk to compare the existing > config_data.gz and update only if it changed. > > 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. > > Signed-off-by: Elliot Berman > --- > kernel/Makefile | 2 +- > scripts/Makefile.lib | 2 ++ > 2 files changed, 3 insertions(+), 1 deletion(-) > > diff --git a/kernel/Makefile b/kernel/Makefile > index 320f1f3..bd4e558 100644 > --- a/kernel/Makefile > +++ b/kernel/Makefile > @@ -140,7 +140,7 @@ $(obj)/configs.o: $(obj)/config_data.gz > > targets += config_data.gz > $(obj)/config_data.gz: $(KCONFIG_CONFIG) FORCE > - $(call if_changed,gzip) > + $(call filechk,gzip) I do not think this is the right approach because gzip is executed every time, even if the time stamp is not changed. > > $(obj)/kheaders.o: $(obj)/kheaders_data.tar.xz > > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib > index a4fbaf8..81d3ec1 100644 > --- a/scripts/Makefile.lib > +++ b/scripts/Makefile.lib > @@ -282,6 +282,8 @@ cmd_objcopy = $(OBJCOPY) $(OBJCOPYFLAGS) > $(OBJCOPYFLAGS_$(@F)) $< $@ > quiet_cmd_gzip = GZIP$@ >cmd_gzip = cat $(real-prereqs) | $(KGZIP) -n -f -9 > $@ > > +filechk_gzip = cat $(real-prereqs) | $(KGZIP) -n -f -9 > + > # DTC > # --- > DTC ?= $(objtree)/scripts/dtc/dtc > -- > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, > a Linux Foundation Collaborative Project > -- Best Regards Masahiro Yamada
[PATCH] Kbuild: Update config_data.gz only if KCONFIG_CONFIG materially changed
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 filechk to compare the existing config_data.gz and update only if it changed. 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. Signed-off-by: Elliot Berman --- kernel/Makefile | 2 +- scripts/Makefile.lib | 2 ++ 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/Makefile b/kernel/Makefile index 320f1f3..bd4e558 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -140,7 +140,7 @@ $(obj)/configs.o: $(obj)/config_data.gz targets += config_data.gz $(obj)/config_data.gz: $(KCONFIG_CONFIG) FORCE - $(call if_changed,gzip) + $(call filechk,gzip) $(obj)/kheaders.o: $(obj)/kheaders_data.tar.xz diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index a4fbaf8..81d3ec1 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -282,6 +282,8 @@ cmd_objcopy = $(OBJCOPY) $(OBJCOPYFLAGS) $(OBJCOPYFLAGS_$(@F)) $< $@ quiet_cmd_gzip = GZIP$@ cmd_gzip = cat $(real-prereqs) | $(KGZIP) -n -f -9 > $@ +filechk_gzip = cat $(real-prereqs) | $(KGZIP) -n -f -9 + # DTC # --- DTC ?= $(objtree)/scripts/dtc/dtc -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
