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 <eberman@xxxxxxxxxxxxxx> --- 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