BPF_TARGET_ENDIAN is used in CLANG_BPF_BUILD_RULE and co macros. It is defined as a recursively expanded variable, meaning that it is recomputed each time the value is needed. Thus, it is recomputed for each *.bpf.o file compilation. The variable is computed by running a C compiler in a shell. This significantly hinders parallel build performance for *.bpf.o files. This commit changes BPF_TARGET_ENDIAN to be a simply expanded variable. # Build performance stats before this commit $ git clean -xfd; time make -j12 real 1m0.000s ... # Build performance stats after this commit $ git clean -xfd; time make -j12 real 0m43.605s ... Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx> --- tools/testing/selftests/bpf/Makefile | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile index bb8cf8f5bf11..9e870e519c30 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -461,10 +461,10 @@ $(shell $(1) $(2) -dM -E - </dev/null | grep -E 'MIPS(EL|EB)|_MIPS_SZ(PTR|LONG) endef # Determine target endianness. -IS_LITTLE_ENDIAN = $(shell $(CC) -dM -E - </dev/null | \ +IS_LITTLE_ENDIAN := $(shell $(CC) -dM -E - </dev/null | \ grep 'define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__') -MENDIAN=$(if $(IS_LITTLE_ENDIAN),-mlittle-endian,-mbig-endian) -BPF_TARGET_ENDIAN=$(if $(IS_LITTLE_ENDIAN),--target=bpfel,--target=bpfeb) +MENDIAN:=$(if $(IS_LITTLE_ENDIAN),-mlittle-endian,-mbig-endian) +BPF_TARGET_ENDIAN:=$(if $(IS_LITTLE_ENDIAN),--target=bpfel,--target=bpfeb) ifneq ($(CROSS_COMPILE),) CLANG_TARGET_ARCH = --target=$(notdir $(CROSS_COMPILE:%-=%)) -- 2.47.0