On 12/12/24 4:32 PM, Eduard Zingerman wrote:
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>
LGTM except should target to bpf-next.
Acked-by: Yonghong Song <yonghong.song@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:%-=%))
