GCC 9 introduces a new option, -flive-patching. It disables certain optimizations which could make a compilation unsafe for later live patching of the running kernel. The option is used only if CONFIG_LIVEPATCH is enabled and $(CC) supports it. Performance impact of the option was measured on three different Intel machines - two bigger NUMA boxes and one smaller UMA box. Kernel intensive (IO, scheduling, networking) benchmarks were selected, plus a set of HPC workloads from NAS Parallel Benchmark. The tests were done on upstream kernel 5.0-rc8 with openSUSE Leap 15.0 userspace. The majority of the tests is unaffected. The only significant exception is the scheduler section which suffers 1-3% degradation. Evaluated-by: Giovanni Gherdovich <ggherdovich@xxxxxxx> Signed-off-by: Miroslav Benes <mbenes@xxxxxxx> --- The patch is based on master branch of the livepatching tree on git.kernel.org. Many thanks to Giovanni who ran the whole testing campaign and analyzed the results. I archived the dashboard and detailed data. If anyone is interested, we could probably set up a public website somewhere. Makefile | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/Makefile b/Makefile index f070e0d65186..464a693a22e9 100644 --- a/Makefile +++ b/Makefile @@ -789,6 +789,10 @@ KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections LDFLAGS_vmlinux += --gc-sections endif +ifdef CONFIG_LIVEPATCH +KBUILD_CFLAGS += $(call cc-option, -flive-patching=inline-clone) +endif + # arch Makefile may override CC so keep this after arch Makefile is included NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include) -- 2.21.0
