> On Feb 29, 2020, at 7:52 PM, Yonghong Song <yhs@xxxxxx> wrote: > > > > On 2/28/20 3:40 PM, Song Liu wrote: >> With fentry/fexit programs, it is possible to profile BPF program with >> hardware counters. Introduce bpftool "prog profile", which measures key >> metrics of a BPF program. >> bpftool prog profile command creates per-cpu perf events. Then it attaches >> fentry/fexit programs to the target BPF program. The fentry program saves >> perf event value to a map. The fexit program reads the perf event again, >> and calculates the difference, which is the instructions/cycles used by >> the target program. >> Example input and output: >> ./bpftool prog profile 3 id 337 cycles instructions llc_misses >> 4228 run_cnt >> 3403698 cycles (84.08%) >> 3525294 instructions # 1.04 insn per cycle (84.05%) >> 13 llc_misses # 3.69 LLC misses per million isns (83.50%) >> This command measures cycles and instructions for BPF program with id >> 337 for 3 seconds. The program has triggered 4228 times. The rest of the >> output is similar to perf-stat. In this example, the counters were only >> counting ~84% of the time because of time multiplexing of perf counters. >> Note that, this approach measures cycles and instructions in very small >> increments. So the fentry/fexit programs introduce noticeable errors to >> the measurement results. >> The fentry/fexit programs are generated with BPF skeletons. Therefore, we >> build bpftool twice. The first time _bpftool is built without skeletons. >> Then, _bpftool is used to generate the skeletons. The second time, bpftool >> is built with skeletons. >> Signed-off-by: Song Liu <songliubraving@xxxxxx> >> --- >> tools/bpf/bpftool/Makefile | 18 + >> tools/bpf/bpftool/prog.c | 428 +++++++++++++++++++++- >> tools/bpf/bpftool/skeleton/profiler.bpf.c | 171 +++++++++ >> tools/bpf/bpftool/skeleton/profiler.h | 47 +++ >> tools/scripts/Makefile.include | 1 + >> 5 files changed, 664 insertions(+), 1 deletion(-) >> create mode 100644 tools/bpf/bpftool/skeleton/profiler.bpf.c >> create mode 100644 tools/bpf/bpftool/skeleton/profiler.h >> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile >> index c4e810335810..c035fc107027 100644 >> --- a/tools/bpf/bpftool/Makefile >> +++ b/tools/bpf/bpftool/Makefile >> @@ -59,6 +59,7 @@ LIBS = $(LIBBPF) -lelf -lz >> INSTALL ?= install >> RM ?= rm -f >> +CLANG ?= clang >> FEATURE_USER = .bpftool >> FEATURE_TESTS = libbfd disassembler-four-args reallocarray zlib >> @@ -110,6 +111,22 @@ SRCS += $(BFD_SRCS) >> endif >> OBJS = $(patsubst %.c,$(OUTPUT)%.o,$(SRCS)) $(OUTPUT)disasm.o >> +_OBJS = $(filter-out $(OUTPUT)prog.o,$(OBJS)) $(OUTPUT)_prog.o >> + >> +$(OUTPUT)_prog.o: prog.c >> + $(QUIET_CC)$(COMPILE.c) -MMD -DBPFTOOL_WITHOUT_SKELETONS -o $@ $< >> + >> +$(OUTPUT)_bpftool: $(_OBJS) $(LIBBPF) >> + $(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $(_OBJS) $(LIBS) >> + >> +skeleton/profiler.bpf.o: skeleton/profiler.bpf.c >> + $(QUIET_CLANG)$(CLANG) -g -O2 -target bpf -c $< -o $@ > > With a fresh checkout, applying this patch and just selftests like > make -C tools/testing/selftests/bpf > > I got the following build error: > > make[2]: Leaving directory `/data/users/yhs/work/net-next/tools/lib/bpf' > clang -g -O2 -target bpf -c skeleton/profiler.bpf.c -o skeleton/profiler.bpf.o > skeleton/profiler.bpf.c:5:10: fatal error: 'bpf/bpf_helpers.h' file not found > #include <bpf/bpf_helpers.h> > ^~~~~~~~~~~~~~~~~~~ > 1 error generated. > make[1]: *** [skeleton/profiler.bpf.o] Error 1 > > I think Makefile should be tweaked to avoid selftest failure. Hmm... I am not seeing this error. The build succeeded in the test. Thanks, Song
