On Fri, Nov 15, 2024 at 11:49 AM Vadim Fedorenko <vadfed@xxxxxxxx> wrote: > > This patchset adds 2 kfuncs to provide a way to precisely measure the > time spent running some code. The first patch provides a way to get cpu > cycles counter which is used to feed CLOCK_MONOTONIC_RAW. On x86 > architecture it is effectively rdtsc_ordered() function while on other > architectures it falls back to __arch_get_hw_counter(). The second patch > adds a kfunc to convert cpu cycles to nanoseconds using shift/mult > constants discovered by kernel. JIT version is done for x86 for now, on > other architectures it falls back to slightly simplified version of > vdso_calc_ns. > > Selftests are also added to check whether the JIT implementation is > correct and to show the simplest usage example. > > Change log: > v5 -> v6: > * added cover letter > * add comment about dropping S64_MAX manipulation in jitted > implementation of rdtsc_oredered (Alexey) > * add comment about using 'lfence;rdtsc' variant (Alexey) > * change the check in fixup_kfunc_call() (Eduard) > * make __arch_get_hw_counter() call more aligned with vDSO > implementation (Yonghong) > v4 -> v5: > * use #if instead of #ifdef with IS_ENABLED > v3 -> v4: > * change name of the helper to bpf_get_cpu_cycles (Andrii) > * Hide the helper behind CONFIG_GENERIC_GETTIMEOFDAY to avoid exposing > it on architectures which do not have vDSO functions and data > * reduce the scope of check of inlined functions in verifier to only 2, > which are actually inlined. > * change helper name to bpf_cpu_cycles_to_ns. > * hide it behind CONFIG_GENERIC_GETTIMEOFDAY to avoid exposing on > unsupported architectures. > v2 -> v3: > * change name of the helper to bpf_get_cpu_cycles_counter to > * explicitly mention what counter it provides (Andrii) > * move kfunc definition to bpf.h to use it in JIT. > * introduce another kfunc to convert cycles into nanoseconds as > * more meaningful time units for generic tracing use case (Andrii) > v1 -> v2: > * Fix incorrect function return value type to u64 > * Introduce bpf_jit_inlines_kfunc_call() and use it in > mark_fastcall_pattern_for_call() to avoid clobbering in case > of running programs with no JIT (Eduard) > * Avoid rewriting instruction and check function pointer directly > in JIT (Alexei) > * Change includes to fix compile issues on non x86 architectures > > Vadim Fedorenko (4): > bpf: add bpf_get_cpu_cycles kfunc > bpf: add bpf_cpu_cycles_to_ns helper > selftests/bpf: add selftest to check rdtsc jit > selftests/bpf: add usage example for cpu cycles kfuncs > > arch/x86/net/bpf_jit_comp.c | 60 ++++++++++ > arch/x86/net/bpf_jit_comp32.c | 33 ++++++ > include/linux/bpf.h | 6 + > include/linux/filter.h | 1 + > kernel/bpf/core.c | 11 ++ > kernel/bpf/helpers.c | 32 ++++++ > kernel/bpf/verifier.c | 41 ++++++- > .../bpf/prog_tests/test_cpu_cycles.c | 35 ++++++ > .../selftests/bpf/prog_tests/verifier.c | 2 + > .../selftests/bpf/progs/test_cpu_cycles.c | 25 +++++ > .../selftests/bpf/progs/verifier_cpu_cycles.c | 104 ++++++++++++++++++ > 11 files changed, 344 insertions(+), 6 deletions(-) > create mode 100644 tools/testing/selftests/bpf/prog_tests/test_cpu_cycles.c > create mode 100644 tools/testing/selftests/bpf/progs/test_cpu_cycles.c > create mode 100644 tools/testing/selftests/bpf/progs/verifier_cpu_cycles.c > > -- > 2.43.5 > typo in subject: kfuncss -> kfuncs LGTM overall, thanks a lot for adding this! For the series: Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
