This patchset add a new helper, bpf_loop. One of the complexities of using for loops in bpf programs is that the verifier needs to ensure that in every possibility of the loop logic, the loop will always terminate. As such, there is a limit on how many iterations the loop can do. The bpf_loop helper moves the loop logic into the kernel and can thereby guarantee that the loop will always terminate. The bpf_loop helper simplifies a lot of the complexity the verifier needs to check, as well as removes the constraint on the number of loops able to be run. >From the test results, we see that using bpf_loop in place of the traditional for loop led to a decrease in verification time and number of bpf instructions by ~99%. The benchmark results show that as the number of iterations increases, the overhead per iteration decreases. The high-level overview of the patches - Patch 1 - kernel-side + API changes for adding bpf_loop Patch 2 - tests Patch 3 - use bpf_loop in strobemeta + pyperf600 and measure verifier performance Patch 4 - benchmark for throughput + latency of bpf_loop call v3 -> v4: ~ Address nits: use usleep for triggering bpf programs, fix copyright style v2 -> v3: ~ Rerun benchmarks on physical machine, update results ~ Propagate original error codes in the verifier v1 -> v2: ~ Change helper name to bpf_loop (instead of bpf_for_each) ~ Set max nr_loops (~8 million loops) for bpf_loop call ~ Split tests + strobemeta/pyperf600 changes into two patches ~ Add new ops_report_final helper for outputting throughput and latency Joanne Koong (4): bpf: Add bpf_loop helper selftests/bpf: Add bpf_loop test selftests/bpf: Measure bpf_loop verifier performance selftest/bpf/benchs: Add bpf_loop benchmark include/linux/bpf.h | 1 + include/uapi/linux/bpf.h | 25 +++ kernel/bpf/bpf_iter.c | 35 +++++ kernel/bpf/helpers.c | 2 + kernel/bpf/verifier.c | 88 +++++++---- tools/include/uapi/linux/bpf.h | 25 +++ tools/testing/selftests/bpf/Makefile | 4 +- tools/testing/selftests/bpf/bench.c | 37 +++++ tools/testing/selftests/bpf/bench.h | 2 + .../selftests/bpf/benchs/bench_bpf_loop.c | 105 +++++++++++++ .../bpf/benchs/run_bench_bpf_loop.sh | 15 ++ .../selftests/bpf/benchs/run_common.sh | 15 ++ .../selftests/bpf/prog_tests/bpf_loop.c | 145 ++++++++++++++++++ .../bpf/prog_tests/bpf_verif_scale.c | 12 ++ tools/testing/selftests/bpf/progs/bpf_loop.c | 112 ++++++++++++++ .../selftests/bpf/progs/bpf_loop_bench.c | 26 ++++ tools/testing/selftests/bpf/progs/pyperf.h | 71 ++++++++- .../selftests/bpf/progs/pyperf600_bpf_loop.c | 6 + .../testing/selftests/bpf/progs/strobemeta.h | 75 ++++++++- .../selftests/bpf/progs/strobemeta_bpf_loop.c | 9 ++ 20 files changed, 771 insertions(+), 39 deletions(-) create mode 100644 tools/testing/selftests/bpf/benchs/bench_bpf_loop.c create mode 100755 tools/testing/selftests/bpf/benchs/run_bench_bpf_loop.sh create mode 100644 tools/testing/selftests/bpf/prog_tests/bpf_loop.c create mode 100644 tools/testing/selftests/bpf/progs/bpf_loop.c create mode 100644 tools/testing/selftests/bpf/progs/bpf_loop_bench.c create mode 100644 tools/testing/selftests/bpf/progs/pyperf600_bpf_loop.c create mode 100644 tools/testing/selftests/bpf/progs/strobemeta_bpf_loop.c -- 2.30.2
