This patchset adds a new kind of bpf map: the bloom filter map. Bloom filters are a space-efficient probabilistic data structure used to quickly test whether an element exists in a set. For a brief overview about how bloom filters work, https://en.wikipedia.org/wiki/Bloom_filter may be helpful. One example use-case is an application leveraging a bloom filter map to determine whether a computationally expensive hashmap lookup can be avoided. If the element was not found in the bloom filter map, the hashmap lookup can be skipped. This patchset includes benchmarks for testing the performance of the bloom filter for different entry sizes and different number of hash functions used, as well as comparisons for hashmap lookups with vs. without the bloom filter. v2 -> v3: * Add libbpf changes for supporting nr_hash_funcs, instead of passing the number of hash functions through map_flags. * Separate the hashing logic in kernel/bpf/bloom_filter.c into a helper function v1 -> v2: * Remove libbpf changes, and pass the number of hash functions through map_flags instead. * Default to using 5 hash functions if no number of hash functions is specified. * Use set_bit instead of spinlocks in the bloom filter bitmap. This improved the speed significantly. For example, using 5 hash functions with 100k entries, there was roughly a 35% speed increase. * Use jhash2 (instead of jhash) for u32-aligned value sizes. This increased the speed by roughly 5 to 15%. When using jhash2 on value sizes non-u32 aligned (truncating any remainder bits), there was not a noticeable difference. * Add test for using the bloom filter as an inner map. * Reran the benchmarks, updated the commit messages to correspond to the new results. Joanne Koong (5): bpf: Add bloom filter map implementation libbpf: Allow the number of hashes in bloom filter maps to be configurable selftests/bpf: Add bloom filter map test cases bpf/benchs: Add benchmark test for bloom filter maps bpf/benchs: Add benchmarks for comparing hashmap lookups with vs. without bloom filter include/linux/bpf_types.h | 1 + include/uapi/linux/bpf.h | 6 +- kernel/bpf/Makefile | 2 +- kernel/bpf/bloom_filter.c | 185 +++++++++ kernel/bpf/syscall.c | 14 +- kernel/bpf/verifier.c | 19 +- tools/include/uapi/linux/bpf.h | 6 +- tools/lib/bpf/bpf.c | 2 + tools/lib/bpf/bpf.h | 1 + tools/lib/bpf/libbpf.c | 32 +- tools/lib/bpf/libbpf.h | 2 + tools/lib/bpf/libbpf.map | 1 + tools/lib/bpf/libbpf_internal.h | 4 +- tools/testing/selftests/bpf/Makefile | 4 +- tools/testing/selftests/bpf/bench.c | 57 ++- tools/testing/selftests/bpf/bench.h | 3 + .../bpf/benchs/bench_bloom_filter_map.c | 384 ++++++++++++++++++ .../bpf/benchs/run_bench_bloom_filter_map.sh | 43 ++ .../bpf/benchs/run_bench_ringbufs.sh | 30 +- .../selftests/bpf/benchs/run_common.sh | 60 +++ .../bpf/prog_tests/bloom_filter_map.c | 177 ++++++++ .../selftests/bpf/progs/bloom_filter_map.c | 157 +++++++ 22 files changed, 1142 insertions(+), 48 deletions(-) create mode 100644 kernel/bpf/bloom_filter.c create mode 100644 tools/testing/selftests/bpf/benchs/bench_bloom_filter_map.c create mode 100755 tools/testing/selftests/bpf/benchs/run_bench_bloom_filter_map.sh create mode 100644 tools/testing/selftests/bpf/benchs/run_common.sh create mode 100644 tools/testing/selftests/bpf/prog_tests/bloom_filter_map.c create mode 100644 tools/testing/selftests/bpf/progs/bloom_filter_map.c -- 2.30.2
