This introduces a new command to retrieve a variable number of entries from a bpf map. This new command can be executed from the existing BPF syscall as follows: err = bpf(BPF_MAP_DUMP, union bpf_attr *attr, u32 size) using attr->dump.map_fd, attr->dump.prev_key, attr->dump.buf, attr->dump.buf_len returns zero or negative error, and populates buf and buf_len on succees This implementation is wrapping the existing bpf methods: map_get_next_key and map_lookup_elem the results show that even with a 1-elem_size buffer, it runs ~40 faster than the current implementation, improvements of ~85% are reported when the buffer size is increased, although, after the buffer size is around 5% of the total number of entries there's no huge difference in increasing it. Tested: Tried different size buffers to handle case where the bulk is bigger, or the elements to retrieve are less than the existing ones, all runs read a map of 100K entries. Below are the results(in ns) from the different runs: buf_len_1: 69038725 entry-by-entry: 112384424 improvement 38.569134 buf_len_2: 40897447 entry-by-entry: 111030546 improvement 63.165590 buf_len_230: 13652714 entry-by-entry: 111694058 improvement 87.776687 buf_len_5000: 13576271 entry-by-entry: 111101169 improvement 87.780263 buf_len_73000: 14694343 entry-by-entry: 111740162 improvement 86.849542 buf_len_100000: 13745969 entry-by-entry: 114151991 improvement 87.958187 buf_len_234567: 14329834 entry-by-entry: 114427589 improvement 87.476941 Changelog: v3: - add explanation of the API in the commit message - fix masked errors and return them to user - copy last_key from return buf into prev_key if it was provided - run test with kpti and retpoline mitigations v2: - use proper bpf-next tag Brian Vazquez (6): bpf: add bpf_map_value_size and bp_map_copy_value helper functions bpf: add BPF_MAP_DUMP command to dump more than one entry per call bpf: keep bpf.h in sync with tools/ libbpf: support BPF_MAP_DUMP command selftests/bpf: test BPF_MAP_DUMP command on a bpf hashmap selftests/bpf: add test to measure performance of BPF_MAP_DUMP include/uapi/linux/bpf.h | 9 + kernel/bpf/syscall.c | 252 ++++++++++++++++++------ tools/include/uapi/linux/bpf.h | 9 + tools/lib/bpf/bpf.c | 28 +++ tools/lib/bpf/bpf.h | 4 + tools/lib/bpf/libbpf.map | 2 + tools/testing/selftests/bpf/test_maps.c | 147 +++++++++++++- 7 files changed, 388 insertions(+), 63 deletions(-) -- 2.22.0.410.gd8fdbe21b5-goog
