On 25/01/06 05:19PM, Daniel Borkmann wrote: > On 1/6/25 3:53 PM, Charalampos Stylianopoulos wrote: > > This patch series provides an easy way for userspace applications to > > query the number of entries currently present in a map. > > > > Currently, the number of entries in a map is accessible only from kernel space > > and eBPF programs. A userspace program that wants to track map utilization has to > > create and attach an eBPF program solely for that purpose. > > > > This series makes the number of entries in a map easily accessible, by extending the > > main bpf syscall with a new command. The command supports only maps that already > > track utilization, namely hash maps, LPM maps and queue/stack maps. > > An earlier attempt to directly expose it to user space can be found here [0], which > eventually led to [1] to only expose it via kfunc for BPF programs in order to avoid > extending UAPI. > > Perhaps instead add a small libbpf helper (e.g. bpf_map__current_entries to complement > bpf_map__max_entries) which does all the work to extract that info via [1] underneath? One small thingy here is that bpf_map_sum_elem_count() is only available from the map iterator. Which means that to get the bpf_map_sum_elem_count() for one map only, one have to iterate through the whole set of maps (and filter out all but one). I wanted to follow up my series by either adding the result of calling bpf_map_sum_elem_count() to map_info as u32 or to add possibility to provide a map_fd/map_id when creating an iterator (so that it is only called for one map). But so far I haven't a real use case for getting the number of elements for one map only. > Thanks, > Daniel > > [0] https://lore.kernel.org/bpf/20230531110511.64612-1-aspsk@xxxxxxxxxxxxx/ > [1] https://lore.kernel.org/bpf/20230705160139.19967-1-aspsk@xxxxxxxxxxxxx/ > https://lore.kernel.org/bpf/20230719092952.41202-1-aspsk@xxxxxxxxxxxxx/ > > > Charalampos Stylianopoulos (4): > > bpf: Add map_num_entries map op > > bpf: Add bpf command to get number of map entries > > libbpf: Add support for MAP_GET_NUM_ENTRIES command > > selftests/bpf: Add tests for bpf_map_get_num_entries > > > > include/linux/bpf.h | 3 ++ > > include/linux/bpf_local_storage.h | 1 + > > include/uapi/linux/bpf.h | 17 +++++++++ > > kernel/bpf/devmap.c | 14 ++++++++ > > kernel/bpf/hashtab.c | 10 ++++++ > > kernel/bpf/lpm_trie.c | 8 +++++ > > kernel/bpf/queue_stack_maps.c | 11 +++++- > > kernel/bpf/syscall.c | 32 +++++++++++++++++ > > tools/include/uapi/linux/bpf.h | 17 +++++++++ > > tools/lib/bpf/bpf.c | 16 +++++++++ > > tools/lib/bpf/bpf.h | 2 ++ > > tools/lib/bpf/libbpf.map | 1 + > > .../bpf/map_tests/lpm_trie_map_basic_ops.c | 5 +++ > > tools/testing/selftests/bpf/test_maps.c | 35 +++++++++++++++++++ > > 14 files changed, 171 insertions(+), 1 deletion(-) > > >
