Re: [RFC v2 PATCH bpf-next 1/4] bpf: add percpu stats for bpf_map elements insertions/deletions

Daniel Borkmann
2023-06-23T10:51:36Z

On 6/22/23 11:53 AM, Anton Protopopov wrote:
> Add a generic percpu stats for bpf_map elements insertions/deletions in order
> to keep track of both, the current (approximate) number of elements in a map
> and per-cpu statistics on update/delete operations.
>
> To expose these stats a particular map implementation should initialize the
> counter and adjust it as needed using the 'bpf_map_*_elements_counter' helpers
> provided by this commit. The counter can be read by an iterator program.
>
> A bpf_map_sum_elements_counter kfunc was added to simplify getting the sum of
> the per-cpu values. If a map doesn't implement the counter, then it will always
> return 0.
>
> Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
> ---
> include/linux/bpf.h | 30 +++++++++++++++++++++++++++
> kernel/bpf/map_iter.c | 48 ++++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 77 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index f58895830ada..20292a096188 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -275,6 +275,7 @@ struct bpf_map {
> } owner;
> bool bypass_spec_v1;
> bool frozen; /* write-once; write-protected by freeze_mutex */
> + s64 __percpu *elements_count;

To avoid corruption on 32 bit archs, should we convert this into local64_t here?