On Wed, Jul 5, 2023 at 9:00 AM Anton Protopopov <aspsk@xxxxxxxxxxxxx> wrote:
>
> Initialize and utilize the per-cpu insertions/deletions counters for hash-based
> maps. Non-trivial changes apply to preallocated maps for which the
> {inc,dec}_elem_count functions are not called, as there's no need in counting
> elements to sustain proper map operations.
>
> To increase/decrease percpu counters for preallocated hash maps we add raw
> calls to the bpf_map_{inc,dec}_elem_count functions so that the impact is
> minimal. For dynamically allocated maps we add corresponding calls to the
> existing {inc,dec}_elem_count functions.
>
> For LRU maps bpf_map_{inc,dec}_elem_count added to the lru pop/free helpers.
>
> Signed-off-by: Anton Protopopov <aspsk@xxxxxxxxxxxxx>
> ---
> kernel/bpf/hashtab.c | 23 +++++++++++++++++++++--
> 1 file changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
> index 56d3da7d0bc6..c23557bf9a1a 100644
> --- a/kernel/bpf/hashtab.c
> +++ b/kernel/bpf/hashtab.c
> @@ -302,6 +302,7 @@ static struct htab_elem *prealloc_lru_pop(struct bpf_htab *htab, void *key,
> struct htab_elem *l;
>
> if (node) {
> + bpf_map_inc_elem_count(&htab->map);
> l = container_of(node, struct htab_elem, lru_node);
> memcpy(l->key, key, htab->map.key_size);
> return l;
> @@ -581,10 +582,17 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
> }
> }
>
> + err = bpf_map_init_elem_count(&htab->map);
> + if (err)
> + goto free_extra_elements;
> +
> return &htab->map;
>
> +free_extra_elements:
> + free_percpu(htab->extra_elems);
> free_prealloc:
> - prealloc_destroy(htab);
> + if (prealloc)
> + prealloc_destroy(htab);
This is a bit difficult to read.
I think the logic would be easier to understand if bpf_map_init_elem_count
was done right before htab->buckets = bpf_map_area_alloc()
and if (err) goto free_htab
where you would add bpf_map_free_elem_count.
