On Fri, Dec 10, 2021 at 02:23:34AM +0000, Pavel Begunkov wrote:
> cgroup_bpf_enabled_key static key guards from overhead in cases where
> no cgroup bpf program of a specific type is loaded in any cgroup. Turn
> out that's not always good enough, e.g. when there are many cgroups but
> ones that we're interesting in are without bpf. It's seen in server
> environments, but the problem seems to be even wider as apparently
> systemd loads some BPF affecting my laptop.
>
> Profiles for small packet or zerocopy transmissions over fast network
> show __cgroup_bpf_run_filter_skb() taking 2-3%, 1% of which is from
> migrate_disable/enable(), and similarly on the receiving side. Also
> got +4-5% of t-put for local testing.
>
> Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
> ---
> include/linux/bpf-cgroup.h | 24 +++++++++++++++++++++---
> kernel/bpf/cgroup.c | 23 +++++++----------------
> 2 files changed, 28 insertions(+), 19 deletions(-)
>
> diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
> index 11820a430d6c..99b01201d7db 100644
> --- a/include/linux/bpf-cgroup.h
> +++ b/include/linux/bpf-cgroup.h
> @@ -141,6 +141,9 @@ struct cgroup_bpf {
> struct list_head progs[MAX_CGROUP_BPF_ATTACH_TYPE];
> u32 flags[MAX_CGROUP_BPF_ATTACH_TYPE];
>
> + /* for each type tracks whether effective prog array is not empty */
> + unsigned long enabled_mask;
> +
> /* list of cgroup shared storages */
> struct list_head storages;
>
> @@ -219,11 +222,25 @@ int bpf_percpu_cgroup_storage_copy(struct bpf_map *map, void *key, void *value);
> int bpf_percpu_cgroup_storage_update(struct bpf_map *map, void *key,
> void *value, u64 flags);
>
> +static inline bool __cgroup_bpf_type_enabled(struct cgroup_bpf *cgrp_bpf,
> + enum cgroup_bpf_attach_type atype)
> +{
> + return test_bit(atype, &cgrp_bpf->enabled_mask);
> +}
> +
> +#define CGROUP_BPF_TYPE_ENABLED(sk, atype) \
> +({ \
> + struct cgroup *__cgrp = sock_cgroup_ptr(&(sk)->sk_cgrp_data); \
> + \
> + __cgroup_bpf_type_enabled(&__cgrp->bpf, (atype)); \
> +})
I think it should directly test if the array is empty or not instead of
adding another bit.
Can the existing __cgroup_bpf_prog_array_is_empty(cgrp, ...) test be used instead?
