Re: [BPF PATCH for-next] cgroup/bpf: fast path for not loaded skb BPF filtering

[Pavel Begunkov]

On 12/14/21 17:54, sdf@xxxxxxxxxx wrote:
> On 12/11, Pavel Begunkov wrote:
> > On 12/11/21 01:56, Martin KaFai Lau wrote:
> > > On Sat, Dec 11, 2021 at 01:15:05AM +0000, Pavel Begunkov wrote:
> > > > That was the first idea, but it's still heavier than I'd wish. 0.3%-0.7%
> > > > in profiles, something similar in reqs/s. rcu_read_lock/unlock() pair is
> > > > cheap but anyway adds 2 barrier()s, and with bitmasks we can inline
> > > > the check.
> > > It sounds like there is opportunity to optimize
> > > __cgroup_bpf_prog_array_is_empty().
> > >
> > > How about using rcu_access_pointer(), testing with &empty_prog_array.hdr,
> > > and then inline it?  The cgroup prog array cannot be all
> > > dummy_bpf_prog.prog.  If that could be the case, it should be replaced
> > > with &empty_prog_array.hdr earlier, so please check.
>
> > I'd need to expose and export empty_prog_array, but that should do.
> > Will try it out, thanks
>
> Note that we already use __cgroup_bpf_prog_array_is_empty in
> __cgroup_bpf_run_filter_setsockopt/__cgroup_bpf_run_filter_getsockopt
> for exactly the same purpose. If you happen to optimize it, pls
> update these places as well.

Just like it's already done in the patch? Or maybe you mean something else?

--
Pavel Begunkov