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.