Re: [PATCH bpf-next 17/18] bpf: add bpf_wq_start

[Benjamin Tissoires]

On Apr 19 2024, Alexei Starovoitov wrote:
> On Fri, Apr 19, 2024 at 8:14 AM Benjamin Tissoires <bentiss@xxxxxxxxxx> wrote:
> >
> >
> > Honestly I just felt the patch series was big enough for a PoC and
> > comparison with sleepable bpf_timer. But if we think this needs not to
> > be added, I guess that works too :)
> 
> It certainly did its job to compare the two and imo bpf_wq with kfunc approach
> looks cleaner overall and will be easier to extend in the long term.

Yeah. I agree. I'm also glad we pick the bpf_wq approach as I gave it a
lot more care :)

Talking about extending, I think I'll need delayed_work soon enough.
Most of the time when I receive an input event, the device is preventing
any communication with it, and with plain bpf_wq, it's likely that when
the code kicks in the device won't have processed the current input,
meaning to a useless retry. With delayed_works, I can schedule it
slightly later, and have a higher chance of not having to retry.

I've got a quick hack locally that I can submit once this series get
merged.

> 
> I mean that we'll be adding 3 kfuncs initially:
> bpf_wq_init, bpf_wq_start, bpf_wq_set_callback.
> 
> imo that's good enough to land it and get some exposure.

sounds good to me.

> I'll be using it right away to refactor bpf_arena_alloc.h into
> actual arena allocator for bpf progs that is not just a selftest.
> 
> I'm currently working on locks for bpf_arena.
> Kumar has a patch set that adds bpf_preempt_disble kfunc and
> coupled with bpf_wq we'll have all mechanisms to build
> arbitrary data structures/algorithms as bpf programs.

Oh. I did not realize that it was that needed for outside of my
playground. That's good to hear :)

Cheers,
Benjamin