On Fri, Feb 9, 2024 at 11:06 PM Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx> wrote: > > On Fri, 9 Feb 2024 at 05:07, Alexei Starovoitov > <alexei.starovoitov@xxxxxxxxx> wrote: > > > > From: Alexei Starovoitov <ast@xxxxxxxxxx> > > > > Convert simple page_frag allocator to per-cpu page_frag to further stress test > > a combination of __arena global and static variables and alloc/free from arena. > > > > Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> > > --- > > I know this organically grew from a toy implementation, but since > people will most likely be looking at selftests as usage examples, it > might be better to expose bpf_preempt_disable/enable and use it in the > case of per-CPU page_frag allocator? No need to block on this, can be > added on top later. > > The kfunc is useful on its own for writing safe per-CPU data > structures or other memory allocators like bpf_ma on top of arenas. > It is also necessary as a building block for writing spin locks > natively in BPF on top of the arena map which we may add later. > I have a patch lying around for this, verifier plumbing is mostly the > same as rcu_read_lock. > I can send it out with tests, or otherwise if you want to add it to > this series, you go ahead. Please send it. I think the verifier checks need to be more tight than rcu_read_lock. preempt_enable/disable should be as strict as bpf_spin_lock. The plan is to add bpf_arena_spin_lock() in the follow up and use it in this bpf page_frag allocator to make it work properly out of tracing context. I'm not sure yet whether bpf_preemp_disable() will be sufficient. And in the long run the idea is to convert all these bpf_arena* facilities into libc equivalent. Probably not part of libbpf, but some new package. name tbd.
