Re: [PATCH bpf-next v2 29/35] bpf: libbpf: cleanup RLIMIT_MEMLOCK usage

[Roman Gushchin]

On Mon, Jul 27, 2020 at 03:05:11PM -0700, Andrii Nakryiko wrote:
> On Mon, Jul 27, 2020 at 12:21 PM Roman Gushchin <guro@xxxxxx> wrote:
> >
> > As bpf is not using memlock rlimit for memory accounting anymore,
> > let's remove the related code from libbpf.
> >
> > Bpf operations can't fail because of exceeding the limit anymore.
> >
> 
> They can't in the newest kernel, but libbpf will keep working and
> supporting old kernels for a very long time now. So please don't
> remove any of this.

Yeah, good point, agree.
So we just can drop this patch from the series, no other changes
are needed.

> 
> But it would be nice to add a detection of whether kernel needs a
> RLIMIT_MEMLOCK bump or not. Is there some simple and reliable way to
> detect this from user-space?

Hm, the best idea I can think of is to wait for -EPERM before bumping.
We can in theory look for the presence of memory.stat::percpu in cgroupfs,
but it's way to cryptic.

Thanks!