linux-kernel - Re: [PATCH bpf-next v2 27/35] bpf: eliminate rlimit-based memory accounting infra for bpf maps

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Date:   Mon, 27 Jul 2020 22:58:39 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Song Liu <song@...nel.org>
Cc:     Roman Gushchin <guro@...com>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next v2 27/35] bpf: eliminate rlimit-based memory
 accounting infra for bpf maps

On Mon, Jul 27, 2020 at 10:47 PM Song Liu <song@...nel.org> wrote:
>
> On Mon, Jul 27, 2020 at 12:26 PM Roman Gushchin <guro@...com> wrote:
> >
> > Remove rlimit-based accounting infrastructure code, which is not used
> > anymore.
> >
> > Signed-off-by: Roman Gushchin <guro@...com>
> [...]
> >
> >  static void bpf_map_put_uref(struct bpf_map *map)
> > @@ -541,7 +484,7 @@ static void bpf_map_show_fdinfo(struct seq_file *m, struct file *filp)
> >                    "value_size:\t%u\n"
> >                    "max_entries:\t%u\n"
> >                    "map_flags:\t%#x\n"
> > -                  "memlock:\t%llu\n"
> > +                  "memlock:\t%llu\n" /* deprecated */
>
> I am not sure whether we can deprecate this one.. How difficult is it
> to keep this statistics?
>

It's factually correct now, that BPF map doesn't use any memlock memory, no?

This is actually one way to detect whether RLIMIT_MEMLOCK is necessary
or not: create a small map, check if it's fdinfo has memlock: 0 or not
:)

> Thanks,
> Song