linux-kernel - Re: [PATCH 0/3] perf/bpftool: Allow to link libbpf dynamically

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Message-ID: <87zhgappl7.fsf@toke.dk>
Date:   Mon, 02 Dec 2019 19:08:52 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Jiri Olsa <jolsa@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Michael Petlan <mpetlan@...hat.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>
Subject: Re: [PATCH 0/3] perf/bpftool: Allow to link libbpf dynamically

Andrii Nakryiko <andrii.nakryiko@...il.com> writes:

> On Wed, Nov 27, 2019 at 1:49 AM Jiri Olsa <jolsa@...nel.org> wrote:
>>
>> hi,
>> adding support to link bpftool with libbpf dynamically,
>> and config change for perf.
>>
>> It's now possible to use:
>>   $ make -C tools/bpf/bpftool/ LIBBPF_DYNAMIC=1
>
> I wonder what's the motivation behind these changes, though? Why is
> linking bpftool dynamically with libbpf is necessary and important?
> They are both developed tightly within kernel repo, so I fail to see
> what are the huge advantages one can get from linking them
> dynamically.

Well, all the regular reasons for using dynamic linking (memory usage,
binary size, etc). But in particular, the ability to update the libbpf
package if there's a serious bug, and have that be picked up by all
utilities making use of it. No reason why bpftool should be special in
that respect.

-Toke