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

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Message-ID: <20191127184400.GA4063@kernel.org>
Date:   Wed, 27 Nov 2019 15:44:00 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Jiri Olsa <jolsa@...nel.org>, lkml <linux-kernel@...r.kernel.org>,
        Network Development <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>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        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

Em Wed, Nov 27, 2019 at 08:37:59AM -0800, Alexei Starovoitov escreveu:
> On Wed, Nov 27, 2019 at 1:48 AM Jiri Olsa <jolsa@...nel.org> wrote:
> > 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

> > which will detect libbpf devel package with needed version,
> > and if found, link it with bpftool.

> > It's possible to use arbitrary installed libbpf:
> >   $ make -C tools/bpf/bpftool/ LIBBPF_DYNAMIC=1 LIBBPF_DIR=/tmp/libbpf/

> > I based this change on top of Arnaldo's perf/core, because
> > it contains libbpf feature detection code as dependency.
> > It's now also synced with latest bpf-next, so Toke's change
> > applies correctly.
 
> I don't like it.
> Especially Toke's patch to expose netlink as public and stable libbpf api.
> bpftools needs to stay tightly coupled with libbpf (and statically
> linked for that reason).
> Otherwise libbpf will grow a ton of public api that would have to be stable
> and will quickly become a burden.

I can relate to that, tools/lib/perf/ is only now getting put in place
because of these fears, hopefully the evsel/evlist/cpumap/etc
abstractions there have been in use for a long time and will be not be a
burden... :-)

- Arnaldo