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Date:   Wed, 11 Mar 2020 17:13:20 +0100
From:   Jiri Olsa <jolsa@redhat.com>
To:     Stephane Eranian <eranian@google.com>
Cc:     Andi Kleen <ak@linux.intel.com>, Ian Rogers <irogers@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin KaFai Lau <kafai@fb.com>, Yonghong Song <yhs@fb.com>,
        Andrii Nakryiko <andriin@fb.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Igor Lubashev <ilubashe@akamai.com>,
        Alexey Budankov <alexey.budankov@linux.intel.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Jiwei Sun <jiwei.sun@windriver.com>,
        yuzhoujian <yuzhoujian@didichuxing.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        Jin Yao <yao.jin@linux.intel.com>,
        Leo Yan <leo.yan@linaro.org>,
        John Garry <john.garry@huawei.com>,
        LKML <linux-kernel@vger.kernel.org>, netdev@vger.kernel.org,
        bpf@vger.kernel.org, linux-perf-users@vger.kernel.org
Subject: Re: [PATCH] perf tools: add support for lipfm4
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On Tue, Mar 10, 2020 at 02:39:23PM -0700, Stephane Eranian wrote:
> On Tue, Mar 10, 2020 at 12:59 PM Andi Kleen <ak@linux.intel.com> wrote:
> >
> > On Tue, Mar 10, 2020 at 11:50:03AM -0700, Ian Rogers wrote:
> > > This patch links perf with the libpfm4 library.
> > > This library contains all the hardware event tables for all
> > > processors supported by perf_events. This is a helper library
> > > that help convert from a symbolic event name to the event
> > > encoding required by the underlying kernel interface. This
> > > library is open-source and available from: http://perfmon2.sf.net.
> >
> > For most CPUs the builtin perf JSON event support should make
> > this redundant.
> >
> We decided to post this patch to propose an alternative to the JSON
> file approach. It could be an option during the build.
> The libpfm4 library has been around for 15 years now. Therefore, it
> supports a lot of processors core and uncore and it  is very portable.
> The key value add I see is that this is a library that can be, and has
> been, used by tool developers directly in their apps. It can
> work with more than Linux perf_events interface. It is not tied to the
> interface. It has well defined and documented entry points.
> We do use libpfm4 extensively at Google in both the perf tool and
> applications. The PAPI toolkit also relies on this library.
> 
> I don't see this as competing with the JSON approach. It is just an
> option I'd like to offer to users especially those familiar
> with it in their apps.

I dont mind having it, in fact I found really old email where I'm
asking Peter about that ;-) and he wasn't very keen about that:
  https://lore.kernel.org/lkml/1312806326.10488.30.camel@twins/

not sure what was the actual reason at that time and if anything
changed since.. Peter?

btw I can't apply even that v2 on latest Arnaldo's branch

jirka