Subject: Re: [PATCH] perf tools: add support for lipfm4

From: Jiri Olsa <[email-masked]>
Date: Wed, 11 Mar 2020 17:13:20 +0100

On Tue, Mar 10, 2020 at 02:39:23PM -0700, Stephane Eranian wrote:
> On Tue, Mar 10, 2020 at 12:59 PM Andi Kleen <[email-masked]> 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