linux-kernel - Re: [RFC PATCH] perf: Provide status of known PMUs

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Message-ID: <20150709144749.GA19430@kernel.org>
Date:	Thu, 9 Jul 2015 11:47:49 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Andy Lutomirski <luto@...capital.net>,
	Vince Weaver <vincent.weaver@...ne.edu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...hat.com>,
	Stephane Eranian <eranian@...gle.com>,
	Borislav Petkov <bp@...e.de>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [RFC PATCH] perf: Provide status of known PMUs

Em Thu, Jul 09, 2015 at 02:42:57PM +0200, Peter Zijlstra escreveu:
> On Thu, Jul 09, 2015 at 02:32:05PM +0200, Ingo Molnar wrote:

> >    perf record error: The 'bts' PMU is not available, because the CPU does not support it
 
> This one makes sense.
 
> >    perf record error: The 'bts' PMU is not available, because this architecture does not support it
> >    perf record error: The 'bts' PMU is not available, because its driver is not built into the kernel

> > Because if it's the wrong architecture or CPU, I look for a box with
> > the right one, if it's simply the kernel not having the necessary
> > PMU driver then I'll boot a kernel with it enabled.
 
> These not so much; why won't a generic: "Unknown PMU, check
> arch/kernel" do?
 
> The thing is, I hate that hard-coded list, its pain I don't need.

Well, then we need to have tooling looking around and having tables to
provide those more precise error messages, which we want to have.

I guess we can do parts of that by looking at info already exported by
the kernel, /proc/cpuinfo stuff, etc. But "Unknown PMU, check
arch/kernel" is way too vague :-\

- Arnaldo
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