linux-kernel - Re: [RFC PATCH perf/core v2 00/16] perf-probe --cache and SDT support

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Date:	Tue, 28 Jul 2015 10:45:21 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Namhyung Kim <namhyung@...nel.org>,
	Hemant Kumar <hemant@...ux.vnet.ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org,
	Adrian Hunter <adrian.hunter@...el.com>,
	Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...nel.org>,
	Borislav Petkov <bp@...e.de>
Subject: Re: [RFC PATCH perf/core v2 00/16] perf-probe --cache and SDT support

Em Tue, Jul 28, 2015 at 09:42:59AM +0900, Masami Hiramatsu escreveu:
> On 2015/07/28 0:16, Arnaldo Carvalho de Melo wrote:
> > Em Mon, Jul 27, 2015 at 11:03:20PM +0900, Namhyung Kim escreveu:
> >> IMHO @ looks perfect for pathnames but I don't know about build-id as
> >> it can be thought as some address.  Anyway I still think @ is a good
> >> choice though. ;-)

> > Yeah, perhaps we need further clarification? I.e. something like:

> > 	sdt_foo:bar:libfoo1.so@...ldid(0x1234)

> > Or something else, perhaps shorter, that clarifies that it is a buildid?
> 
> Hmm, Do we really need such additional buildid? Even though, I think

"or something else, perhaps shorter" :-)

> the build id should have different delimiter, like '%', as below.
> 
> sdt_foo:bar@...foo1.so%buildid

How about:

	sdt_foo:bar@...foo1.so(0x1234)

Which is clear, to humans: "hey, I want the SDT event 'bar' at the
'libfoo1' library, but make sure it is the one which contents have build
id '0x1234'".

But even the name of the library is not strictly needed, would be just a
nicety for humans, as the way buildids are looked up are by means of:

[acme@zoo tuna]$ ls -la /usr/lib/debug/.build-id/ | tail -5
drwxr-xr-x.   2 root root 4096 Jul 23 09:26 fb/
drwxr-xr-x.   2 root root 4096 Jun 22 19:35 fc/
drwxr-xr-x.   2 root root 4096 Jun 22 19:35 fd/
drwxr-xr-x.   2 root root 4096 Jun 22 19:35 fe/
drwxr-xr-x.   2 root root 4096 Jun 26 16:57 ff/
[acme@zoo tuna]$

So, having:

	sdt_foo:bar@...234

Should be unambiguous and shorter.

- ARnaldo
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