Re: perf/tracepoints access to interpreted strings

From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: David Ahern <dsahern@gmail.com>,
	Namhyung Kim <namhyung@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: perf/tracepoints access to interpreted strings
Date: Mon, 20 Apr 2015 18:25:35 -0300	[thread overview]
Message-ID: <20150420212535.GS11111@kernel.org> (raw)
In-Reply-To: <20150420164616.4227fae9@gandalf.local.home>

Em Mon, Apr 20, 2015 at 04:46:16PM -0400, Steven Rostedt escreveu:
> On Wed, 15 Apr 2015 15:09:27 -0300
> Arnaldo Carvalho de Melo <acme@kernel.org> wrote:
> > If it is strictly an enum, i.e. no holes and just by looking at the
> > "format" file above I don't see how it could have holes, albeit enums
> > may have, we can as well have this:

> > 	const char *perf_evsel__enum(struct perf_evsel *evsel,
> > 				     struct perf_sample *sample,
> > 				     const char *enum_name);

> > That would return an array of strings that you could directly access,
> > indexing using some of the fields.

> > I.e. internally we would see the tracepoint format file as:

> >  	field:enum action vec;	offset:12;	size:4;	signed:0;

> > 	enum: action: TIMER, NET_TX, NET_RX, BLOCK, BLOCK_IOPOLL, TASKLET, SCHED, HRTIMER, RCU

> Note, with the new TRACE_DEFINE_ENUM() that was already added to
> Linus's tree, that print_fmt now looks like:
 
> print fmt: "vec=%u [action=%s]", REC->vec, __print_symbolic(REC->vec,
>  { 0, "HI" }, { 1, "TIMER" }, { 2, "NET_TX" }, { 3, "NET_RX" }, { 4, "BLOCK" },
>  { 5, "BLOCK_IOPOLL" }, { 6, "TASKLET" }, { 7, "SCHED" }, { 8, "HRTIMER" },
>  { 9, "RCU" })

That is better, indeed, covers holes :-)

- Arnaldo