Re: [PATCH v8 02/18] perf ftrace: add option '-F/--funcs' to list available functions

From: Changbin Du <changbin.du@gmail.com>
To: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Cc: Changbin Du <changbin.du@gmail.com>, Jiri Olsa <jolsa@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v8 02/18] perf ftrace: add option '-F/--funcs' to list available functions
Date: Thu, 20 Aug 2020 23:18:25 +0800	[thread overview]
Message-ID: <20200820151825.idfidxxbat6e32ur@mail.google.com> (raw)
In-Reply-To: <20200814113535.GS13995@kernel.org>

On Fri, Aug 14, 2020 at 08:35:35AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Sat, Aug 08, 2020 at 10:31:25AM +0800, Changbin Du escreveu:
> > This adds an option '-F/--funcs' to list all available functions to trace,
> > which is read from tracing file 'available_filter_functions'.
> > 
> > $ sudo ./perf ftrace -F | head
> > trace_initcall_finish_cb
> > initcall_blacklisted
> > do_one_initcall
> > do_one_initcall
> > trace_initcall_start_cb
> > run_init_process
> > try_to_run_init_process
> > match_dev_by_label
> > match_dev_by_uuid
> > rootfs_init_fs_context
> > 
> > Signed-off-by: Changbin Du <changbin.du@gmail.com>
> > 
> > ---
> > v3: fix return value issue.
> > v2: option name '-l/--list-functions' -> '-F/--funcs'
> > ---
> >  tools/perf/Documentation/perf-ftrace.txt |  4 +++
> >  tools/perf/builtin-ftrace.c              | 46 ++++++++++++++++++++++++
> >  2 files changed, 50 insertions(+)
> > 
> > diff --git a/tools/perf/Documentation/perf-ftrace.txt b/tools/perf/Documentation/perf-ftrace.txt
> > index 821d4d334a09..4f5628445a63 100644
> > --- a/tools/perf/Documentation/perf-ftrace.txt
> > +++ b/tools/perf/Documentation/perf-ftrace.txt
> > @@ -31,6 +31,10 @@ OPTIONS
> >  --verbose=::
> >          Verbosity level.
> >  
> > +-F::
> > +--funcs::
> > +        List all available functions to trace.
> > +
> >  -p::
> >  --pid=::
> >  	Trace on existing process id (comma separated list).
> > diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> > index 048a11192b59..1ebf71ecc1a8 100644
> > --- a/tools/perf/builtin-ftrace.c
> > +++ b/tools/perf/builtin-ftrace.c
> > @@ -33,6 +33,7 @@ struct perf_ftrace {
> >  	struct evlist		*evlist;
> >  	struct target		target;
> >  	const char		*tracer;
> > +	bool			list_avail_functions;
> >  	struct list_head	filters;
> >  	struct list_head	notrace;
> >  	struct list_head	graph_funcs;
> > @@ -128,6 +129,46 @@ static int append_tracing_file(const char *name, const char *val)
> >  	return __write_tracing_file(name, val, true);
> >  }
> >  
> > +static int read_tracing_file_to_stdout(const char *name)
> > +{
> > +	char buf[4096];
> > +	char *file;
> > +	int fd;
> > +	int ret = -1;
> > +
> > +	file = get_tracing_file(name);
> > +	if (!file) {
> > +		pr_debug("cannot get tracing file: %s\n", name);
> > +		return -1;
> > +	}
> > +
> > +	fd = open(file, O_RDONLY);
> > +	if (fd < 0) {
> > +		pr_debug("cannot open tracing file: %s: %s\n",
> > +			 name, str_error_r(errno, buf, sizeof(buf)));
> > +		goto out;
> > +	}
> > +
> > +	/* read contents to stdout */
> > +	while (true) {
> > +		int n = read(fd, buf, sizeof(buf));
> > +		if (n == 0)
> > +			break;
> > +		else if (n < 0)
> > +			goto out_close;
> > +
> > +		if (fwrite(buf, n, 1, stdout) != 1)
> > +			goto out_close;
> > +	}
> > +	ret = 0;
> > +
> > +out_close:
> > +	close(fd);
> > +out:
> > +	put_tracing_file(file);
> > +	return ret;
> > +}
> > +
> >  static int reset_tracing_cpu(void);
> >  static void reset_tracing_filters(void);
> >  
> > @@ -302,6 +343,9 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
> >  	signal(SIGCHLD, sig_handler);
> >  	signal(SIGPIPE, sig_handler);
> >  
> > +	if (ftrace->list_avail_functions)
> > +		return read_tracing_file_to_stdout("available_filter_functions");
> > +
> >  	if (reset_tracing_files(ftrace) < 0) {
> >  		pr_err("failed to reset ftrace\n");
> >  		goto out;
> > @@ -487,6 +531,8 @@ int cmd_ftrace(int argc, const char **argv)
> >  	const struct option ftrace_options[] = {
> >  	OPT_STRING('t', "tracer", &ftrace.tracer, "tracer",
> >  		   "tracer to use: function_graph(default) or function"),
> > +	OPT_BOOLEAN('F', "funcs", &ftrace.list_avail_functions,
> > +		    "Show available functions to filter"),
> 
> A boolean? I guess this can be a first step, but why not do it like
> 'perf probe' and accept a patterna? Allows for less typing:
> 
>   # perf probe -h -F
> 
>     -F, --funcs <[FILTER]>
>                           Show potential probe-able functions.
> 
> [root@quaco ~]#
> 
> # perf probe -F '*btf_parse*'
> btf_parse_hdr
> btf_parse_str_sec
> btf_parse_vmlinux
> #
> # perf ftrace -F | grep btf_parse
> btf_parse_str_sec
> btf_parse_hdr
> btf_parse_vmlinux
> #
> 
> I'm applying this to make progress, but please consider sending a patch
> to make this behave in the same way as 'perf probe'.
>
No problem, I'll try to provide similar behaviour for this. Thanks.

> - Arnaldo
> 
> 
> >  	OPT_STRING('p', "pid", &ftrace.target.pid, "pid",
> >  		   "trace on existing process id"),
> >  	OPT_INCR('v', "verbose", &verbose,
> > -- 
> > 2.25.1
> > 
> 
> -- 
> 
> - Arnaldo

-- 
Cheers,
Changbin Du