by Arnaldo Carvalho de Melo

[permalink] [raw]

Subject: Re: [PATCH v6 02/17] perf ftrace: add option '-F/--funcs' to list available functions

Em Fri, Jul 17, 2020 at 10:36:13PM +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'.

I'll apply and add a comment stating that this is the same workflow as
for 'perf probe', i.e. stress that the value in 'perf ftrace' as opposed
to use 'trace-cmd' or plain using the debugfs/tracefs interface is to
have a consistent set of options and procedures accross perf and ftrace,
one that allows users to go from:

perf trace --pid 1234

to:

perf ftrace --pid 1234

to:

perf stat --pid 1234

to:

perf top --pid 1234

to:

perf record --pid 1234

to:

perf script --pid 1234

etc

and get different views, for live or postmortem analysis.

- Arnaldo

> $ 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 <[email protected]>
>
> ---
> 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 952e46669168..d79560dea19f 100644
> --- a/tools/perf/Documentation/perf-ftrace.txt
> +++ b/tools/perf/Documentation/perf-ftrace.txt
> @@ -30,6 +30,10 @@ 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 5f53da87040d..3c0e60fdfe0f 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -32,6 +32,7 @@ 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;
> @@ -127,6 +128,46 @@ 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);
>
> @@ -301,6 +342,9 @@ 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;
> @@ -470,6 +514,8 @@ int cmd_ftrace(int argc, const char **argv)
> const struct option ftrace_options[] = {
> OPT_STRING('t', "tracer", &ftrace.tracer, "tracer",
> "tracer to use: function or function_graph (This option is deprecated)"),
> + OPT_BOOLEAN('F', "funcs", &ftrace.list_avail_functions,
> + "Show available functions to filter"),
> OPT_STRING('p', "pid", &ftrace.target.pid, "pid",
> "trace on existing process id"),
> OPT_INCR('v', "verbose", &verbose,
> --
> 2.25.1
>

--

- Arnaldo