Re: [RFC PATCH 2/4] perf-probe: Add offline output directory option

Arnaldo Carvalho de Melo
2016-08-24T12:58:58Z

Em Wed, Aug 24, 2016 at 02:58:12PM +0900, Masami Hiramatsu escreveu:
> Add offline output direcrtory option. This allows user to
> store probe event definition in offline output directory.

In such cases you should show it in action, like I am doing now to test
this patch:

[root@jouet ~]# perf probe --outdir=my_probes do_open
kprobe_events file does not exist - please rebuild kernel with CONFIG_KPROBE_EVENTS.
Error: Failed to add events.
[root@jouet ~]#

Oops, misleading error message, probably I need to first do a mkdir:

[root@jouet ~]# mkdir my_probes
[root@jouet ~]# perf probe --outdir=my_probes do_open
Added new event:
probe:do_open (on do_open)

You can now use it in all perf tools, such as:

perf record -e probe:do_open -aR sleep 1

[root@jouet ~]# ls -la my_probes
total 12
drwxr-xr-x. 2 root root 4096 Aug 24 09:47 .
dr-xr-x---. 31 root root 4096 Aug 24 09:47 ..
-rw-r--r--. 1 root root 30 Aug 24 09:47 kprobe_events
[root@jouet ~]# cat my_probes/kprobe_events
p:probe/do_open _text+3481584
[root@jouet ~]#

Wouldn't it be better to call it some other name and imply --dry-run? "outdir"
seems too vague. Perhaps --definition and instead have it run like:

# perf probe --definition do_open
p:probe/do_open _text+3481584
#

Then one could even use it to redirect it to a file, tee + file and even test it as:

# perf probe --definition do_open > /sys/kernel/debug/tracing/kprobe_events
#

For debugging:

# perf probe --definition do_open | tee /sys/kernel/debug/tracing/kprobe_events

:-)

I picked "--kprobes" first, but that would left out e.g. uprobes, then I
thought about --event, but also sounds vague, read
Documentation/trace/kprobetrace.txt and saw this bit:

-------
Usage examples
--------------
To add a probe as a new event, write a new definition to kprobe_events
as below.

echo 'p:myprobe do_sys_open dfd=%ax filename=%dx flags=%cx mode=+4($stack)' > /sys/kernel/debug/tracing/kprobe_events
-------

So you used "definition" for that string, might as well be consistent and use
it here as well.

Also please fix the OPT_STRING string, it should start with a capital
letter:

--max-probes <n> Set how many probe points can be found for a probe.
--no-inlines Don't search inlined functions
--outdir <directory>
path to offline output directory
--range Show variables location range in scope (with --vars only)

See how it stands out? All the others start with a capital letter.

I applied the first patch, totally trivial.

- Arnaldo

> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> ---
> tools/perf/builtin-probe.c | 2 ++
> tools/perf/util/probe-event.h | 1 +
> tools/perf/util/probe-file.c | 19 ++++++++++++++++---
> 3 files changed, 19 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/builtin-probe.c b/tools/perf/builtin-probe.c
> index ee5b421..5b45ec8 100644
> --- a/tools/perf/builtin-probe.c
> +++ b/tools/perf/builtin-probe.c
> @@ -517,6 +517,8 @@ __cmd_probe(int argc, const char **argv, const char *prefix __maybe_unused)
> "Show variables location range in scope (with --vars only)"),
> OPT_STRING('k', "vmlinux", &symbol_conf.vmlinux_name,
> "file", "vmlinux pathname"),
> + OPT_STRING(0, "outdir", &probe_conf.output_dir,
> + "directory", "path to offline output directory"),
> OPT_STRING('s', "source", &symbol_conf.source_prefix,
> "directory", "path to kernel source"),
> OPT_BOOLEAN('\0', "no-inlines", &probe_conf.no_inlines,
> diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
> index f4f45db..75b572a 100644
> --- a/tools/perf/util/probe-event.h
> +++ b/tools/perf/util/probe-event.h
> @@ -14,6 +14,7 @@ struct probe_conf {
> bool no_inlines;
> bool cache;
> int max_probes;
> + const char *output_dir;
> };
> extern struct probe_conf probe_conf;
> extern bool probe_event_dry_run;
> diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
> index 6f931e4..41db430 100644
> --- a/tools/perf/util/probe-file.c
> +++ b/tools/perf/util/probe-file.c
> @@ -73,16 +73,25 @@ static void print_both_open_warning(int kerr, int uerr)
> static int open_probe_events(const char *trace_file, bool readwrite)
> {
> char buf[PATH_MAX];
> + const char *tracing_dir = tracing_path;
> + int oflag = 0;
> + mode_t mode = 0;
> int ret;
>
> + if (probe_conf.output_dir) {
> + tracing_dir = probe_conf.output_dir;
> + oflag = O_CREAT;
> + mode = 0644;
> + }
> +
> ret = e_snprintf(buf, PATH_MAX, "%s/%s",
> - tracing_path, trace_file);
> + tracing_dir, trace_file);
> if (ret >= 0) {
> pr_debug("Opening %s write=%d\n", buf, readwrite);
> if (readwrite && !probe_event_dry_run)
> - ret = open(buf, O_RDWR | O_APPEND, 0);
> + ret = open(buf, O_RDWR | O_APPEND | oflag, mode);
> else
> - ret = open(buf, O_RDONLY, 0);
> + ret = open(buf, O_RDONLY | oflag, mode);
>
> if (ret < 0)
> ret = -errno;
> @@ -242,6 +251,8 @@ int probe_file__add_event(int fd, struct probe_trace_event *tev)
> pr_warning("Failed to write event: %s\n",
> str_error_r(errno, sbuf, sizeof(sbuf)));
> }
> + if (probe_conf.output_dir)
> + ret = write(fd, "\n", 1) == 1 ? 0 : -errno;
> }
> free(buf);
>
> @@ -274,6 +285,8 @@ static int __del_trace_probe_event(int fd, struct str_node *ent)
> ret = -errno;
> goto error;
> }
> + if (probe_conf.output_dir)
> + ret = write(fd, "\n", 1) == 1 ? 0 : -errno;
>
> return 0;