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

Masami Hiramatsu
2016-08-25T06:38:08Z

On Wed, 24 Aug 2016 09:58:45 -0300
Arnaldo Carvalho de Melo <acme@kernel.org> wrote:

> 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:

OK, I'll add it.

>
> [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
> #

Yeah, it looks good especially we don't have to think about --del or
--list with that...

>
> 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
>
> :-)
>

Yeah, it also makes use perf-probe in shell script easier.

> 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.

OK, I couldn't get better name. --definition or -D will be good.

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

Ah, I see :)

>
> --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.

Thanks!

>
> - 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;
> > error:

--
Masami Hiramatsu <mhiramat@kernel.org>