linux-kernel - Re: [PATCH 2/2] perf stat: Also hide metric from JSON if units are an empty string

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAP-5=fW9fy3PEicYgmhqQFUJmJaFs_LiponqYwEJGc7u7KQcxA@mail.gmail.com>
Date: Wed, 30 Oct 2024 08:38:53 -0700
From: Ian Rogers <irogers@...gle.com>
To: James Clark <james.clark@...aro.org>
Cc: Namhyung Kim <namhyung@...nel.org>, linux-perf-users@...r.kernel.org, acme@...nel.org, 
	tim.c.chen@...ux.intel.com, Peter Zijlstra <peterz@...radead.org>, 
	Ingo Molnar <mingo@...hat.com>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, "Liang, Kan" <kan.liang@...ux.intel.com>, 
	Yicong Yang <yangyicong@...ilicon.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] perf stat: Also hide metric from JSON if units are an
 empty string

On Wed, Oct 30, 2024 at 2:36 AM James Clark <james.clark@...aro.org> wrote:
>
>
>
> On 30/10/2024 2:45 am, Ian Rogers wrote:
> > On Tue, Oct 29, 2024 at 5:42 PM Namhyung Kim <namhyung@...nel.org> wrote:
> >>
> >> Hello,
> >>
> >> On Fri, Oct 25, 2024 at 10:03:05AM +0100, James Clark wrote:
> >>> We decided to hide NULL metric units rather than showing it as "(null)",
> >>> but on hybrid systems if the process doesn't hit a PMU you get an empty
> >>> string metric unit instead. To make it consistent also remove empty
> >>> strings.
> >>>
> >>> Note that metric-threshold is already hidden in this case without this
> >>> change.
> >>>
> >>> Where a process only runs on cpu_core and never hits cpu_atom:
> >>> Before:
> >>>   $ perf stat -j -- true
> >>>   ...
> >>>   {"counter-value" : "<not counted>", "unit" : "", "event" : "cpu_atom/branch-misses/", "event-runtime" : 0, "pcnt-running" : 0.00, "metric-value" : "0.000000", "metric-unit" : ""}
> >>>   {"counter-value" : "6326.000000", "unit" : "", "event" : "cpu_core/branch-misses/", "event-runtime" : 293786, "pcnt-running" : 100.00, "metric-value" : "3.553394", "metric-unit" : "of all branches", "metric-threshold" : "good"}
> >>>   ...
> >>
> >> I guess you're talking about "metric-unit", not plain "unit", right?
> >> Then please update the subject line to reduce the config.
> >>
>
> Yep I'll update it.
>
> >> Ian, can you please review?
> >
> > It'd be nice to see the stack trace for when metric-unit is "" as I'm
> > not seeing the logic in stat-shadow.c. If we know the caller than it
> > seems logical the unit can be passed as NULL rather than "".
> >
> > Thanks,
> > Ian
> >
>
>
> Here's the stack:
>
> print_metric_json() (stat-display.c:516)
> printout() (stat-display.c:912)
> print_counter_aggrdata() (stat-display.c:1110)
> print_counter() (stat-display.c:1224)
> evlist__print_counters() (stat-display.c:1734)
> print_counters() (builtin-stat.c:1016)
> cmd_stat() (builtin-stat.c:2872)
> run_builtin() (perf/perf.c:351)
> handle_internal_command() (perf.c:404)
> run_argv() (perf.c:448)
> main() (perf.c:560)
>
> The empty string is from printout():
>
>    pm(config, os, METRIC_THRESHOLD_UNKNOWN, /*format=*/NULL, /*unit=*/"",
>       /*val=*/0);
>
> Changing it to NULL seems to work, so is probably a bit neater. I can do
> that if you think that makes sense?
>
> There's another one for --metric-only that I didn't run into, but it
> could also make sense to change:
>
>    if (config->metric_only) {
>      pm(config, os, METRIC_THRESHOLD_UNKNOWN, "", "", 0);

Yeah, it looks like all the callers should be passing NULL. I feel
more comfortable doing this than ignoring the empty string which is
something a json metric may accidentally do. Could you send a patch?

Thanks,
Ian

> >> Thanks,
> >> Namhyung
> >>
> >>>
> >>> After:
> >>>   ...
> >>>   {"counter-value" : "<not counted>", "unit" : "", "event" : "cpu_atom/branch-misses/", "event-runtime" : 0, "pcnt-running" : 0.00}
> >>>   {"counter-value" : "5778.000000", "unit" : "", "event" : "cpu_core/branch-misses/", "event-runtime" : 282240, "pcnt-running" : 100.00, "metric-value" : "3.226797", "metric-unit" : "of all branches", "metric-threshold" : "good"}
> >>>   ...
> >>>
> >>> Signed-off-by: James Clark <james.clark@...aro.org>
> >>> ---
> >>>   tools/perf/util/stat-display.c | 2 +-
> >>>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>>
> >>> diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
> >>> index a5d72f4a515c..9b7fd985a42a 100644
> >>> --- a/tools/perf/util/stat-display.c
> >>> +++ b/tools/perf/util/stat-display.c
> >>> @@ -506,7 +506,7 @@ static void print_metric_json(struct perf_stat_config *config __maybe_unused,
> >>>        struct outstate *os = ctx;
> >>>        FILE *out = os->fh;
> >>>
> >>> -     if (unit) {
> >>> +     if (unit && strlen(unit)) {
> >>>                json_out(os, "\"metric-value\" : \"%f\", \"metric-unit\" : \"%s\"", val, unit);
> >>>                if (thresh != METRIC_THRESHOLD_UNKNOWN) {
> >>>                        json_out(os, "\"metric-threshold\" : \"%s\"",
> >>> --
> >>> 2.34.1
> >>>
>