Em Fri, Oct 02, 2015 at 06:56:24PM +0200, Jiri Olsa escreveu:
> On Fri, Oct 02, 2015 at 05:04:34AM -0400, kan.li...@intel.com wrote:
> > From: Kan Liang <kan.li...@intel.com>
> >
>
> SNIP
>
> > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> > index a96fb5c..5ef88f7 100644
> > --- a/tools/perf/builtin-stat.c
> > +++ b/tools/perf/builtin-stat.c
> > @@ -1179,7 +1179,7 @@ int cmd_stat(int argc, const char **argv, const char
> > *prefix __maybe_unused)
> > OPT_STRING(0, "post", &post_cmd, "command",
> > "command to run after to the measured command"),
> > OPT_UINTEGER('I', "interval-print", &stat_config.interval,
> > - "print counts at regular interval in ms (>= 100)"),
> > + "print counts at regular interval in ms (>= 10)"),
> > OPT_SET_UINT(0, "per-socket", &stat_config.aggr_mode,
> > "aggregate counts per processor socket", AGGR_SOCKET),
> > OPT_SET_UINT(0, "per-core", &stat_config.aggr_mode,
> > @@ -1332,9 +1332,14 @@ int cmd_stat(int argc, const char **argv, const char
> > *prefix __maybe_unused)
> > thread_map__read_comms(evsel_list->threads);
> >
> > if (interval && interval < 100) {
> > - pr_err("print interval must be >= 100ms\n");
> > - parse_options_usage(stat_usage, options, "I", 1);
> > - goto out;
> > + if (interval < 10) {
> > + pr_err("print interval must be >= 10ms\n");
> > + parse_options_usage(stat_usage, options, "I", 1);
> > + goto out;
> > + } else
> > + pr_warning("print interval < 100ms. "
> > + "The overhead percentage could be high in
> > some cases. "
> > + "Please proceed with caution.\n");
>
> with '-I' 10 this warning flies away quite fast ;-)
>
> I guess it's better than nothing, and I'm not sure
> about putting some sleep after that warning..
>
> Acked-by: Jiri Olsa <jo...@kernel.org>
Right, this should appear in the man page as well, I added the patch
below, we could also print that warning when the workload ends.
- Arnaldo
diff --git a/tools/perf/Documentation/perf-stat.txt
b/tools/perf/Documentation/perf-stat.txt
index 7586fe08ac9a..641caf66ff26 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -130,6 +130,8 @@ perf stat --repeat 10 --null --sync --pre 'make -s
O=defconfig-build/clean' -- m
--interval-print msecs::
Print count deltas every N milliseconds (minimum: 10ms)
example: perf stat -I 1000 -e cycles -a sleep 5
+ The overhead percentage could be high in some cases, for instance
+ with small, sub 100ms intervals. Use with caution.
--per-socket::
Aggregate counts per processor socket for system-wide mode measurements. This
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
