Messages in this thread | | | Date | Tue, 14 Apr 2020 15:02:09 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCH] perf stat: force error in fallback on :k events |
| |
On Mon, Apr 13, 2020 at 04:55:15PM -0700, Ian Rogers wrote: > From: Stephane Eranian <eranian@google.com> > > When it is not possible for a non-privilege perf command > to monitor at the kernel level (:k), the fallback code forces > a :u. That works if the event was previously monitoring both levels. > But if the event was already constrained to kernel only, then it does > not make sense to restrict it to user only. > Given the code works by exclusion, a kernel only event would have: > attr->exclude_user = 1 > The fallback code would add: > attr->exclude_kernel = 1; > > In the end the end would not monitor in either the user level or kernel > level. In other words, it would count nothing. > > An event programmed to monitor kernel only cannot be switched to user only > without seriously warning the user. > > This patch forces an error in this case to make it clear the request > cannot really be satisfied. > > Signed-off-by: Stephane Eranian <eranian@google.com> > Reviewed-by: Ian Rogers <irogers@google.com> > --- > tools/perf/util/evsel.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c > index d23db6755f51..d1e8862b86ce 100644 > --- a/tools/perf/util/evsel.c > +++ b/tools/perf/util/evsel.c > @@ -2446,6 +2446,13 @@ bool perf_evsel__fallback(struct evsel *evsel, int err, > char *new_name; > const char *sep = ":"; > > + if (evsel->core.attr.exclude_user) { > + scnprintf(msg, msgsize, > +"kernel.perf_event_paranoid=%d, event set to exclude user, so cannot also exclude kernel", > + paranoid); > + return false;
I'm not able to get this error printed, it seems to be overwritten by perf_evsel__open_strerror call
please include perf example with the new output
thanks, jirka
> + } > + > /* Is there already the separator in the name. */ > if (strchr(name, '/') || > strchr(name, ':')) > -- > 2.26.0.110.g2183baf09c-goog >
| |