Messages in this thread | | | From | Ian Rogers <> | Date | Tue, 14 Apr 2020 09:21:43 -0700 | Subject | Re: [PATCH] perf stat: force error in fallback on :k events |
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On Tue, Apr 14, 2020 at 8:12 AM Jiri Olsa <jolsa@redhat.com> wrote: > > On Tue, Apr 14, 2020 at 07:38:17AM -0700, Ian Rogers wrote: > > On Tue, Apr 14, 2020 at 6:02 AM Jiri Olsa <jolsa@redhat.com> wrote: > > > > > > 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 > > > > Agreed, it is possible the change builtin-top/sched/record so that on > > error the msg is checked and dumped in verbose mode. I think it is > > also fine to just remove the scnprintf. Do you have a preference? > > not sure ;-) but let's make sure we don't remove some expected output > > jirka
I went the easier route as I don't think the new error message adds anything over the perf_evsel__open_strerror message. v2 is here: https://lore.kernel.org/lkml/20200414161550.225588-1-irogers@google.com/T/#u
Thanks, Ian
> > > > Thanks, > > Ian > > > > > thanks, > > > jirka > > > > > > > + } > > > > + > > > > /* Is there already the separator in the name. */ > > > > if (strchr(name, '/') || > > > > strchr(name, ':')) > > > > -- > > > > 2.26.0.110.g2183baf09c-goog > > > > > > > > > >
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