Messages in this thread | | | From | "Liang, Kan" <> | Subject | RE: [PATCH V3 10/12] perf top: add overwrite fall back | Date | Thu, 11 Jan 2018 21:30:20 +0000 |
| |
> On Thu, Dec 21, 2017 at 10:08:52AM -0800, kan.liang@intel.com wrote: > > From: Kan Liang <kan.liang@intel.com> > > > > Switch to non-overwrite mode if kernel doesnot support overwrite > > ringbuffer. > > > > It's only effect when overwrite mode is supported. > > No change to current behavior. > > > > Signed-off-by: Kan Liang <kan.liang@intel.com> > > --- > > tools/perf/builtin-top.c | 36 ++++++++++++++++++++++++++++++++++++ > > 1 file changed, 36 insertions(+) > > > > diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c > > index 4b85e7b..8d19ef7 100644 > > --- a/tools/perf/builtin-top.c > > +++ b/tools/perf/builtin-top.c > > @@ -931,6 +931,27 @@ static int perf_top_overwrite_check(struct > perf_top *top) > > return 0; > > } > > > > +static int perf_top_overwrite_fallback(struct perf_top *top, > > + struct perf_evsel *evsel) > > +{ > > + struct record_opts *opts = &top->record_opts; > > + struct perf_evlist *evlist = top->evlist; > > + struct perf_evsel *counter; > > + > > + if (!opts->overwrite) > > + return 0; > > + > > + /* only fall back when first event fails */ > > + if (evsel != perf_evlist__first(evlist)) > > + return 0; > > + > > + evlist__for_each_entry(evlist, counter) > > + counter->attr.write_backward = false; > > + opts->overwrite = false; > > + ui__warning("fall back to non-overwrite mode\n"); > > + return 1; > > +} > > we already do that for evsel in perf_evsel__open.. could we make > this fallback on one place only? > > checking the code, why don't we follow the > perf_missing_features.write_backward > like we do for other features in the perf_evsel__open and set > write_backward accordingly, like in attached patch. >
No, the per-event fallback is explicitly disabled in perf_evsel__open. You may refer to commit 32a951b4fd6b ("perf evlist: Drop redundant evsel->overwrite indicator)".
Now, only perf top supports the whole fallback. So it is specially handled.
Thanks, Kan
> jirka > > > --- > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c > index dbd80268de54..89253f4ff9ee 100644 > --- a/tools/perf/util/evsel.c > +++ b/tools/perf/util/evsel.c > @@ -1683,9 +1683,6 @@ int perf_evsel__open(struct perf_evsel *evsel, > struct cpu_map *cpus, > int pid = -1, err; > enum { NO_CHANGE, SET_TO_MAX, INCREASED_MAX } set_rlimit = > NO_CHANGE; > > - if (perf_missing_features.write_backward && evsel- > >attr.write_backward) > - return -EINVAL; > - > if (cpus == NULL) { > static struct cpu_map *empty_cpu_map; > > @@ -1725,6 +1722,8 @@ int perf_evsel__open(struct perf_evsel *evsel, > struct cpu_map *cpus, > } > > fallback_missing_features: > + if (perf_missing_features.write_backward) > + evsel->attr.write_backward = false; > if (perf_missing_features.clockid_wrong) > evsel->attr.clockid = CLOCK_MONOTONIC; /* should always > work */ > if (perf_missing_features.clockid) {
| |