Messages in this thread Patch in this message | | | Date | Fri, 12 Jan 2018 12:42:32 +0100 | From | Jiri Olsa <> | Subject | Re: [PATCH V3 10/12] perf top: add overwrite fall back |
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On Thu, Jan 11, 2018 at 09:30:20PM +0000, Liang, Kan wrote: > > 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.
ok
jirka
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