Messages in this thread | | | Date | Mon, 30 Mar 2015 21:34:11 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] perf, record: Add clockid parameter |
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On Mon, Mar 30, 2015 at 11:33:42AM -0600, David Ahern wrote: > On 3/28/15 1:55 AM, Peter Zijlstra wrote: > >@@ -761,6 +762,11 @@ void perf_evsel__config(struct perf_evse > > attr->disabled = 0; > > attr->enable_on_exec = 0; > > } > >+ > >+ if (opts->clockid >= 0) { > >+ attr->use_clockid = 1; > >+ attr->clockid = opts->clockid; > >+ } > > } > > One more: you need to set attr->clockid to -1 if use_clockid is not set so > that the analysis side knows whether attr->clockid was used. Otherwise it > defaults to 0 == CLOCK_REALTIME which is misleading. > > > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c > index 1abf6919b8a2..27679ab38511 100644 > --- a/tools/perf/util/evsel.c > +++ b/tools/perf/util/evsel.c > @@ -766,7 +766,8 @@ void perf_evsel__config(struct perf_evsel *evsel, struct > record_opts *opts) > if (opts->clockid >= 0) { > attr->use_clockid = 1; > attr->clockid = opts->clockid; > - } > + } else > + attr->clockid = -1; > }
No, we must not have a !0 value in ->clockid when we do not set use_clockid. The kernel checks for nonzero tail values.
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