perf auxtrace: Fix 'instructions' period of zero

Instruction tracing options (i.e. --itrace) include an option for
sampling instructions at an arbitrary period. e.g.

	--itrace=i10us

means make an 'instructions' sample for every 10us of trace.

Currently the logic does not distinguish between a period of
zero and no period being specified at all, so it gets treated
as the default period which is 100000.  That doesn't really
make sense.

Fix it so that zero period is accepted and treated as meaning
"as often as possible".

In the case of Intel PT that is the same as a period of 1 and
a unit of 'instructions' (i.e. --itrace=i1i).

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1443186956-18718-2-git-send-email-adrian.hunter@intel.com
[ Add a few lines describing this in the Documentation/intel-pt.txt file ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/Documentation/intel-pt.txt b/tools/perf/Documentation/intel-pt.txt
index c94c9de3173ee187f87be72c0ffa128885115c89..886612b50961f0d2bdc6ef3fe154e73a32e3ac6b 100644 (file)
--- a/tools/perf/Documentation/intel-pt.txt
+++ b/tools/perf/Documentation/intel-pt.txt
@@ -707,6 +707,11 @@ on the sample is *not* adjusted and reflects the last known value of TSC.
 
 For Intel PT, the default period is 100us.
 
+Setting it to a zero period means "as often as possible".
+
+In the case of Intel PT that is the same as a period of 1 and a unit of
+'instructions' (i.e. --itrace=i1i).
+
 Also the call chain size (default 16, max. 1024) for instructions or
 transactions events can be specified. e.g.
 

diff --git a/tools/perf/util/auxtrace.c b/tools/perf/util/auxtrace.c
index a980e7c50ee078c47f6579e454572c67616bdc0d..c4993b2e6c50e33909c6f262b0c21d8cce2a830f 100644 (file)
--- a/tools/perf/util/auxtrace.c
+++ b/tools/perf/util/auxtrace.c
@@ -950,6 +950,7 @@ int itrace_parse_synth_opts(const struct option *opt, const char *str,
        const char *p;
        char *endptr;
        bool period_type_set = false;
+       bool period_set = false;
 
        synth_opts->set = true;
 
@@ -971,6 +972,7 @@ int itrace_parse_synth_opts(const struct option *opt, const char *str,
                                p += 1;
                        if (isdigit(*p)) {
                                synth_opts->period = strtoull(p, &endptr, 10);
+                               period_set = true;
                                p = endptr;
                                while (*p == ' ' || *p == ',')
                                        p += 1;
@@ -1053,7 +1055,7 @@ out:
                if (!period_type_set)
                        synth_opts->period_type =
                                        PERF_ITRACE_DEFAULT_PERIOD_TYPE;
-               if (!synth_opts->period)
+               if (!period_set)
                        synth_opts->period = PERF_ITRACE_DEFAULT_PERIOD;
        }
 

diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
index 38942e1eac8f53678948d8ed16bea8b7844fb824..c8bb5ca6a1570052320741af793f0b558e66a422 100644 (file)
--- a/tools/perf/util/intel-pt.c
+++ b/tools/perf/util/intel-pt.c
@@ -720,7 +720,7 @@ static struct intel_pt_queue *intel_pt_alloc_queue(struct intel_pt *pt,
 
                if (!params.period) {
                        params.period_type = INTEL_PT_PERIOD_INSTRUCTIONS;
-                       params.period = 1000;
+                       params.period = 1;
                }
        }