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perf auxtrace: Fix 'instructions' period of zero

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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>
This commit is contained in:
Adrian Hunter 2015-09-25 16:15:32 +03:00 committed by Arnaldo Carvalho de Melo
parent 7c422f5572
commit e1791347b5
3 changed files with 9 additions and 2 deletions
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5
tools/perf/Documentation/intel-pt.txt
View File

@ -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.

4
tools/perf/util/auxtrace.c
View File

@ -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;
}

2
tools/perf/util/intel-pt.c
View File

@ -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;
}
}