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    Subject[tip:perf/core] perf auxtrace: Fix 'instructions' period of zero
    Commit-ID:  e1791347b5d57d13326cf0114df1a3f3b1c4ca24
    Gitweb: http://git.kernel.org/tip/e1791347b5d57d13326cf0114df1a3f3b1c4ca24
    Author: Adrian Hunter <adrian.hunter@intel.com>
    AuthorDate: Fri, 25 Sep 2015 16:15:32 +0300
    Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
    CommitDate: Mon, 28 Sep 2015 15:50:56 -0300

    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>
    ---
    tools/perf/Documentation/intel-pt.txt | 5 +++++
    tools/perf/util/auxtrace.c | 4 +++-
    tools/perf/util/intel-pt.c | 2 +-
    3 files changed, 9 insertions(+), 2 deletions(-)

    diff --git a/tools/perf/Documentation/intel-pt.txt b/tools/perf/Documentation/intel-pt.txt
    index c94c9de..886612b 100644
    --- 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 a980e7c..c4993b2 100644
    --- 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 38942e1..c8bb5ca 100644
    --- 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;
    }
    }


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