On Tue, Oct 20, 2015 at 11:46:35AM -0700, Andi Kleen wrote:
> From: Andi Kleen <[email protected]>
>
> Automatically disable collecting branch flags and cycles with
> --call-graph lbr. This allows avoiding a bunch of extra MSR
> reads in the PMI on Skylake.
>
> When the kernel doesn't support the new flags they are automatically
> cleared in the fallback code.
>
> Signed-off-by: Andi Kleen <[email protected]>
> ---
Arnaldo, ACK?
> tools/perf/util/evsel.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 8be867c..e8724b4 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -36,6 +36,7 @@ static struct {
> bool cloexec;
> bool clockid;
> bool clockid_wrong;
> + bool lbr_flags;
> } perf_missing_features;
>
> static clockid_t clockid;
> @@ -573,7 +574,9 @@ perf_evsel__config_callgraph(struct perf_evsel *evsel,
> } else {
> perf_evsel__set_sample_bit(evsel, BRANCH_STACK);
> attr->branch_sample_type =
> PERF_SAMPLE_BRANCH_USER |
> -
> PERF_SAMPLE_BRANCH_CALL_STACK;
> +
> PERF_SAMPLE_BRANCH_CALL_STACK |
> +
> PERF_SAMPLE_BRANCH_NO_CYCLES |
> +
> PERF_SAMPLE_BRANCH_NO_FLAGS;
> }
> } else
> pr_warning("Cannot use LBR callstack with branch
> stack. "
> @@ -1312,6 +1315,9 @@ fallback_missing_features:
> evsel->attr.mmap2 = 0;
> if (perf_missing_features.exclude_guest)
> evsel->attr.exclude_guest = evsel->attr.exclude_host = 0;
> + if (perf_missing_features.lbr_flags)
> + evsel->attr.branch_sample_type &= ~(PERF_SAMPLE_BRANCH_NO_FLAGS
> |
> + PERF_SAMPLE_BRANCH_NO_CYCLES);
> retry_sample_id:
> if (perf_missing_features.sample_id_all)
> evsel->attr.sample_id_all = 0;
> @@ -1414,6 +1420,12 @@ try_fallback:
> } else if (!perf_missing_features.sample_id_all) {
> perf_missing_features.sample_id_all = true;
> goto retry_sample_id;
> + } else if (!perf_missing_features.lbr_flags &&
> + (evsel->attr.branch_sample_type &
> + (PERF_SAMPLE_BRANCH_NO_CYCLES |
> + PERF_SAMPLE_BRANCH_NO_FLAGS))) {
> + perf_missing_features.lbr_flags = true;
> + goto fallback_missing_features;
> }
>
> out_close:
> --
> 2.4.3
>
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