From: Andi Kleen <[email protected]> [The kernel patch needed for this is in tip now (b16a5b52eb9 perf/x86: Add option to disable ...) So this user tools patch to make use of it should be merged now]
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. v2: Switch to use branch_sample_type instead of sample_type. Adjust description. Fix the fallback logic. Signed-off-by: Andi Kleen <[email protected]> Acked-by: Jiri Olsa <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Arnaldo Carvalho de Melo <[email protected]> --- 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 47f033089349..544e4400de13 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; @@ -574,7 +575,9 @@ 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. " @@ -1337,6 +1340,9 @@ 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; @@ -1455,6 +1461,12 @@ 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: -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
