[PATCH 3/5] perf, tools: Disable branch flags/cycles for lbr call graph

[Andi Kleen]

From: Andi Kleen <ak@xxxxxxxxxxxxxxx>

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 <ak@xxxxxxxxxxxxxxx>
---
 tools/perf/util/evsel.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index c886b9f..4d8a86c 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -557,6 +557,8 @@ perf_evsel__config_callgraph(struct perf_evsel *evsel,
 					   "Falling back to framepointers.\n");
 			} else {
 				perf_evsel__set_sample_bit(evsel, BRANCH_STACK);
+				perf_evsel__set_sample_bit(evsel, BRANCH_NO_CYCLES);
+				perf_evsel__set_sample_bit(evsel, BRANCH_NO_FLAGS);
 				attr->branch_sample_type = PERF_SAMPLE_BRANCH_USER |
 							PERF_SAMPLE_BRANCH_CALL_STACK;
 			}
@@ -1167,6 +1169,8 @@ fallback_missing_features:
 		evsel->attr.mmap2 = 0;
 	if (perf_missing_features.exclude_guest)
 		evsel->attr.exclude_guest = evsel->attr.exclude_host = 0;
+	evsel->attr.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;
-- 
2.1.0

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