Commit bd0f8895 authored by Andi Kleen's avatar Andi Kleen Committed by Arnaldo Carvalho de Melo
Browse files

perf evsel: Disable branch flags/cycles for --callgraph lbr 



[The kernel patch needed for this is in tip now (b16a5b52 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: default avatarAndi Kleen <ak@linux.intel.com>
Acked-by: default avatarJiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/r/1449879144-29074-1-git-send-email-andi@firstfloor.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent abd82868

tools/perf/util/evsel.c

+13 −1
Original line number Diff line number Diff line
@@ -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;

	}



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