[PATCH V2 06/13] perf tools: option to disable overhead collection

[kan . liang]

From: Kan Liang <kan.liang@xxxxxxxxx>

Perf collects overhead information by default.
A new option --no-profile-cost-info is introduced to disable the
information collection.

Signed-off-by: Kan Liang <kan.liang@xxxxxxxxx>
---
 tools/include/uapi/linux/perf_event.h    | 42 +++++++++++++++++++++++++++++++-
 tools/perf/Documentation/perf-record.txt |  6 +++++
 tools/perf/builtin-record.c              |  2 ++
 tools/perf/perf.h                        |  1 +
 tools/perf/util/evsel.c                  |  1 +
 5 files changed, 51 insertions(+), 1 deletion(-)

diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
index c66a485..bdf2eec 100644
--- a/tools/include/uapi/linux/perf_event.h
+++ b/tools/include/uapi/linux/perf_event.h
@@ -344,7 +344,8 @@ struct perf_event_attr {
 				use_clockid    :  1, /* use @clockid for time fields */
 				context_switch :  1, /* context switch data */
 				write_backward :  1, /* Write ring buffer from end to beginning */
-				__reserved_1   : 36;
+				overhead       :  1, /* Log overhead information */
+				__reserved_1   : 35;
 
 	union {
 		__u32		wakeup_events;	  /* wakeup every n events */
@@ -862,6 +863,17 @@ enum perf_event_type {
 	 */
 	PERF_RECORD_SWITCH_CPU_WIDE		= 15,
 
+	/*
+	 * Records perf overhead
+	 * struct {
+	 *	struct perf_event_header	header;
+	 *	u64				type;
+	 *	struct perf_overhead_entry	entry;
+	 *	struct sample_id		sample_id;
+	 * };
+	 */
+	PERF_RECORD_OVERHEAD			= 16,
+
 	PERF_RECORD_MAX,			/* non-ABI */
 };
 
@@ -980,4 +992,32 @@ struct perf_branch_entry {
 		reserved:44;
 };
 
+/*
+ * The overhead type could be different among architectures.
+ * The common overhead type can be defined from PERF_CORE_OVERHEAD
+ * The arch specific type should be defined from PERF_PMU_OVERHEAD
+ */
+enum perf_record_overhead_type {
+	PERF_CORE_OVERHEAD	 = 0,
+	PERF_CORE_MUX_OVERHEAD	 = 0,
+	PERF_CORE_SB_OVERHEAD,
+
+	PERF_PMU_OVERHEAD	 = 20,
+	PERF_PMU_SAMPLE_OVERHEAD = 20,
+
+	PERF_OVERHEAD_MAX,
+};
+
+/*
+ * single overhead record layout:
+ *
+ *	  nr: Times of overhead happens.
+ *	      E.g. for NMI, nr == times of NMI handler are called.
+ *	time: Total overhead cost(ns)
+ */
+struct perf_overhead_entry {
+	__u64	nr;
+	__u64	time;
+};
+
 #endif /* _UAPI_LINUX_PERF_EVENT_H */
diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 27fc361..29a57f9 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -460,6 +460,12 @@ config terms. For example: 'cycles/overwrite/' and 'instructions/no-overwrite/'.
 
 Implies --tail-synthesize.
 
+--no-profile-cost-info::
+Perf collects profiling time cost by default.
+The time cost includes sampling overhead, multiplexing overhead, side-band
+events overhead and so on.
+This option disable the profiling time cost information collection.
+
 SEE ALSO
 --------
 linkperf:perf-stat[1], linkperf:perf-list[1]
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 67d2a90..73b033b 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1512,6 +1512,8 @@ struct option __record_options[] = {
 		    "Switch output when receive SIGUSR2"),
 	OPT_BOOLEAN(0, "dry-run", &dry_run,
 		    "Parse options then exit"),
+	OPT_BOOLEAN(0, "no-profile-cost-info", &record.opts.no_profile_cost,
+		    "Do not collect perf profiling time cost information"),
 	OPT_END()
 };
 
diff --git a/tools/perf/perf.h b/tools/perf/perf.h
index 9a0236a..59b16d3 100644
--- a/tools/perf/perf.h
+++ b/tools/perf/perf.h
@@ -55,6 +55,7 @@ struct record_opts {
 	bool	     all_user;
 	bool	     tail_synthesize;
 	bool	     overwrite;
+	bool	     no_profile_cost;
 	unsigned int freq;
 	unsigned int mmap_pages;
 	unsigned int auxtrace_mmap_pages;
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index b2365a63..146c191 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -817,6 +817,7 @@ void perf_evsel__config(struct perf_evsel *evsel, struct record_opts *opts,
 	attr->sample_id_all = perf_missing_features.sample_id_all ? 0 : 1;
 	attr->inherit	    = !opts->no_inherit;
 	attr->write_backward = opts->overwrite ? 1 : 0;
+	attr->overhead = !opts->no_profile_cost;
 
 	perf_evsel__set_sample_bit(evsel, IP);
 	perf_evsel__set_sample_bit(evsel, TID);
-- 
2.5.5