Commit 5b61adb1 authored by Jiri Olsa's avatar Jiri Olsa Committed by Arnaldo Carvalho de Melo
Browse files

perf evsel: Probe for precise_ip with simple attr 



Currently we probe for precise_ip with user specified perf_event_attr,
which might fail because of unsupported kernel features, which would get
disabled during the open time anyway.

Switching the probe to take place on simple hw cycles, so the following
record sets proper precise_ip:

  # perf record -e cycles:P ls
  # perf evlist -v
  cycles:P: size: 112, ... precise_ip: 3, ...

Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jonas Rabenstein <jonas.rabenstein@studium.uni-erlangen.de>
Cc: Nageswara R Sastry <nasastry@in.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Link: http://lkml.kernel.org/r/20190305152536.21035-7-jolsa@kernel.org


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 90a86bde

tools/perf/util/evlist.c

+20 −5
Original line number Diff line number Diff line
@@ -230,18 +230,33 @@ void perf_evlist__set_leader(struct perf_evlist *evlist) 
	}

}



void perf_event_attr__set_max_precise_ip(struct perf_event_attr *attr)

void perf_event_attr__set_max_precise_ip(struct perf_event_attr *pattr)

{

	attr->precise_ip = 3;

	struct perf_event_attr attr = {

		.type		= PERF_TYPE_HARDWARE,

		.config		= PERF_COUNT_HW_CPU_CYCLES,

		.exclude_kernel	= 1,

		.precise_ip	= 3,

	};



	while (attr->precise_ip != 0) {

		int fd = sys_perf_event_open(attr, 0, -1, -1, 0);

	event_attr_init(&attr);



	/*

	 * Unnamed union member, not supported as struct member named

	 * initializer in older compilers such as gcc 4.4.7

	 */

	attr.sample_period = 1;



	while (attr.precise_ip != 0) {

		int fd = sys_perf_event_open(&attr, 0, -1, -1, 0);

		if (fd != -1) {

			close(fd);

			break;

		}

		--attr->precise_ip;

		--attr.precise_ip;

	}



	pattr->precise_ip = attr.precise_ip;

}



int __perf_evlist__add_default(struct perf_evlist *evlist, bool precise)

tools/perf/util/evsel.c

+0 −8
Original line number Diff line number Diff line
@@ -294,20 +294,12 @@ struct perf_evsel *perf_evsel__new_cycles(bool precise) 


	if (!precise)

		goto new_event;

	/*

	 * Unnamed union member, not supported as struct member named

	 * initializer in older compilers such as gcc 4.4.7

	 *

	 * Just for probing the precise_ip:

	 */

	attr.sample_period = 1;



	perf_event_attr__set_max_precise_ip(&attr);

	/*

	 * Now let the usual logic to set up the perf_event_attr defaults

	 * to kick in when we return and before perf_evsel__open() is called.

	 */

	attr.sample_period = 0;

new_event:

	evsel = perf_evsel__new(&attr);

	if (evsel == NULL)

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