Commit 28667a52 authored by Riccardo Mancini's avatar Riccardo Mancini Committed by Arnaldo Carvalho de Melo
Browse files

perf evsel: Handle precise_ip fallback in evsel__open_cpu() 



This is another patch in the effort to separate the fallback mechanisms
from the open itself.

In case of precise_ip fallback, the original precise_ip will be stored
in the evsel (it was stored in a local variable) and the open will be
retried. Since the precise_ip fallback will be the first in the chain of
fallbacks, there should be no functional change with this patch.

Signed-off-by: default avatarRiccardo Mancini <rickyman7@gmail.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/74208c433d2024a6c4af9c0b140b54ed6b5ea810.1629490974.git.rickyman7@gmail.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 91233d00

tools/perf/util/evsel.c

+26 −33
Original line number Diff line number Diff line
@@ -1709,43 +1709,30 @@ static void display_attr(struct perf_event_attr *attr) 
	}

}



static int perf_event_open(struct evsel *evsel,

			   pid_t pid, int cpu, int group_fd)

bool evsel__precise_ip_fallback(struct evsel *evsel)

{

	int precise_ip = evsel->core.attr.precise_ip;

	int fd;



	while (1) {

		pr_debug2_peo("sys_perf_event_open: pid %d  cpu %d  group_fd %d  flags %#lx",

			  pid, cpu, group_fd, evsel->open_flags);



		fd = sys_perf_event_open(&evsel->core.attr, pid, cpu, group_fd, evsel->open_flags);

		if (fd >= 0)

			break;



	/* Do not try less precise if not requested. */

	if (!evsel->precise_max)

			break;

		return false;



	/*

	 * We tried all the precise_ip values, and it's

	 * still failing, so leave it to standard fallback.

	 */

	if (!evsel->core.attr.precise_ip) {

			evsel->core.attr.precise_ip = precise_ip;

			break;

		evsel->core.attr.precise_ip = evsel->precise_ip_original;

		return false;

	}



		pr_debug2_peo("\nsys_perf_event_open failed, error %d\n", -ENOTSUP);

	if (!evsel->precise_ip_original)

		evsel->precise_ip_original = evsel->core.attr.precise_ip;



	evsel->core.attr.precise_ip--;

	pr_debug2_peo("decreasing precise_ip by one (%d)\n", evsel->core.attr.precise_ip);

	display_attr(&evsel->core.attr);

	return true;

}



	return fd;

}





static struct perf_cpu_map *empty_cpu_map;

static struct perf_thread_map *empty_thread_map;
@@ -2004,8 +1991,11 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus, 


			test_attr__ready();



			fd = perf_event_open(evsel, pid, cpus->map[cpu],

					     group_fd);

			pr_debug2_peo("sys_perf_event_open: pid %d  cpu %d  group_fd %d  flags %#lx",

				pid, cpus->map[cpu], group_fd, evsel->open_flags);



			fd = sys_perf_event_open(&evsel->core.attr, pid, cpus->map[cpu],

						group_fd, evsel->open_flags);



			FD(evsel, cpu, thread) = fd;
@@ -2058,6 +2048,9 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus, 
	return 0;



try_fallback:

	if (evsel__precise_ip_fallback(evsel))

		goto retry_open;



	if (evsel__ignore_missing_thread(evsel, cpus->nr, cpu, threads, thread, err)) {

		/* We just removed 1 thread, so lower the upper nthreads limit. */

		nthreads--;

tools/perf/util/evsel.h

+2 −0
Original line number Diff line number Diff line
@@ -151,6 +151,7 @@ struct evsel { 
		struct bperf_follower_bpf *follower_skel;

	};

	unsigned long		open_flags;

	int			precise_ip_original;

};



struct perf_missing_features {
@@ -298,6 +299,7 @@ bool evsel__ignore_missing_thread(struct evsel *evsel, 
				  int nr_cpus, int cpu,

				  struct perf_thread_map *threads,

				  int thread, int err);

bool evsel__precise_ip_fallback(struct evsel *evsel);



struct perf_sample;