[RFC PATCH v1 24/37] perf evsel: handle precise_ip fallback in evsel__open_cpu
From: Riccardo Mancini <hidden>
Date: 2021-08-21 09:21:58
Also in:
lkml
Subsystem:
performance events subsystem, the rest · Maintainers:
Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, Linus Torvalds
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: Riccardo Mancini <redacted> --- tools/perf/util/evsel.c | 59 ++++++++++++++++++----------------------- tools/perf/util/evsel.h | 2 ++ 2 files changed, 28 insertions(+), 33 deletions(-)
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 3e556afed8dd396c..2e95416b8320c6b9 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c@@ -1709,42 +1709,29 @@ 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; - - /* - * 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; - } + /* Do not try less precise if not requested. */ + if (!evsel->precise_max) + return false; - pr_debug2_peo("\nsys_perf_event_open failed, error %d\n", -ENOTSUP); - 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); + /* + * 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 = evsel->precise_ip_original; + return false; } - return fd; -} + 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; +} 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--;
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 661d2677a19b6248..0a245afab2d87d74 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h@@ -150,6 +150,7 @@ struct evsel { struct bperf_follower_bpf *follower_skel; }; unsigned long open_flags; + int precise_ip_original; }; struct perf_missing_features {
@@ -297,6 +298,7 @@ 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;
--
2.31.1