From ab6c79b819f5a50cf41a11ebec17bef63b530333 Mon Sep 17 00:00:00 2001 From: Jin Yao Date: Tue, 16 Jan 2018 23:43:08 +0800 Subject: [PATCH] perf stat: Ignore error thread when enabling system-wide --per-thread If we execute 'perf stat --per-thread' with non-root account (even set kernel.perf_event_paranoid = -1 yet), it reports the error: jinyao@skl:~$ perf stat --per-thread Error: You may not have permission to collect system-wide stats. Consider tweaking /proc/sys/kernel/perf_event_paranoid, which controls use of the performance events system by unprivileged users (without CAP_SYS_ADMIN). The current value is 2: -1: Allow use of (almost) all events by all users Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK >= 0: Disallow ftrace function tracepoint by users without CAP_SYS_ADMIN Disallow raw tracepoint access by users without CAP_SYS_ADMIN >= 1: Disallow CPU event access by users without CAP_SYS_ADMIN >= 2: Disallow kernel profiling by users without CAP_SYS_ADMIN To make this setting permanent, edit /etc/sysctl.conf too, e.g.: kernel.perf_event_paranoid = -1 Perhaps the ptrace rule doesn't allow to trace some processes. But anyway the global --per-thread mode had better ignore such errors and continue working on other threads. This patch will record the index of error thread in perf_evsel__open() and remove this thread before retrying. For example (run with non-root, kernel.perf_event_paranoid isn't set): jinyao@skl:~$ perf stat --per-thread ^C Performance counter stats for 'system wide': vmstat-3458 6.171984 cpu-clock:u (msec) # 0.000 CPUs utilized perf-3670 0.515599 cpu-clock:u (msec) # 0.000 CPUs utilized vmstat-3458 1,163,643 cycles:u # 0.189 GHz perf-3670 40,881 cycles:u # 0.079 GHz vmstat-3458 1,410,238 instructions:u # 1.21 insn per cycle perf-3670 3,536 instructions:u # 0.09 insn per cycle vmstat-3458 288,937 branches:u # 46.814 M/sec perf-3670 936 branches:u # 1.815 M/sec vmstat-3458 15,195 branch-misses:u # 5.26% of all branches perf-3670 76 branch-misses:u # 8.12% of all branches 12.651675247 seconds time elapsed Signed-off-by: Jin Yao Acked-by: Jiri Olsa Tested-by: Arnaldo Carvalho de Melo Cc: Alexander Shishkin Cc: Andi Kleen Cc: Kan Liang Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1516117388-10120-1-git-send-email-yao.jin@linux.intel.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-stat.c | 14 +++++++++++++- tools/perf/util/evsel.c | 3 +++ tools/perf/util/thread_map.c | 1 + tools/perf/util/thread_map.h | 1 + 4 files changed, 18 insertions(+), 1 deletion(-) diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c index fadcff52cd09..6214d2b220b2 100644 --- a/tools/perf/builtin-stat.c +++ b/tools/perf/builtin-stat.c @@ -637,7 +637,19 @@ try_again: if (verbose > 0) ui__warning("%s\n", msg); goto try_again; - } + } else if (target__has_per_thread(&target) && + evsel_list->threads && + evsel_list->threads->err_thread != -1) { + /* + * For global --per-thread case, skip current + * error thread. + */ + if (!thread_map__remove(evsel_list->threads, + evsel_list->threads->err_thread)) { + evsel_list->threads->err_thread = -1; + goto try_again; + } + } perf_evsel__open_strerror(counter, &target, errno, msg, sizeof(msg)); diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c index ef351688b797..b56e1c2ddaee 100644 --- a/tools/perf/util/evsel.c +++ b/tools/perf/util/evsel.c @@ -1915,6 +1915,9 @@ try_fallback: goto fallback_missing_features; } out_close: + if (err) + threads->err_thread = thread; + do { while (--thread >= 0) { close(FD(evsel, cpu, thread)); diff --git a/tools/perf/util/thread_map.c b/tools/perf/util/thread_map.c index 729dad8f412d..5d467d8ae9ab 100644 --- a/tools/perf/util/thread_map.c +++ b/tools/perf/util/thread_map.c @@ -32,6 +32,7 @@ static void thread_map__reset(struct thread_map *map, int start, int nr) size_t size = (nr - start) * sizeof(map->map[0]); memset(&map->map[start], 0, size); + map->err_thread = -1; } static struct thread_map *thread_map__realloc(struct thread_map *map, int nr) diff --git a/tools/perf/util/thread_map.h b/tools/perf/util/thread_map.h index 5ec91cfd1869..2f689c90a8c6 100644 --- a/tools/perf/util/thread_map.h +++ b/tools/perf/util/thread_map.h @@ -14,6 +14,7 @@ struct thread_map_data { struct thread_map { refcount_t refcnt; int nr; + int err_thread; struct thread_map_data map[]; };