On Tue, Jan 16, 2018 at 11:43:08PM +0800, Jin Yao wrote:
> 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
could we use the existing code like in attached patch?
we might also swap following warning for some generic one:
WARNING: Ignored open failure for pid 28392
jirka
---
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 98bf9d32f222..f9d4d3ad6fc5 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -276,6 +276,9 @@ static int create_perf_stat_counter(struct perf_evsel
*evsel)
attr->enable_on_exec = 1;
}
+ if (stat_config.aggr_mode == AGGR_THREAD)
+ evsel->ignore_missing_thread = true;
+
if (target__has_cpu(&target) && !target__has_per_thread(&target))
return perf_evsel__open_per_cpu(evsel, perf_evsel__cpus(evsel));
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 8f971a2301d1..509ee175bc97 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1656,7 +1656,7 @@ static bool ignore_missing_thread(struct perf_evsel
*evsel,
return false;
/* The -ESRCH is perf event syscall errno for pid's not found. */
- if (err != -ESRCH)
+ if (err != -ESRCH && err != -EACCES)
return false;
/* If there's only one thread, let it fail. */
