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Date: Tue, 16 Jan 2018 21:06:09 +0800
From: "Jin, Yao" <yao.jin@...ux.intel.com>
To: Jiri Olsa <jolsa@...hat.com>
Cc: acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
mingo@...hat.com, alexander.shishkin@...ux.intel.com,
Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH] perf stat: Ignore error thread when enabling system-wide
--per-thread
Just tested. But looks it's not OK for '--per-thread' case.
jinyao@skl:~/$ ./perf stat --per-thread
WARNING: Ignored open failure for pid 1
WARNING: Ignored open failure for pid 2
WARNING: Ignored open failure for pid 4
WARNING: Ignored open failure for pid 6
WARNING: Ignored open failure for pid 7
WARNING: Ignored open failure for pid 8
WARNING: Ignored open failure for pid 9
WARNING: Ignored open failure for pid 10
......
WARNING: Ignored open failure for pid 11783
WARNING: Ignored open failure for pid 12275
WARNING: Ignored open failure for pid 31733
WARNING: Ignored open failure for pid 31737
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
Thanks
Jin Yao
On 1/16/2018 8:51 PM, Jiri Olsa wrote:
> 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. */
>
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