Re: [PATCHv2] perf tools: Force uncore events to system wide monitoring

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Mon, Feb 27, 2017 at 10:48:18AM +0100, Jiri Olsa escreveu:
> On Mon, Feb 27, 2017 at 10:44:13AM +0100, Borislav Petkov wrote:
> > On Mon, Feb 27, 2017 at 10:28:59AM +0100, Jiri Olsa wrote:
> > > would you mind testing new version?
> > 
> > Looks ok to me.
> > 
> > Thanks.
> 
> thanks a lot, full patch attached
> 
> jirka

With it I can't build perf anymore, as I use perf with all make
invocations, so that I can catch when the tool stops working for users
more quickly, like in this case:

  [acme@jouet linux]$ perf stat -e cycles usleep 1
  
   Performance counter stats for 'usleep 1':

             653,232      cycles:u                                                    

         0.005507594 seconds time elapsed

  [acme@jouet linux]$ perf stat usleep 1
  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
  >= 0: Disallow raw tracepoint access by users without CAP_IOC_LOCK
  >= 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

  [acme@jouet linux]$

------------------------------------------------

  If I revert your patch thins are back working:

  [acme@jouet linux]$ perf stat -e cycles usleep 1

   Performance counter stats for 'usleep 1':

           459,396      cycles:u                                                    

       0.001159874 seconds time elapsed

  [acme@jouet linux]$ perf stat usleep 1

   Performance counter stats for 'usleep 1':

          2.022049      task-clock:u (msec)       #    0.181 CPUs utilized          
                 0      context-switches:u        #    0.000 K/sec                  
                 0      cpu-migrations:u          #    0.000 K/sec                  
                48      page-faults:u             #    0.024 M/sec                  
         2,177,301      cycles:u                  #    1.077 GHz                    
           245,106      instructions:u            #    0.11  insn per cycle         
            48,000      branches:u                #   23.738 M/sec                  
             3,936      branch-misses:u           #    8.20% of all branches        

       0.011181563 seconds time elapsed

  [acme@jouet linux]$

---------------------------------------------

Seems related to the auto :u done when the user can't do kernel profiling, etc.

Re-applying your patch, to triple check:

[acme@jouet linux]$ perf stat usleep 1 2>&1 | head -2
Error:
You may not have permission to collect system-wide stats.
[acme@jouet linux]$

------------------------------------------------

Waiting for v3 :-)

- Arnaldo


 
> 
> ---
> Making system wide (-a) the default option if no target
> was specified and one of following conditions is met:
> 
>   - there's no workload specified (current behaviour)
>   - there is workload specified but all requested
>     events are system wide events
> 
> Mixed events core/uncore with workload:
>   $ perf stat -e 'uncore_cbox_0/clockticks/,cycles' sleep 1
> 
>    Performance counter stats for 'sleep 1':
> 
>      <not supported>      uncore_cbox_0/clockticks/
>              980,489      cycles
> 
>          1.000897406 seconds time elapsed
> 
> Uncore event with workload:
>   $ perf stat -e 'uncore_cbox_0/clockticks/' sleep 1
> 
>    Performance counter stats for 'system wide':
> 
>   281,473,897,192,670      uncore_cbox_0/clockticks/
> 
>          1.000833784 seconds time elapsed
> 
> Suggested-by: Borislav Petkov <bp@alien8.de>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: Adrian Hunter <adrian.hunter@intel.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Link: http://lkml.kernel.org/n/tip-rh8kybg6xdadfrw6x6uj37i2@git.kernel.org
> ---
>  tools/perf/builtin-stat.c      | 32 +++++++++++++++++++++++++++++---
>  tools/perf/util/parse-events.c |  5 +++--
>  2 files changed, 32 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index f4f555a67e9b..1320352cda04 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -2350,6 +2350,34 @@ static int __cmd_report(int argc, const char **argv)
>  	return 0;
>  }
>  
> +static void setup_system_wide(int forks)
> +{
> +	/*
> +	 * Make system wide (-a) the default target if
> +	 * no target was specified and one of following
> +	 * conditions is met:
> +	 *
> +	 *   - there's no workload specified
> +	 *   - there is workload specified but all requested
> +	 *     events are system wide events
> +	 */
> +	if (!target__none(&target))
> +		return;
> +
> +	if (!forks)
> +		target.system_wide = true;
> +	else {
> +		struct perf_evsel *counter;
> +
> +		evlist__for_each_entry(evsel_list, counter) {
> +			if (!counter->system_wide)
> +				return;
> +		}
> +
> +		target.system_wide = true;
> +	}
> +}
> +
>  int cmd_stat(int argc, const char **argv, const char *prefix __maybe_unused)
>  {
>  	const char * const stat_usage[] = {
> @@ -2456,9 +2484,7 @@ int cmd_stat(int argc, const char **argv, const char *prefix __maybe_unused)
>  	} else if (big_num_opt == 0) /* User passed --no-big-num */
>  		big_num = false;
>  
> -	/* Make system wide (-a) the default target. */
> -	if (!argc && target__none(&target))
> -		target.system_wide = true;
> +	setup_system_wide(argc);
>  
>  	if (run_count < 0) {
>  		pr_err("Run count must be a positive number\n");
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index 67a8aebc67ab..54355d3caf09 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -316,8 +316,9 @@ __add_event(struct list_head *list, int *idx,
>  		return NULL;
>  
>  	(*idx)++;
> -	evsel->cpus     = cpu_map__get(cpus);
> -	evsel->own_cpus = cpu_map__get(cpus);
> +	evsel->cpus        = cpu_map__get(cpus);
> +	evsel->own_cpus    = cpu_map__get(cpus);
> +	evsel->system_wide = !!cpus;
>  
>  	if (name)
>  		evsel->name = strdup(name);
> -- 
> 2.7.4