Re: What perf_event_paranoid can do?

[Lin Ming <minggr@gmail.com>]

2011/3/21 陳韋任 <chenwj@iis.sinica.edu.tw>:
> Hi, Lin
>
>> It's used to control if some action is allowed or not for normal user.
>> See comments at kernel/perf_event.c:
>>
>> /*
>>  * perf event paranoia level:
>>  *  -1 - not paranoid at all
>>  *   0 - disallow raw tracepoint access for unpriv
>>  *   1 - disallow cpu events for unpriv
>>  *   2 - disallow kernel profiling for unpriv
>>  */
>
>  I assume -1 give normal user the most high level privilege,
> but it doesn't work. I have tried -1 through 2, but none of
> them works. Any suggestion? Or maybe the event "branches" does
> not support PBES modifier (pp)?

In x86_setup_perfctr:

        /*
         * Branch tracing:
         */
        if ((attr->config == PERF_COUNT_HW_BRANCH_INSTRUCTIONS) &&
            (hwc->sample_period == 1)) {
                /* BTS is not supported by this architecture. */
                if (!x86_pmu.bts_active)
                        return -EOPNOTSUPP;

                /* BTS is currently only allowed for user-mode. */
                if (!attr->exclude_kernel)
                        return -EOPNOTSUPP;
        }

Does your CPU support PEBS? Please attach below output.

dmesg |grep "Performance Events"

Lin Ming

>
>  Thanks!
>
> Regards,
> chenwj
>
> --
> Wei-Ren Chen (陳韋任)
> Parallel Processing Lab, Institute of Information Science,
> Academia Sinica, Taiwan (R.O.C.)
> Tel:886-2-2788-3799 #1667
>