Re: [BUG] perf stat: explicit grouping yields unexpected results

[Stephane Eranian]

On Mon, Dec 2, 2013 at 4:23 PM, Andi Kleen <ak@xxxxxxxxxxxxxxx> wrote:
>> Something like below? user space supply buffer for error string.
>
> That would work, although I was thinking of making it a more
> generic mechanism (store it into task_struct, have a extra
> syscall to retrieve)
>
I don't understand why this need to be so complicated.
Maybe just change the error code in case of group
overcommitment? That way, the tool could distinguish
and report the appropriate error message.


>> jirka
>>
>>
>> ---
>> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
>> index e1802d6..a827870 100644
>> --- a/include/uapi/linux/perf_event.h
>> +++ b/include/uapi/linux/perf_event.h
>> @@ -331,8 +331,8 @@ struct perf_event_attr {
>>        */
>>       __u32   sample_stack_user;
>>
>> -     /* Align to u64. */
>> -     __u32   __reserved_2;
>> +     __u32   errstr_size;
>> +     char    *errstr;
>>  };
>>
>>  #define perf_flags(attr)     (*(&(attr)->read_format + 1))
>>
>
> --
> ak@xxxxxxxxxxxxxxx -- Speaking for myself only
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