Re: [RFC] perf record: Add option to print perf_event_open args and return value

[Jiri Olsa <jolsa@redhat.com>]

On Fri, Nov 08, 2019 at 09:29:49AM +0530, Ravi Bangoria wrote:
> Perf record with verbose=2 already prints this information along with
> whole lot of other traces which requires lot of scrolling. I thought
> to show this information in verbose=1 but I fear that it will be too
> much for level 1. So finally created a new option specifically for
> printing this.
> 
> Sample o/p:
>   $ ./perf record --peo-args -- ls > /dev/null
>   ------------------------------------------------------------
>   perf_event_attr:
>     size                             112
>     { sample_period, sample_freq }   4000
>     sample_type                      IP|TID|TIME|PERIOD
>     read_format                      ID
>     disabled                         1
>     inherit                          1
>     exclude_kernel                   1
>     mmap                             1
>     comm                             1
>     freq                             1
>     enable_on_exec                   1
>     task                             1
>     precise_ip                       3
>     sample_id_all                    1
>     exclude_guest                    1
>     mmap2                            1
>     comm_exec                        1
>     ksymbol                          1
>     bpf_event                        1
>   ------------------------------------------------------------
>   sys_perf_event_open: pid 4308  cpu 0  group_fd -1  flags 0x8 = 4
>   sys_perf_event_open: pid 4308  cpu 1  group_fd -1  flags 0x8 = 5
>   sys_perf_event_open: pid 4308  cpu 2  group_fd -1  flags 0x8 = 6
>   sys_perf_event_open: pid 4308  cpu 3  group_fd -1  flags 0x8 = 8
>   sys_perf_event_open: pid 4308  cpu 4  group_fd -1  flags 0x8 = 9
>   sys_perf_event_open: pid 4308  cpu 5  group_fd -1  flags 0x8 = 10
>   sys_perf_event_open: pid 4308  cpu 6  group_fd -1  flags 0x8 = 11
>   sys_perf_event_open: pid 4308  cpu 7  group_fd -1  flags 0x8 = 12
>   ------------------------------------------------------------
>   perf_event_attr:
>     type                             1
>     size                             112
>     config                           0x9
>     watermark                        1
>     sample_id_all                    1
>     bpf_event                        1
>     { wakeup_events, wakeup_watermark } 1
>   ------------------------------------------------------------
>   sys_perf_event_open: pid -1  cpu 0  group_fd -1  flags 0x8
>   sys_perf_event_open failed, error -13
>   [ perf record: Woken up 1 times to write data ]
>   [ perf record: Captured and wrote 0.002 MB perf.data (9 samples) ]
> 
> Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>

right, -vv is already poluted ;-) but we have the perf --debug
option for specific debug:

       --debug
           Setup debug variable (see list below) in value range (0, 10). Use like: --debug verbose # sets verbose = 1 --debug verbose=2 # sets verbose = 2

               List of debug variables allowed to set:
                 verbose          - general debug messages
                 ordered-events   - ordered events object debug messages
                 data-convert     - data convert command debug messages
                 stderr           - write debug output (option -v) to stderr
                                    in browser mode

so I think something like this would fit better:

  perf --debug event-open[=X] record ...  
  perf --debug perf-event-open[=X] record ...  

you can have different levels for specific debug output,
also it should also stay part of -vv output

thanks,
jirka