Re: [PATCH v6] tools/perf/metricgroup: Fix printing event names of metric group with multiple events incase of overlapping events

[Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>]

Em Fri, Feb 21, 2020 at 03:41:21PM +0530, Kajol Jain escreveu:
> Commit f01642e4912b ("perf metricgroup: Support multiple
> events for metricgroup") introduced support for multiple events
> in a metric group. But with the current upstream, metric events
> names are not printed properly incase we try to run multiple
> metric groups with overlapping event.
> 
> With current upstream version, incase of overlapping metric events
> issue is, we always start our comparision logic from start.
> So, the events which already matched with some metric group also
> take part in comparision logic. Because of that when we have overlapping
> events, we end up matching current metric group event with already matched
> one.
> 
> For example, in skylake machine we have metric event CoreIPC and
> Instructions. Both of them need 'inst_retired.any' event value.
> As events in Instructions is subset of events in CoreIPC, they
> endup in pointing to same 'inst_retired.any' value.
> 
> In skylake platform:
> 
> command:# ./perf stat -M CoreIPC,Instructions  -C 0 sleep 1
> 
>  Performance counter stats for 'CPU(s) 0':
> 
>      1,254,992,790      inst_retired.any          # 1254992790.0
>                                                     Instructions
>                                                   #      1.3 CoreIPC
>        977,172,805      cycles
>      1,254,992,756      inst_retired.any
> 
>        1.000802596 seconds time elapsed
> 
> command:# sudo ./perf stat -M UPI,IPC sleep 1
> 
>    Performance counter stats for 'sleep 1':
>            948,650      uops_retired.retire_slots
>            866,182      inst_retired.any          #      0.7 IPC
>            866,182      inst_retired.any
>          1,175,671      cpu_clk_unhalted.thread
> 
> Patch fixes the issue by adding a new bool pointer 'evlist_used' to keep
> track of events which already matched with some group by setting it true.
> So, we skip all used events in list when we start comparision logic.
> Patch also make some changes in comparision logic, incase we get a match
> miss, we discard the whole match and start again with first event id in
> metric event.
> 
> With this patch:
> In skylake platform:
> 
> command:# ./perf stat -M CoreIPC,Instructions  -C 0 sleep 1
> 
>  Performance counter stats for 'CPU(s) 0':
> 
>          3,348,415      inst_retired.any          #      0.3 CoreIPC
>         11,779,026      cycles
>          3,348,381      inst_retired.any          # 3348381.0
>                                                     Instructions
> 
>        1.001649056 seconds time elapsed
> 
> command:# ./perf stat -M UPI,IPC sleep 1
> 
>  Performance counter stats for 'sleep 1':
> 
>          1,023,148      uops_retired.retire_slots #      1.1 UPI
>            924,976      inst_retired.any
>            924,976      inst_retired.any          #      0.6 IPC
>          1,489,414      cpu_clk_unhalted.thread
> 
>        1.003064672 seconds time elapsed
> 
> Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
> Acked-by: Jiri Olsa <jolsa@kernel.org>

This is an area I think needs some improvement, look how it ends up
setting up the inst_retired.any multiple times:

[root@seventh ~]# perf stat -vv -M CoreIPC,Instructions  -C 0 sleep 1
Using CPUID GenuineIntel-6-9E-9
metric expr inst_retired.any / cycles for CoreIPC
found event inst_retired.any
found event cycles
metric expr inst_retired.any for Instructions
found event inst_retired.any
adding {inst_retired.any,cycles}:W,{inst_retired.any}:W
intel_pt default config: tsc,mtc,mtc_period=3,psb_period=3,pt,branch
inst_retired.any -> cpu/event=0xc0,(null)=0x1e8483/
inst_retired.any -> cpu/event=0xc0,(null)=0x1e8483/
------------------------------------------------------------
perf_event_attr:
  type                             4
  size                             120
  config                           0xc0
  sample_type                      IDENTIFIER
  read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING|ID|GROUP
  disabled                         1
  inherit                          1
  exclude_guest                    1
------------------------------------------------------------
sys_perf_event_open: pid -1  cpu 0  group_fd -1  flags 0x8 = 3
------------------------------------------------------------
perf_event_attr:
  size                             120
  sample_type                      IDENTIFIER
  read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING|ID|GROUP
  inherit                          1
  exclude_guest                    1
------------------------------------------------------------
sys_perf_event_open: pid -1  cpu 0  group_fd 3  flags 0x8 = 4
------------------------------------------------------------
perf_event_attr:
  type                             4
  size                             120
  config                           0xc0
  sample_type                      IDENTIFIER
  read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
  disabled                         1
  inherit                          1
  exclude_guest                    1
------------------------------------------------------------
sys_perf_event_open: pid -1  cpu 0  group_fd -1  flags 0x8 = 5
inst_retired.any: 0: 507070 1000948076 1000948076
cycles: 0: 1250258 1000948076 1000948076
inst_retired.any: 0: 507038 1000953052 1000953052
inst_retired.any: 507070 1000948076 1000948076
cycles: 1250258 1000948076 1000948076
inst_retired.any: 507038 1000953052 1000953052

 Performance counter stats for 'CPU(s) 0':

           507,070      inst_retired.any          #      0.4 CoreIPC
         1,250,258      cycles
           507,038      inst_retired.any          # 507038.0 Instructions

       1.000964961 seconds time elapsed

[root@seventh ~]#

And it ends up printing the "inst_retired.any" multiple times, with
different values, as after all two events were allocated, can't we
notice this and set just one inst_retired.any and then when calculating
the metrics just do something like:

  # perf stat -M CoreIPC,Instructions -C 0 sleep 1

 Performance counter stats for 'CPU(s) 0':

           507,070      inst_retired.any          #      0.4 CoreIPC,
						  #  507,070 Instructions
         1,250,258      cycles

       1.000964961 seconds time elapsed
#

?

Ditto for:

    command:# perf stat -M UPI,IPC sleep 1

     Performance counter stats for 'sleep 1':

             1,023,148      uops_retired.retire_slots #      1.1 UPI
               924,976      inst_retired.any
               924,976      inst_retired.any          #      0.6 IPC
             1,489,414      cpu_clk_unhalted.thread

           1.003064672 seconds time elapsed

Wouldn't this be better as:

    command:# perf stat -M UPI,IPC sleep 1

     Performance counter stats for 'sleep 1':

             1,023,148      uops_retired.retire_slots #      1.1 UPI
               924,976      inst_retired.any
             1,489,414      cpu_clk_unhalted.thread   #      0.6 IPC

           1.003064672 seconds time elapsed

This should help to look at many metrics at the same time by requiring
less counters to be allocated, etc, or am I missing something here?

Since this went thru multiple versions and Jiri is satisfied with it,
I'm applying the patch, but please consider this suggestion.

- Arnaldo