Re: [PATCH v3 0/7] perf: Stream comparison

[Jiri Olsa]

On Mon, Apr 20, 2020 at 09:04:44AM +0800, Jin Yao wrote:

SNIP

>               compute_flag div.c:25                   compute_flag div.c:25
>               compute_flag div.c:22                   compute_flag div.c:22
>                       main div.c:40                           main div.c:40
>                       main div.c:40                           main div.c:40
>                       main div.c:39                           main div.c:39*
> 
> [ Hot chains in old perf data only ]
> 
> hot chain 1:
>              cycles: 2, hits: 4.08%
>          --------------------------
>                       main div.c:42
>               compute_flag div.c:28
> 
> [ Hot chains in new perf data only ]
> 
> hot chain 1:
>                                                     cycles: 36, hits: 3.36%
>                                                  --------------------------
>                                                   __random_r random_r.c:357
>                                                       __random random.c:293
>                                                       __random random.c:293
>                                                       __random random.c:291
>                                                       __random random.c:291
>                                                       __random random.c:291
>                                                       __random random.c:288
>                                                              rand rand.c:27
>                                                              rand rand.c:26
>                                                                    rand@plt
>                                                                    rand@plt
>                                                       compute_flag div.c:25
>                                                       compute_flag div.c:22
>                                                               main div.c:40
>                                                               main div.c:40
> 
> Now we can see, following streams pair is moved to another section
> "[ Hot chains in old perf data but source line changed (*) in new perf data ]"
> 
>             cycles: 1, hits: 26.80%                 cycles: 1, hits: 27.30%
>         ---------------------------              --------------------------
>                       main div.c:39                           main div.c:39*
>                       main div.c:44                           main div.c:44
> 


so I tried following:

  # ./perf record -e cycles:u -b ./perf bench sched pipe
  # ./perf record -e cycles:u -b ./perf bench sched pipe
  # ./perf diff -f --stream --before $PWD --after $PWD >out 2>&1

and the out file looks like this:

  [ Matched hot chains between old perf data and new perf data ]

  [ Hot chains in old perf data but source line changed (*) in new perf data ]

  [ Hot chains in old perf data only ]

  hot chain 1:
               cycles: 0, hits: 4.20%
           --------------------------
                   0xffffffff89c00163

  hot chain 2:
               cycles: 0, hits: 4.11%
           --------------------------
                   0xffffffff89c00163

  hot chain 3:
               cycles: 0, hits: 8.22%
           --------------------------
                   0xffffffff89c00163

  hot chain 4:
               cycles: 0, hits: 5.54%
           --------------------------
                   0xffffffff89c00163

  hot chain 5:
               cycles: 0, hits: 6.10%
           --------------------------
                   0xffffffff89c00163

  [ Hot chains in new perf data only ]

  hot chain 1:
                                                       cycles: 0, hits: 5.21%
                                                   --------------------------
                                                           0xffffffff89c00163

  hot chain 2:
                                                       cycles: 0, hits: 4.79%
                                                   --------------------------
                                                           0xffffffff89c00163

  hot chain 3:
                                                       cycles: 0, hits: 5.44%
                                                   --------------------------
                                                           0xffffffff89c00163

  hot chain 4:
                                                       cycles: 0, hits: 5.50%
                                                   --------------------------
                                                           0xffffffff89c00163

  hot chain 5:
                                                       cycles: 0, hits: 7.14%
                                                   --------------------------
                                                           0xffffffff89c00163


I'd expected more common paths, from what I can see from 'perf report --branch-history'
on bpth perf.data and perf.data.old

jirka