Re: [PATCH] perf trace: Add --max-summary option

[Howard Chu]

Hello Namhyung,

On Wed, Aug 20, 2025 at 5:32 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
> The --max-summary option is to limit the number of output lines for
> syscall summary stats.  The max applies to each entries like thread and
> cgroups.  For total summary, it will just print up to the given number.
>
> For example,
>
>   $ sudo perf trace -as --max-summary 3 sleep 0.1
>
>    ThreadPoolServi (1011651), 114 events, 14.8%
>
>      syscall            calls  errors  total       min       avg       max       stddev
>                                        (msec)    (msec)    (msec)    (msec)        (%)
>      --------------- --------  ------ -------- --------- --------- ---------     ------
>      epoll_wait            38      0    95.589     0.000     2.515    11.153     28.98%
>      futex                  9      0     0.040     0.002     0.004     0.014     28.63%
>      read                  10      0     0.037     0.003     0.004     0.005      4.67%
>
>    sleep (1050529), 250 events, 32.4%
>
>      syscall            calls  errors  total       min       avg       max       stddev
>                                        (msec)    (msec)    (msec)    (msec)        (%)
>      --------------- --------  ------ -------- --------- --------- ---------     ------
>      clock_nanosleep        1      0   100.156   100.156   100.156   100.156      0.00%
>      execve                 4      3     1.020     0.005     0.255     0.989     95.93%
>      openat                36     17     0.416     0.003     0.012     0.029     10.58%
>
>    ...
>
> And this is for per-cgroup summary using BPF.
>
>   $ sudo perf trace -as --max-summary 3 --summary-mode=cgroup --bpf-summary sleep 0.1
>
>    cgroup /user.slice/user-657345.slice/user@657345.service/session.slice/org.gnome.Shell@x11.service, 12 events
>
>      syscall            calls  errors  total       min       avg       max       stddev
>                                        (msec)    (msec)    (msec)    (msec)        (%)
>      --------------- --------  ------ -------- --------- --------- ---------     ------
>      recvmsg                8      7     0.016     0.001     0.002     0.006     39.73%
>      ppoll                  1      0     0.014     0.014     0.014     0.014      0.00%
>      write                  2      0     0.010     0.002     0.005     0.008     61.02%
>
>    cgroup /user.slice/user-657345.slice/session-4.scope, 73 events
>
>      syscall            calls  errors  total       min       avg       max       stddev
>                                        (msec)    (msec)    (msec)    (msec)        (%)
>      --------------- --------  ------ -------- --------- --------- ---------     ------
>      epoll_wait             8      0    13.461     0.010     1.683    12.235     89.66%
>      ioctl                 20      0     0.204     0.001     0.010     0.113     54.01%
>      writev                11      0     0.164     0.004     0.015     0.042     20.34%
>
> Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>

Reviewed-by: Howard Chu <howardchu95@xxxxxxxxx>

Thanks,
Haowei