Re: [PATCH v8 0/6] perf record: Track sideband events for all CPUs when tracing selected CPUs

[Yang Jihong]

Hello,

On 2023/9/7 0:08, Arnaldo Carvalho de Melo wrote:
> Em Mon, Sep 04, 2023 at 02:33:34AM +0000, Yang Jihong escreveu:
> > User space tasks can migrate between CPUs, track sideband events for all
> > CPUs.
> >
> > The specific scenarios are as follows:
> >
> >           CPU0                                 CPU1
> >    perf record -C 0 start
> >                                taskA starts to be created and executed
> >                                  -> PERF_RECORD_COMM and PERF_RECORD_MMAP
> >                                     events only deliver to CPU1
> >                                ......
> >                                  |
> >                            migrate to CPU0
> >                                  |
> >    Running on CPU0    <----------/
> >    ...
> >
> >    perf record -C 0 stop
> >
> > Now perf samples the PC of taskA. However, perf does not record the
> > PERF_RECORD_COMM and PERF_RECORD_COMM events of taskA.
> > Therefore, the comm and symbols of taskA cannot be parsed.
> >
> > The sys_perf_event_open invoked is as follows:
> >
> >    # perf --debug verbose=3 record -e cpu-clock -C 1 true
> >    <SNIP>
> >    Opening: cpu-clock
> >    ------------------------------------------------------------
> >    perf_event_attr:
> >      type                             1 (PERF_TYPE_SOFTWARE)
> >      size                             136
> >      config                           0 (PERF_COUNT_SW_CPU_CLOCK)
> >      { sample_period, sample_freq }   4000
> >      sample_type                      IP|TID|TIME|CPU|PERIOD|IDENTIFIER
> >      read_format                      ID|LOST
> >      disabled                         1
> >      inherit                          1
> >      freq                             1
> >      sample_id_all                    1
> >      exclude_guest                    1
> >    ------------------------------------------------------------
> >    sys_perf_event_open: pid -1  cpu 1  group_fd -1  flags 0x8 = 5
> >    Opening: dummy:u
> >    ------------------------------------------------------------
> >    perf_event_attr:
> >      type                             1 (PERF_TYPE_SOFTWARE)
> >      size                             136
> >      config                           0x9 (PERF_COUNT_SW_DUMMY)
> >      { sample_period, sample_freq }   1
> >      sample_type                      IP|TID|TIME|CPU|IDENTIFIER
> >      read_format                      ID|LOST
> >      inherit                          1
> >      exclude_kernel                   1
> >      exclude_hv                       1
> >      mmap                             1
> >      comm                             1
> >      task                             1
> >      sample_id_all                    1
> >      exclude_guest                    1
> >      mmap2                            1
> >      comm_exec                        1
> >      ksymbol                          1
> >      bpf_event                        1
> >    ------------------------------------------------------------
> >    sys_perf_event_open: pid -1  cpu 0  group_fd -1  flags 0x8 = 6
> >    sys_perf_event_open: pid -1  cpu 1  group_fd -1  flags 0x8 = 7
> >    sys_perf_event_open: pid -1  cpu 2  group_fd -1  flags 0x8 = 9
> >    sys_perf_event_open: pid -1  cpu 3  group_fd -1  flags 0x8 = 10
> >    sys_perf_event_open: pid -1  cpu 4  group_fd -1  flags 0x8 = 11
> >    sys_perf_event_open: pid -1  cpu 5  group_fd -1  flags 0x8 = 12
> >    sys_perf_event_open: pid -1  cpu 6  group_fd -1  flags 0x8 = 13
> >    sys_perf_event_open: pid -1  cpu 7  group_fd -1  flags 0x8 = 14
> >    <SNIP>
> >
> > Changes since_v7:
> >   - The condition for requiring system_wide sideband is changed to
> >     "as long as a non-dummy event exists" (patch4).
> >   - Modify the corresponding test case to record only dummy event (patch6).
> >   - Thanks to tested-by tag from Ravi, but because the solution is modified,
> >     the tested-by tag of Ravi is not added to this version.
> >
> > Changes since_v6:
> >   - Patch1:
> >      1. No change.
> >      2. Keep Acked-by tag from Adrian.
> >   - Patch2:
> >      1. Update commit message as suggested by Ian.
> >      2. Keep Acked-by tag from Adrian because code is not modified.
> >   - Patch3:
> >      1. Update comment as suggested by Ian.
> >      2. Merge original patch5 ("perf test: Update base-record & system-wide-dummy attr") as suggested by Ian.
> >      3. Only merge commit, keep Acked-by tag from Adrian.
> >   - Patch4:
> >      1. No change. Because Adrian recommends not changing the function name.
> >      2. Keep Acked-by tag from Adrian.
> >   - Patch5:
> >      1. Add cleanup on trap function as suggested by Ian.
> >      2. Remove Tested-by tag from Adrian because the script is modified.
> >   - Patch6:
> >      1. Add Reviewed-by tag from Ian.
>
> I'm in doubt about these Acked-by/Reviewed-by tags, do they still stand? They are
> not in the latest series, can you please check?

Uh, uh. Because several reviewers have different opinions on the 
solution,  I modified it several times.
Now v8 patchset is different from the previous versions.
I only keep the  Acked-by/Reviewed-by tags of patches that are not 
modified. For patches that have modified the code, I remove the tags.
Therefore, please refer to the v8 series for Acked-by/Reviewed-by tags.
This version needs to be confirmed by reviewers.

Thanks,
Yang