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

[Namhyung Kim]

On Sat, Sep 16, 2023 at 2:24 AM Yang Jihong <yangjihong1@xxxxxxxxxx> wrote:
>
> Hello,
>
> On 2023/9/16 8:14, Namhyung Kim wrote:
> > Hello,
> >
> > On Tue, Sep 12, 2023 at 1:32 PM Arnaldo Carvalho de Melo
> > <acme@xxxxxxxxxx> wrote:
> >>
> >> Em Tue, Sep 12, 2023 at 02:41:56PM +0530, Ravi Bangoria escreveu:
> >>> On 04-Sep-23 8:03 AM, Yang Jihong wrote:
> >>>> 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.
> >>>
> >>> I've re-tested v8 with my simple test.
> >>>
> >>> Tested-by: Ravi Bangoria <ravi.bangoria@xxxxxxx>
> >>
> >>
> >> Thanks, applied to the csets that were still sitting in an umpublished
> >> perf-tools-next local branch, soon public.
> >
> > Now I'm seeing a perf test failure on perf-tools-next.
>
> Uh.. the kernel I was using before didn't support PERF_FORMAT_LOST, so
> forget about supporting PERF_FORMAT_LOST. I've updated the kernel and
> retested it.
>
> The link to the fixed patch is as follows:
> https://lore.kernel.org/all/20230916091641.776031-1-yangjihong1@xxxxxxxxxx/

Thank you for the quick fix!
Namhyung