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

[Yang Jihong <yangjihong1@huawei.com>]

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@kernel.org> 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@amd.com>
>>
>>
>> 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@huawei.com/

Thanks,
Yang