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

[Yang Jihong]

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/

Thanks,
Yang