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From:   Namhyung Kim <namhyung@kernel.org>
Date:   Fri, 15 Sep 2023 17:14:09 -0700
Message-ID: <CAM9d7cgNH2+zhSAmA3en_6as915UsF25MoLbfjE350tAP43Bog@mail.gmail.com>
Subject: Re: [PATCH v8 0/6] perf record: Track sideband events for all CPUs
 when tracing selected CPUs
To:     Arnaldo Carvalho de Melo <acme@kernel.org>
Cc:     Ravi Bangoria <ravi.bangoria@amd.com>,
        Yang Jihong <yangjihong1@huawei.com>, peterz@infradead.org,
        mingo@redhat.com, mark.rutland@arm.com,
        alexander.shishkin@linux.intel.com, jolsa@kernel.org,
        irogers@google.com, adrian.hunter@intel.com,
        kan.liang@linux.intel.com, james.clark@arm.com,
        tmricht@linux.ibm.com, ak@linux.intel.com,
        anshuman.khandual@arm.com, linux-kernel@vger.kernel.org,
        linux-perf-users@vger.kernel.org
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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.


$ sudo ./perf test -v 17
 17: Setup struct perf_event_attr                                    :
--- start ---
test child forked, pid 1616372
Using CPUID GenuineIntel-6-8C-1
running './tests/attr/test-record-branch-filter-k'
running './tests/attr/test-record-period'
running './tests/attr/test-record-graph-default'
test limitation '!aarch64'
excluded architecture list ['aarch64']
running './tests/attr/test-record-branch-filter-any'
running './tests/attr/test-record-data'
running './tests/attr/test-stat-detailed-1'
running './tests/attr/test-record-branch-filter-hv'
running './tests/attr/test-record-graph-fp'
test limitation '!aarch64'
excluded architecture list ['aarch64']
running './tests/attr/test-record-basic'
running './tests/attr/test-record-group2'
running './tests/attr/test-stat-detailed-3'
running './tests/attr/test-record-branch-any'
running './tests/attr/test-record-branch-filter-ind_call'
running './tests/attr/test-stat-detailed-2'
running './tests/attr/test-record-group1'
running './tests/attr/test-record-count'
running './tests/attr/test-record-no-samples'
running './tests/attr/test-record-graph-dwarf'
running './tests/attr/test-record-spe-period'
test limitation 'aarch64'
skipped [x86_64] './tests/attr/test-record-spe-period'
running './tests/attr/test-record-graph-fp-aarch64'
test limitation 'aarch64'
skipped [x86_64] './tests/attr/test-record-graph-fp-aarch64'
running './tests/attr/test-record-freq'
running './tests/attr/test-record-pfm-period'
running './tests/attr/test-record-no-buffering'
running './tests/attr/test-record-no-inherit'
running './tests/attr/test-record-branch-filter-any_ret'
running './tests/attr/test-record-raw'
running './tests/attr/test-record-dummy-C0'
expected read_format=4, got 20
FAILED './tests/attr/test-record-dummy-C0' - match failure
test child finished with -1
---- end ----
Setup struct perf_event_attr: FAILED!