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

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