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SubjectRe: [PATCH V3 1/5] perf/core: Add PERF_SAMPLE_WEIGHT_STRUCT
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On 2/5/2021 5:43 AM, Namhyung Kim wrote:
> On Fri, Feb 5, 2021 at 12:24 AM Liang, Kan <kan.liang@linux.intel.com> wrote:
>>
>> On 2/4/2021 9:00 AM, Namhyung Kim wrote:
>>> Hi Kan,
>>>
>>> On Sat, Jan 30, 2021 at 2:25 AM Liang, Kan <kan.liang@linux.intel.com> wrote:
>>> [SNIP]
>>>> diff --git a/include/uapi/linux/perf_event.h
>>>> b/include/uapi/linux/perf_event.h
>>>> index b15e344..c50718a 100644
>>>> --- a/include/uapi/linux/perf_event.h
>>>> +++ b/include/uapi/linux/perf_event.h
>>>> @@ -145,12 +145,14 @@ enum perf_event_sample_format {
>>>> PERF_SAMPLE_CGROUP = 1U << 21,
>>>> PERF_SAMPLE_DATA_PAGE_SIZE = 1U << 22,
>>>> PERF_SAMPLE_CODE_PAGE_SIZE = 1U << 23,
>>>> + PERF_SAMPLE_WEIGHT_STRUCT = 1U << 24,
>>>>
>>>> - PERF_SAMPLE_MAX = 1U << 24, /* non-ABI */
>>>> + PERF_SAMPLE_MAX = 1U << 25, /* non-ABI */
>>>>
>>>> __PERF_SAMPLE_CALLCHAIN_EARLY = 1ULL << 63, /* non-ABI; internal use */
>>>> };
>>>>
>>>> +#define PERF_SAMPLE_WEIGHT_TYPE (PERF_SAMPLE_WEIGHT |
>>>> PERF_SAMPLE_WEIGHT_STRUCT)
>>>
>>> I'm not sure you want to expose it in the uapi header as it's not
>>> intended to be used IMHO.
>>>
>>
>> I'm not sure I understood, but it's indeed used in the tool patch set.
>>
>> https://lore.kernel.org/lkml/1612296553-21962-6-git-send-email-kan.liang@linux.intel.com/
>
> Well, it's not a big deal.. but I just worried if some users might do
>
> event.attr.sample_type = PERF_SAMPLE_WEIGHT_TYPE;
>

Yes, it's possible. For this case, Kernel returns -EINVAL.

Actually, even without the macro, users may still set PERF_SAMPLE_WEIGHT
| PERF_SAMPLE_WEIGHT_STRUCT manually. We cannot control what a user
sets. I don't think it's a problem as long as the kernel can handle it
properly.

Thanks,
Kan

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