Re: [PATCH v3 01/15] perf/mem: Introduce PERF_MEM_LVLNUM_{EXTN_MEM|IO}

[Ravi Bangoria]

On 30-Sep-22 7:47 PM, Liang, Kan wrote:
> 
> 
> On 2022-09-30 8:50 a.m., Ravi Bangoria wrote:
>> On 30-Sep-22 4:18 PM, kajoljain wrote:
>>>
>>>
>>> On 9/28/22 15:27, Ravi Bangoria wrote:
>>>> PERF_MEM_LVLNUM_EXTN_MEM which can be used to indicate accesses to
>>>> extension memory like CXL etc. PERF_MEM_LVL_IO can be used for IO
>>>> accesses but it can not distinguish between local and remote IO.
>>>> Introduce new field PERF_MEM_LVLNUM_IO which can be clubbed with
>>>> PERF_MEM_REMOTE_REMOTE to indicate Remote IO accesses.
>>>>
>>>> Signed-off-by: Ravi Bangoria <ravi.bangoria@xxxxxxx>
>>>> ---
>>>>  include/uapi/linux/perf_event.h | 4 +++-
>>>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
>>>> index e639c74cf5fb..4ae3c249f675 100644
>>>> --- a/include/uapi/linux/perf_event.h
>>>> +++ b/include/uapi/linux/perf_event.h
>>>> @@ -1336,7 +1336,9 @@ union perf_mem_data_src {
>>>>  #define PERF_MEM_LVLNUM_L2	0x02 /* L2 */
>>>>  #define PERF_MEM_LVLNUM_L3	0x03 /* L3 */
>>>>  #define PERF_MEM_LVLNUM_L4	0x04 /* L4 */
>>>> -/* 5-0xa available */
>>>> +/* 5-0x8 available */
>>>> +#define PERF_MEM_LVLNUM_EXTN_MEM 0x09 /* Extension memory */
>>>
>>> Hi Ravi,
>>>     Here we are adding entry explicitly for accesses to Extension memory
>>> like CXL. In future if we want to extend it for cache or other accesses
>>> , we again need to add new entries.
>>> Can we rather add single entry say PERF_MEM_LVLNUM_EXTN and further can
>>> use reserved bits to specify memory/cache?
>>
>> Is everybody okay with this:
>>
>> #define PERF_MEM_LVLNUM_EXTN	0x09 /* CXL */
> 
> I think a generic name, PERF_MEM_LVLNUM_EXTN, only make sense, when it
> wants to include all the types of the Extension memory, e.g., CXL, PMEM,
> HBM, etc. Then we can set this bit and the corresponding CXL bits to
> understand the real source. Is it the case here?
> 
> But if it's only for the CXL, I think it's better to use a dedicated
> name, PERF_MEM_LVLNUM_CXL. (as we did for PMEM, PERF_MEM_LVLNUM_PMEM).
> If so, I don't think we need the PERF_MEM_EXTN_CXL_ANY.

Ok. For now, I think below is good enough? Later we can introduce new
variable to provide type of cxl device.