linux-kernel - Re: [PATCH v3 01/15] perf/mem: Introduce PERF_MEM_LVLNUM_{EXTN

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Message-ID: <585535bf-47d0-178c-706a-3d71bfc31f68@amd.com>
Date:   Thu, 6 Oct 2022 17:08:55 +0530
From:   Ravi Bangoria <ravi.bangoria@....com>
To:     "Liang, Kan" <kan.liang@...ux.intel.com>, peterz@...radead.org,
        acme@...nel.org
Cc:     jolsa@...nel.org, namhyung@...nel.org, eranian@...gle.com,
        irogers@...gle.com, jmario@...hat.com, leo.yan@...aro.org,
        alisaidi@...zon.com, ak@...ux.intel.com,
        dave.hansen@...ux.intel.com, hpa@...or.com, mingo@...hat.com,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        tglx@...utronix.de, bp@...en8.de, x86@...nel.org,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        sandipan.das@....com, ananth.narayan@....com, kim.phillips@....com,
        santosh.shukla@....com, kajoljain <kjain@...ux.ibm.com>,
        Ravi Bangoria <ravi.bangoria@....com>
Subject: Re: [PATCH v3 01/15] perf/mem: Introduce
 PERF_MEM_LVLNUM_{EXTN_MEM|IO}

On 03-Oct-22 6:45 PM, Liang, Kan wrote:
> 
> 
> On 2022-10-01 2:37 a.m., Ravi Bangoria wrote:
>> 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@....com>
>>>>>> ---
>>>>>>  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.
>>
>>
>> From 5deb2055e2b5b0a61403f2d5f4e5a784b14a65e3 Mon Sep 17 00:00:00 2001
>> From: Ravi Bangoria <ravi.bangoria@....com>
>> Date: Sat, 1 Oct 2022 11:37:05 +0530
>> Subject: [PATCH] perf/mem: Rename PERF_MEM_LVLNUM_EXTN_MEM to
>>  PERF_MEM_LVLNUM_CXL
>>
>> PERF_MEM_LVLNUM_EXTN_MEM was introduced to cover CXL devices but it's
>> bit ambiguous name and also not generic enough to cover cxl.cache and
>> cxl.io devices. Rename it to PERF_MEM_LVLNUM_CXL to be more specific.
> 
> Looks good to me.
> 
> Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>

Thanks Kan.

Peter, can you please include this patch along with the series?

Arnaldo, I'll respin tool side of patches with this change.

Thanks,
Ravi