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

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Message-ID: <d428b526-a592-2ea5-dad8-d6eae72eb118@linux.intel.com>
Date:   Mon, 3 Oct 2022 09:15:52 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Ravi Bangoria <ravi.bangoria@....com>,
        kajoljain <kjain@...ux.ibm.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
Subject: Re: [PATCH v3 01/15] perf/mem: Introduce
 PERF_MEM_LVLNUM_{EXTN_MEM|IO}



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

> 
> Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
> ---
>  arch/x86/events/amd/ibs.c       | 2 +-
>  include/uapi/linux/perf_event.h | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
> index 3271735f0070..4cb710efbdd9 100644
> --- a/arch/x86/events/amd/ibs.c
> +++ b/arch/x86/events/amd/ibs.c
> @@ -801,7 +801,7 @@ static void perf_ibs_get_mem_lvl(union ibs_op_data2 *op_data2,
>  	/* Extension Memory */
>  	if (ibs_caps & IBS_CAPS_ZEN4 &&
>  	    ibs_data_src == IBS_DATA_SRC_EXT_EXT_MEM) {
> -		data_src->mem_lvl_num = PERF_MEM_LVLNUM_EXTN_MEM;
> +		data_src->mem_lvl_num = PERF_MEM_LVLNUM_CXL;
>  		if (op_data2->rmt_node) {
>  			data_src->mem_remote = PERF_MEM_REMOTE_REMOTE;
>  			/* IBS doesn't provide Remote socket detail */
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index 85be78e0e7f6..eb1090604d53 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -1337,7 +1337,7 @@ union perf_mem_data_src {
>  #define PERF_MEM_LVLNUM_L3	0x03 /* L3 */
>  #define PERF_MEM_LVLNUM_L4	0x04 /* L4 */
>  /* 5-0x8 available */
> -#define PERF_MEM_LVLNUM_EXTN_MEM 0x09 /* Extension memory */
> +#define PERF_MEM_LVLNUM_CXL	0x09 /* CXL */
>  #define PERF_MEM_LVLNUM_IO	0x0a /* I/O */
>  #define PERF_MEM_LVLNUM_ANY_CACHE 0x0b /* Any cache */
>  #define PERF_MEM_LVLNUM_LFB	0x0c /* LFB */