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

[kajoljain <kjain@linux.ibm.com>]

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@amd.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?

Thanks,
Kajol Jain

> +#define PERF_MEM_LVLNUM_IO	0x0a /* I/O */
>  #define PERF_MEM_LVLNUM_ANY_CACHE 0x0b /* Any cache */
>  #define PERF_MEM_LVLNUM_LFB	0x0c /* LFB */
>  #define PERF_MEM_LVLNUM_RAM	0x0d /* RAM */