Re: [PATCH v5 2/5] perf: Add SNOOP_PEER flag to perf mem data struct

[Leo Yan]

On Fri, Apr 08, 2022 at 07:53:41PM +0000, Ali Saidi wrote:
> Add a flag to the perf mem data struct to signal that a request caused a
> cache-to-cache transfer of a line from a peer of the requestor and
> wasn't sourced from a lower cache level.  The line being moved from one
> peer cache to another has latency and performance implications. On Arm64
> Neoverse systems the data source can indicate a cache-to-cache transfer
> but not if the line is dirty or clean, so instead of overloading HITM
> define a new flag that indicates this type of transfer.
> 
> Signed-off-by: Ali Saidi <alisaidi@xxxxxxxxxx>

The patch looks good to me:
Reviewed-by: Leo Yan <leo.yan@xxxxxxxxxx>

Sine this is a common flag, it's better if x86 or PowerPC maintainers
could take a look for this new snooping type.  Thanks!

Leo

> ---
>  include/uapi/linux/perf_event.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index 82858b697c05..c9e58c79f3e5 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -1308,7 +1308,7 @@ union perf_mem_data_src {
>  #define PERF_MEM_SNOOP_SHIFT	19
>  
>  #define PERF_MEM_SNOOPX_FWD	0x01 /* forward */
> -/* 1 free */
> +#define PERF_MEM_SNOOPX_PEER	0x02 /* xfer from peer */
>  #define PERF_MEM_SNOOPX_SHIFT  38
>  
>  /* locked instruction */
> -- 
> 2.32.0
>