On Wed, Jun 07, 2017 at 04:22:24PM -0700, Andi Kleen wrote:

> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index b1c0b187acfe..95daade294d7 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -931,14 +931,18 @@ union perf_mem_data_src {
>                       mem_snoop:5,    /* snoop mode */
>                       mem_lock:2,     /* lock instr */
>                       mem_dtlb:7,     /* tlb access */
> -                     mem_rsvd:31;
> +                     mem_lvlx:8,     /* memory hierarchy level, ext */
> +                     mem_snoopx:2,   /* snoop mode, ext */
> +                     mem_rsvd:21;
>       };
>  };
>  #elif defined(__BIG_ENDIAN_BITFIELD)
>  union perf_mem_data_src {
>       __u64 val;
>       struct {
> -             __u64   mem_rsvd:31,
> +             __u64   mem_rsvd:21,
> +                     mem_snoopx:2,   /* snoop mode, ext */
> +                     mem_lvlx:8,     /* memory hierarchy level, ext */
>                       mem_dtlb:7,     /* tlb access */
>                       mem_lock:2,     /* lock instr */
>                       mem_snoop:5,    /* snoop mode */

So one thing we could do is add a mem_hops field and always set that,
even for the old stuff. The old stuff will not know about that field and
ignore the bits, but new stuff will then not need as many LVL bits.

Of course, we then get into the problem of how many bits of hops we
need.. Power guys ?

> @@ -975,6 +979,16 @@ union perf_mem_data_src {
>  #define PERF_MEM_LVL_UNC     0x2000 /* Uncached memory */
>  #define PERF_MEM_LVL_SHIFT   5
>  
> +#define PERF_MEM_LVLX_L4     0x01 /* L4 */
> +#define PERF_MEM_LVLX_REM_L4    0x02 /* Remote L4 */
> +#define PERF_MEM_LVLX_REM_RAM        0x04 /* Remote Ram, unknown hops */
> +#define PERF_MEM_LVLX_PMEM   0x08 /* Persistent Memory */
> +#define PERF_MEM_LVLX_REM_PMEM       0x10 /* Remote Persistent Memory */
> +#define PERF_MEM_LVLX_REM_NA 0x20 /* Remote N/A level */

Still wondering what the point of REM_NA is.. can you explain?

> +/* 2 free */
> +
> +#define PERF_MEM_LVLX_SHIFT  33
> +
>  /* snoop mode */
>  #define PERF_MEM_SNOOP_NA    0x01 /* not available */
>  #define PERF_MEM_SNOOP_NONE  0x02 /* no snoop */
> @@ -983,6 +997,10 @@ union perf_mem_data_src {
>  #define PERF_MEM_SNOOP_HITM  0x10 /* snoop hit modified */
>  #define PERF_MEM_SNOOP_SHIFT 19
>  
> +#define PERF_MEM_SNOOPX_FWD  0x01 /* forward */
> +/* 1 free */
> +#define PERF_MEM_SNOOPX_SHIFT        41
> +
>  /* locked instruction */
>  #define PERF_MEM_LOCK_NA     0x01 /* not available */
>  #define PERF_MEM_LOCK_LOCKED 0x02 /* locked transaction */
> -- 
> 2.9.4
> 

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