On Tue, Jan 19, 2021 at 12:38:22PM -0800, kan.li...@linux.intel.com wrote:
> @@ -1577,9 +1668,20 @@ static void setup_pebs_adaptive_sample_data(struct
> perf_event *event,
> }
>
> if (format_size & PEBS_DATACFG_MEMINFO) {
> + if (sample_type & PERF_SAMPLE_WEIGHT) {
> + u64 weight = meminfo->latency;
> +
> + if (x86_pmu.flags & PMU_FL_INSTR_LATENCY)
> + weight >>= PEBS_CACHE_LATENCY_OFFSET;
> + data->weight = weight & PEBS_LATENCY_MASK ?:
> intel_get_tsx_weight(meminfo->tsx_tuning);
> + }
> +
> + if (sample_type & PERF_SAMPLE_WEIGHT_EXT) {
> + data->weight_ext.val = 0;
> + if (x86_pmu.flags & PMU_FL_INSTR_LATENCY)
> + data->weight_ext.instr_latency =
> meminfo->latency & PEBS_LATENCY_MASK;
> + }
>
> if (sample_type & PERF_SAMPLE_DATA_SRC)
> data->data_src.val = get_data_src(event, meminfo->aux);
Talk to me about that SAMPLE_WEIGHT stuff.... I'm not liking it.
Sure you want multiple dimensions, but urgh.
Also, afaict, as proposed you're wasting 80/128 bits. That is, all data
you want to export fits in a single u64 and yet you're using two, which
is mighty daft.
Sure, pebs::lat / pebs_meminfo::latency is defined as a u64, but you
can't tell me that that is ever actually more than 4G cycles. Even the
TSX block latency is u32.
So how about defining SAMPLE_WEIGHT_STRUCT which uses the exact same
data as SAMPLE_WEIGHT but unions it with a struct. I'm not sure if we
want:
union sample_weight {
u64 weight;
struct {
u32 low_dword;
u32 high_dword;
};
/* or */
struct {
u32 low_dword;
u16 high_word;
u16 higher_word;
};
};
Then have the core code enforce SAMPLE_WEIGHT ^ SAMPLE_WEIGHT_STRUCT and
make the existing code never set the high dword.
Hmmm?
