Re: [Patch v1 04/10] perf/x86: add memory profiling via PEBS Load Latency

Peter Zijlstra
2012-10-29T15:38:51Z

On Mon, 2012-10-29 at 16:15 +0100, Stephane Eranian wrote:
> + fll = event->hw.flags & PERF_X86_EVENT_PEBS_LDLAT;
> +
> perf_sample_data_init(&data, 0, event->hw.last_period);
>
> + data.period = event->hw.last_period;
> + sample_type = event->attr.sample_type;
> +
> + /*
> + * if PEBS-LL or PreciseStore
> + */
> + if (fll) {
> + if (sample_type & PERF_SAMPLE_ADDR)
> + data.addr = pebs->dla;
> +
> + /*
> + * Use latency for cost (only avail with PEBS-LL)
> + */
> + if (fll && (sample_type & PERF_SAMPLE_COST))
> + data.cost = pebs->lat;
> +
> + /*
> + * data.dsrc encodes the data source
> + */
> + if (sample_type & PERF_SAMPLE_DSRC) {
> + if (fll)
> + data.dsrc.val = load_latency_data(pebs->dse);
> + }
> + }

Why does fl1 exist? the above looks really convoluted, all fl1 checks
inside are pointless. Also 'fl1' is a bizarre name, 'pebs_ll' would be a
better name I guess.

What's wrong with:

if (event->hw.flags & PERF_X86_EVENT_PEBS_LDLAT) {
if (sample_type & PERF_SAMPLE_ADDR)
data.addr = pebs->dla;

if (sample_type & PERF_SAMPLE_COST)
data.cost = perf->lat;

if (sample_type & PERF_SAMPLE_DSRC)
data.dsrc.val = load_latency_data(pebs->dse);
}