perf tools: Support PERF_SAMPLE_WEIGHT_STRUCT

The new sample type, PERF_SAMPLE_WEIGHT_STRUCT, is an alternative of the
PERF_SAMPLE_WEIGHT sample type. Users can apply either the
PERF_SAMPLE_WEIGHT sample type or the PERF_SAMPLE_WEIGHT_STRUCT sample
type to retrieve the sample weight, but they cannot apply both sample
types simultaneously.

The new sample type shares the same space as the PERF_SAMPLE_WEIGHT
sample type. The lower 32 bits are exactly the same for both sample
type. The higher 32 bits may be different for different architecture.

Add arch specific arch_evsel__set_sample_weight() to set the new sample
type for X86. Only store the lower 32 bits for the sample->weight if the
new sample type is applied. In practice, no memory access could last
than 4G cycles. No data will be lost.

If the kernel doesn't support the new sample type. Fall back to the
PERF_SAMPLE_WEIGHT sample type.

There is no impact for other architectures.

Committer notes:

Fixup related to PERF_SAMPLE_CODE_PAGE_SIZE, present in acme/perf/core
but not upstream yet.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/1612296553-21962-6-git-send-email-kan.liang@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 24 insertions, 4 deletions

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index a8ce6b2ebd61..fa49d15edc35 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1014,6 +1014,11 @@ struct evsel_config_term *__evsel__get_config_term(struct evsel *evsel, enum evs
 	return found_term;
 }
 
+void __weak arch_evsel__set_sample_weight(struct evsel *evsel)
+{
+	evsel__set_sample_bit(evsel, WEIGHT);
+}
+
 /*
  * The enable_on_exec/disabled value strategy:
  *
@@ -1168,7 +1173,7 @@ void evsel__config(struct evsel *evsel, struct record_opts *opts,
 	}
 
 	if (opts->sample_weight)
-		evsel__set_sample_bit(evsel, WEIGHT);
+		arch_evsel__set_sample_weight(evsel);
 
 	attr->task     = track;
 	attr->mmap     = track;
@@ -1743,6 +1748,10 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 	}
 
 fallback_missing_features:
+	if (perf_missing_features.weight_struct) {
+		evsel__set_sample_bit(evsel, WEIGHT);
+		evsel__reset_sample_bit(evsel, WEIGHT_STRUCT);
+	}
 	if (perf_missing_features.clockid_wrong)
 		evsel->core.attr.clockid = CLOCK_MONOTONIC; /* should always work */
 	if (perf_missing_features.clockid) {
@@ -1883,7 +1892,12 @@ try_fallback:
 	 * Must probe features in the order they were added to the
 	 * perf_event_attr interface.
 	 */
-	if (!perf_missing_features.code_page_size &&
+	if (!perf_missing_features.weight_struct &&
+	    (evsel->core.attr.sample_type & PERF_SAMPLE_WEIGHT_STRUCT)) {
+		perf_missing_features.weight_struct = true;
+		pr_debug2("switching off weight struct support\n");
+		goto fallback_missing_features;
+	} else if (!perf_missing_features.code_page_size &&
 	    (evsel->core.attr.sample_type & PERF_SAMPLE_CODE_PAGE_SIZE)) {
 		perf_missing_features.code_page_size = true;
 		pr_debug2_peo("Kernel has no PERF_SAMPLE_CODE_PAGE_SIZE support, bailing out\n");
@@ -2331,9 +2345,15 @@ int evsel__parse_sample(struct evsel *evsel, union perf_event *event,
 		}
 	}
 
-	if (type & PERF_SAMPLE_WEIGHT) {
+	if (type & PERF_SAMPLE_WEIGHT_TYPE) {
+		union perf_sample_weight weight;
+
 		OVERFLOW_CHECK_u64(array);
-		data->weight = *array;
+		weight.full = *array;
+		if (type & PERF_SAMPLE_WEIGHT)
+			data->weight = weight.full;
+		else
+			data->weight = weight.var1_dw;
 		array++;
 	}