[PATCH v0 2/2] perf record: Add --aux-highorder

[Alexander Shishkin]

Allow requesting high-order AUX allocations from the perf record command
line. Since this operation requires CAP_SYS_ADMIN, adjust the error message
to suggest this as a potential reason of failure.

Signed-off-by: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
---
 tools/include/uapi/linux/perf_event.h | 3 ++-
 tools/perf/builtin-record.c           | 2 ++
 tools/perf/perf.h                     | 1 +
 tools/perf/util/evsel.c               | 9 +++++++++
 4 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
index 7198ddd0c6b1..04726b5729c8 100644
--- a/tools/include/uapi/linux/perf_event.h
+++ b/tools/include/uapi/linux/perf_event.h
@@ -374,7 +374,8 @@ struct perf_event_attr {
 				namespaces     :  1, /* include namespaces data */
 				ksymbol        :  1, /* include ksymbol events */
 				bpf_event      :  1, /* include bpf events */
-				__reserved_1   : 33;
+				aux_highorder  :  1, /* use high order allocations for AUX data */
+				__reserved_1   : 32;
 
 	union {
 		__u32		wakeup_events;	  /* wakeup every n events */
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 3fdfbaebd95e..9f8d5eba24a8 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1929,6 +1929,8 @@ static struct option __record_options[] = {
 	parse_clockid),
 	OPT_STRING_OPTARG('S', "snapshot", &record.opts.auxtrace_snapshot_opts,
 			  "opts", "AUX area tracing Snapshot Mode", ""),
+	OPT_BOOLEAN(0, "aux-highorder", &record.opts.aux_highorder,
+		    "Use high-order allocation for AUX buffers"),
 	OPT_UINTEGER(0, "proc-map-timeout", &proc_map_timeout,
 			"per thread proc mmap processing timeout in ms"),
 	OPT_BOOLEAN(0, "namespaces", &record.opts.record_namespaces,
diff --git a/tools/perf/perf.h b/tools/perf/perf.h
index b120e547ddc7..42f1fa5faeed 100644
--- a/tools/perf/perf.h
+++ b/tools/perf/perf.h
@@ -67,6 +67,7 @@ struct record_opts {
 	bool	     strict_freq;
 	bool	     sample_id;
 	bool	     bpf_event;
+	bool	     aux_highorder;
 	unsigned int freq;
 	unsigned int mmap_pages;
 	unsigned int auxtrace_mmap_pages;
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 684c893ca6bc..3f4dc8f79d2f 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1098,6 +1098,9 @@ void perf_evsel__config(struct perf_evsel *evsel, struct record_opts *opts,
 	if (evsel->own_cpus || evsel->unit)
 		evsel->attr.read_format |= PERF_FORMAT_ID;
 
+	if (opts->aux_highorder)
+		attr->aux_highorder = 1;
+
 	/*
 	 * Apply event specific term settings,
 	 * it overloads any global configuration.
@@ -1657,6 +1660,7 @@ int perf_event_attr__fprintf(FILE *fp, struct perf_event_attr *attr,
 	PRINT_ATTRf(namespaces, p_unsigned);
 	PRINT_ATTRf(ksymbol, p_unsigned);
 	PRINT_ATTRf(bpf_event, p_unsigned);
+	PRINT_ATTRf(aux_highorder, p_unsigned);
 
 	PRINT_ATTRn("{ wakeup_events, wakeup_watermark }", wakeup_events, p_unsigned);
 	PRINT_ATTRf(bp_type, p_unsigned);
@@ -2891,6 +2895,11 @@ int perf_evsel__open_strerror(struct perf_evsel *evsel, struct target *target,
 				"No permission to enable %s event.\n\n",
 				perf_evsel__name(evsel));
 
+		if (evsel->attr.aux_highorder)
+			printed += scnprintf(msg + printed, size - printed,
+					     "Using --aux-highorder may not be possible with your privilege level,\n"
+					     "which requires CAP_SYS_ADMIN capability. Consider using sudo.\n\n");
+
 		return scnprintf(msg + printed, size - printed,
 		 "You may not have permission to collect %sstats.\n\n"
 		 "Consider tweaking /proc/sys/kernel/perf_event_paranoid,\n"
-- 
2.20.1