[PATCH v3 1/5] perf record off-cpu: Add direct off-cpu event

[Howard Chu]

Add direct off-cpu event called "offcpu-time-direct". Add a threshold to
dump direct off-cpu samples, "--off-cpu-thresh". Default value of
--off-cpu-thresh is UULONG_MAX(no direct off-cpu samples), and
--off-cpu-thresh's unit is milliseconds.

Bind fds and sample_id in off_cpu_start()

Note that we add "offcpu-time-direct" event using parse_event(), because we
need to make it no-inherit, otherwise perf_event_open() will fail.

Introduce sample_type_embed, indicating the sample_type of a sample
embedded in BPF output. More discussions in later patches.

Signed-off-by: Howard Chu <howardchu95@xxxxxxxxx>
Suggested-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/perf/builtin-record.c   |  2 ++
 tools/perf/util/bpf_off_cpu.c | 53 ++++++++++++++++++++++++++++++++++-
 tools/perf/util/off_cpu.h     |  1 +
 tools/perf/util/record.h      |  1 +
 4 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index a94516e8c522..708d48d309d6 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -3325,6 +3325,7 @@ static struct record record = {
 		.ctl_fd              = -1,
 		.ctl_fd_ack          = -1,
 		.synth               = PERF_SYNTH_ALL,
+		.off_cpu_thresh      = ULLONG_MAX,
 	},
 	.tool = {
 		.sample		= process_sample_event,
@@ -3557,6 +3558,7 @@ static struct option __record_options[] = {
 			    "write collected trace data into several data files using parallel threads",
 			    record__parse_threads),
 	OPT_BOOLEAN(0, "off-cpu", &record.off_cpu, "Enable off-cpu analysis"),
+	OPT_U64(0, "off-cpu-thresh", &record.opts.off_cpu_thresh, "time threshold(in ms) for dumping off-cpu events"),
 	OPT_END()
 };
 
diff --git a/tools/perf/util/bpf_off_cpu.c b/tools/perf/util/bpf_off_cpu.c
index 6af36142dc5a..905a11c96c5b 100644
--- a/tools/perf/util/bpf_off_cpu.c
+++ b/tools/perf/util/bpf_off_cpu.c
@@ -13,6 +13,7 @@
 #include "util/cgroup.h"
 #include "util/strlist.h"
 #include <bpf/bpf.h>
+#include <internal/xyarray.h>
 
 #include "bpf_skel/off_cpu.skel.h"
 
@@ -45,10 +46,12 @@ static int off_cpu_config(struct evlist *evlist)
 		.size	= sizeof(attr), /* to capture ABI version */
 	};
 	char *evname = strdup(OFFCPU_EVENT);
+	char off_cpu_direct_event[64];
 
 	if (evname == NULL)
 		return -ENOMEM;
 
+	/* off-cpu event in the end */
 	evsel = evsel__new(&attr);
 	if (!evsel) {
 		free(evname);
@@ -65,12 +68,22 @@ static int off_cpu_config(struct evlist *evlist)
 	free(evsel->name);
 	evsel->name = evname;
 
+	/* direct off-cpu event */
+	snprintf(off_cpu_direct_event, sizeof(off_cpu_direct_event), "bpf-output/no-inherit=1,name=%s/", OFFCPU_EVENT_DIRECT);
+	if (parse_event(evlist, off_cpu_direct_event)) {
+		pr_err("Failed to open off-cpu event\n");
+		return -1;
+	}
+
 	return 0;
 }
 
 static void off_cpu_start(void *arg)
 {
 	struct evlist *evlist = arg;
+	struct evsel *evsel;
+	struct perf_cpu pcpu;
+	int i, err;
 
 	/* update task filter for the given workload */
 	if (!skel->bss->has_cpu && !skel->bss->has_task &&
@@ -86,6 +99,27 @@ static void off_cpu_start(void *arg)
 		bpf_map_update_elem(fd, &pid, &val, BPF_ANY);
 	}
 
+	/* sample id and fds in BPF's perf_event_array can only be set after record__open() */
+	evsel = evlist__find_evsel_by_str(evlist, OFFCPU_EVENT_DIRECT);
+	if (evsel == NULL) {
+		pr_err("%s evsel not found\n", OFFCPU_EVENT_DIRECT);
+		return;
+	}
+
+	if (evsel->core.id)
+		skel->bss->sample_id = evsel->core.id[0];
+
+	perf_cpu_map__for_each_cpu(pcpu, i, evsel->core.cpus) {
+		err = bpf_map__update_elem(skel->maps.offcpu_output,
+					   &pcpu.cpu, sizeof(__u32),
+					   xyarray__entry(evsel->core.fd, pcpu.cpu, 0),
+					   sizeof(__u32), BPF_ANY);
+		if (err) {
+			pr_err("Failed to update perf event map for direct off-cpu dumping\n");
+			return;
+		}
+	}
+
 	skel->bss->enabled = 1;
 }
 
@@ -130,14 +164,24 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
 {
 	int err, fd, i;
 	int ncpus = 1, ntasks = 1, ncgrps = 1;
+	__u64 offcpu_thresh;
 	struct strlist *pid_slist = NULL;
 	struct str_node *pos;
+	struct evsel *evsel;
 
 	if (off_cpu_config(evlist) < 0) {
 		pr_err("Failed to config off-cpu BPF event\n");
 		return -1;
 	}
 
+	evsel = evlist__find_evsel_by_str(evlist, OFFCPU_EVENT_DIRECT);
+	if (evsel == NULL) {
+		pr_err("%s evsel not found\n", OFFCPU_EVENT_DIRECT);
+		return -1 ;
+	}
+
+	evsel->sample_type_embed = OFFCPU_SAMPLE_TYPES;
+
 	skel = off_cpu_bpf__open();
 	if (!skel) {
 		pr_err("Failed to open off-cpu BPF skeleton\n");
@@ -250,7 +294,6 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
 	}
 
 	if (evlist__first(evlist)->cgrp) {
-		struct evsel *evsel;
 		u8 val = 1;
 
 		skel->bss->has_cgroup = 1;
@@ -272,6 +315,14 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
 		}
 	}
 
+	offcpu_thresh = opts->off_cpu_thresh;
+
+	if (opts->off_cpu_thresh != ULLONG_MAX)
+		offcpu_thresh = opts->off_cpu_thresh * 1000000; /* off-cpu-thresh is in ms */
+
+	skel->bss->offcpu_thresh = offcpu_thresh;
+	skel->bss->sample_type   = OFFCPU_SAMPLE_TYPES;
+
 	err = off_cpu_bpf__attach(skel);
 	if (err) {
 		pr_err("Failed to attach off-cpu BPF skeleton\n");
diff --git a/tools/perf/util/off_cpu.h b/tools/perf/util/off_cpu.h
index 2dd67c60f211..a349f8e300e0 100644
--- a/tools/perf/util/off_cpu.h
+++ b/tools/perf/util/off_cpu.h
@@ -9,6 +9,7 @@ struct perf_session;
 struct record_opts;
 
 #define OFFCPU_EVENT  "offcpu-time"
+#define OFFCPU_EVENT_DIRECT  "offcpu-time-direct"
 
 #define OFFCPU_SAMPLE_TYPES  (PERF_SAMPLE_IDENTIFIER | PERF_SAMPLE_IP | \
 			      PERF_SAMPLE_TID | PERF_SAMPLE_TIME | \
diff --git a/tools/perf/util/record.h b/tools/perf/util/record.h
index a6566134e09e..3c11416e6627 100644
--- a/tools/perf/util/record.h
+++ b/tools/perf/util/record.h
@@ -79,6 +79,7 @@ struct record_opts {
 	int	      synth;
 	int	      threads_spec;
 	const char    *threads_user_spec;
+	u64	      off_cpu_thresh;
 };
 
 extern const char * const *record_usage;
-- 
2.45.2