libbpf-tools/softirqs: Add -c/--cpu option to filter cpu

tools/softirqs.py supports `-c/--cpu` otption to filter cpu, It's reasonable to support a same otption for libbpf-tools/softirqs. Reported-by: Tang Yizhou <[email protected]> Signed-off-by: Dantezy <[email protected]>
iovisor · Sep 30, 2024 · d6eb263 · d6eb263
1 parent 9f3d0df
commit d6eb263
Show file tree

Hide file tree

Showing 2 changed files with 29 additions and 2 deletions.
diff --git a/libbpf-tools/softirqs.bpf.c b/libbpf-tools/softirqs.bpf.c
@@ -9,6 +9,7 @@
 
 const volatile bool targ_dist = false;
 const volatile bool targ_ns = false;
+const volatile int targ_cpu = -1;
 
 struct {
 	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
@@ -21,8 +22,18 @@ __u64 counts[NR_SOFTIRQS] = {};
 __u64 time[NR_SOFTIRQS] = {};
 struct hist hists[NR_SOFTIRQS] = {};
 
+static bool is_target_cpu() {
+        if (targ_cpu < 0)
+	        return true;
+
+	return bpf_get_smp_processor_id() == (u32)targ_cpu;
+}
+
 static int handle_entry(unsigned int vec_nr)
 {
+        if (!is_target_cpu())
+	        return 0;
+
 	u64 ts = bpf_ktime_get_ns();
 	u32 key = 0;
 
@@ -32,11 +43,14 @@ static int handle_entry(unsigned int vec_nr)
 
 static int handle_exit(unsigned int vec_nr)
 {
+        if (!is_target_cpu())
+	        return 0;
+
 	u64 delta, *tsp;
 	u32 key = 0;
 
-	if (vec_nr >= NR_SOFTIRQS)
-		return 0;
+	vec_nr &= 0xf;  // to avoid compiler opti make verifier error
+
 	tsp = bpf_map_lookup_elem(&start, &key);
 	if (!tsp)
 		return 0;

diff --git a/libbpf-tools/softirqs.c b/libbpf-tools/softirqs.c
@@ -24,10 +24,12 @@ struct env {
 	int times;
 	bool timestamp;
 	bool verbose;
+        int targ_cpu;
 } env = {
 	.interval = 99999999,
 	.times = 99999999,
 	.count = false,
+	.targ_cpu = -1,
 };
 
 static volatile bool exiting;
@@ -43,6 +45,7 @@ const char argp_program_doc[] =
 "EXAMPLES:\n"
 "    softirqs            # sum soft irq event time\n"
 "    softirqs -d         # show soft irq event time as histograms\n"
+"    softirqs -c 1         # show soft irq event time on cpu 1\n"
 "    softirqs 1 10       # print 1 second summaries, 10 times\n"
 "    softirqs -NT 1      # 1s summaries, nanoseconds, and timestamps\n";
 
@@ -51,6 +54,7 @@ static const struct argp_option opts[] = {
 	{ "timestamp", 'T', NULL, 0, "Include timestamp on output", 0 },
 	{ "nanoseconds", 'N', NULL, 0, "Output in nanoseconds", 0 },
 	{ "count", 'C', NULL, 0, "Show event counts with timing", 0 },
+	{"cpu", 'c', "CPU", 0, "Trace this cpu only", 0},
 	{ "verbose", 'v', NULL, 0, "Verbose debug output", 0 },
 	{ NULL, 'h', NULL, OPTION_HIDDEN, "Show the full help", 0 },
 	{},
@@ -79,6 +83,14 @@ static error_t parse_arg(int key, char *arg, struct argp_state *state)
 	case 'C':
 		env.count = true;
 		break;
+        case 'c':
+		errno = 0;
+		env.targ_cpu = atoi(arg);
+		if (errno || env.targ_cpu < 0) {
+		        fprintf(stderr, "invalid cpu: %s\n", arg);
+			argp_usage(state);
+		}
+		break;
 	case ARGP_KEY_ARG:
 		errno = 0;
 		if (pos_args == 0) {
@@ -228,6 +240,7 @@ int main(int argc, char **argv)
 	/* initialize global data (filtering options) */
 	obj->rodata->targ_dist = env.distributed;
 	obj->rodata->targ_ns = env.nanoseconds;
+        obj->rodata->targ_cpu = env.targ_cpu;
 
 	err = softirqs_bpf__load(obj);
 	if (err) {