perf: Extract building cache level for a CPU into separate function

build_caches() builds the complete cache topology of the system by
iterating over all CPU, building and comparing cache levels of each CPU,
keeping only the unique ones at the end.

Extract the unit that build the cache levels for a single CPU into a
separate function. Expose this function, and the MAX_CACHE_LVL value to
be used elsewhere in perf too.

Signed-off-by: K Prateek Nayak <[e-mail]>
Acked-by: Ian Rogers <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Ananth Narayan <[e-mail]>
Cc: Gautham Shenoy <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Ravi Bangoria <[e-mail]>
Cc: Sandipan Das <[e-mail]>
Cc: Stephane Eranian <[e-mail]>
Cc: Wen Pu <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/header.c

···
 	fprintf(out, "L%d %-15s %8s [%s]\n", c->level, c->type, c->size, c->map);
 }
 
-#define MAX_CACHE_LVL 4
+/*
+ * Build caches levels for a particular CPU from the data in
+ * /sys/devices/system/cpu/cpu<cpu>/cache/
+ * The cache level data is stored in caches[] from index at
+ * *cntp.
+ */
+int build_caches_for_cpu(u32 cpu, struct cpu_cache_level caches[], u32 *cntp)
+{
+	u16 level;
+
+	for (level = 0; level < MAX_CACHE_LVL; level++) {
+		struct cpu_cache_level c;
+		int err;
+		u32 i;
+
+		err = cpu_cache_level__read(&c, cpu, level);
+		if (err < 0)
+			return err;
+
+		if (err == 1)
+			break;
+
+		for (i = 0; i < *cntp; i++) {
+			if (cpu_cache_level__cmp(&c, &caches[i]))
+				break;
+		}
+
+		if (i == *cntp) {
+			caches[*cntp] = c;
+			*cntp = *cntp + 1;
+		} else
+			cpu_cache_level__free(&c);
+	}
+
+	return 0;
+}
 
 static int build_caches(struct cpu_cache_level caches[], u32 *cntp)
 {
-	u32 i, cnt = 0;
-	u32 nr, cpu;
-	u16 level;
+	u32 nr, cpu, cnt = 0;
 
 	nr = cpu__max_cpu().cpu;
 
 	for (cpu = 0; cpu < nr; cpu++) {
-		for (level = 0; level < MAX_CACHE_LVL; level++) {
-			struct cpu_cache_level c;
-			int err;
+		int ret = build_caches_for_cpu(cpu, caches, &cnt);
 
-			err = cpu_cache_level__read(&c, cpu, level);
-			if (err < 0)
-				return err;
-
-			if (err == 1)
-				break;
-
-			for (i = 0; i < cnt; i++) {
-				if (cpu_cache_level__cmp(&c, &caches[i]))
-					break;
-			}
-
-			if (i == cnt)
-				caches[cnt++] = c;
-			else
-				cpu_cache_level__free(&c);
-		}
+		if (ret)
+			return ret;
 	}
 	*cntp = cnt;
 	return 0;

tools/perf/util/header.h

···
 int write_padded(struct feat_fd *fd, const void *bf,
 		 size_t count, size_t count_aligned);
 
+#define MAX_CACHE_LVL 4
+
 int is_cpu_online(unsigned int cpu);
+int build_caches_for_cpu(u32 cpu, struct cpu_cache_level caches[], u32 *cntp);
+
 /*
  * arch specific callback
  */