basic/procfs-util: add procfs_cpu_get_ticks()

src/basic/procfs-util.c

@@ -171,6 +171,39 @@ int procfs_cpu_get_usage(nsec_t *ret) {
         return 0;
 }
 
+int procfs_cpu_get_ticks(ProcfsCpuTicks *ret) {
+        _cleanup_free_ char *first_line = NULL;
+        int r;
+
+        assert(ret);
+
+        r = read_one_line_file("/proc/stat", &first_line);
+        if (r < 0)
+                return r;
+
+        const char *p = first_word(first_line, "cpu");
+        if (!p)
+                return -EINVAL;
+
+        /* All eight fields exist on any kernel we support: iowait was added in 2.5.41, steal in 2.6.11.
+         * "guest" and "guest_nice" are not returned, the kernel already includes them in "user" and
+         * "nice". */
+        ProcfsCpuTicks t;
+        if (sscanf(p, "%"SCNu64" %"SCNu64" %"SCNu64" %"SCNu64" %"SCNu64" %"SCNu64" %"SCNu64" %"SCNu64,
+                   &t.user,
+                   &t.nice,
+                   &t.system,
+                   &t.idle,
+                   &t.iowait,
+                   &t.irq,
+                   &t.softirq,
+                   &t.steal) < 8)
+                return -EINVAL;
+
+        *ret = t;
+        return 0;
+}
+
 int convert_meminfo_value_to_uint64_bytes(const char *s, uint64_t *ret) {
         _cleanup_free_ char *w = NULL;
         uint64_t v;

src/basic/procfs-util.h

@@ -11,6 +11,19 @@ int procfs_tasks_get_current(uint64_t *ret);
 
 int procfs_cpu_get_usage(nsec_t *ret);
 
+typedef struct ProcfsCpuTicks {
+        uint64_t user;
+        uint64_t nice;
+        uint64_t system;
+        uint64_t idle;
+        uint64_t iowait;
+        uint64_t irq;
+        uint64_t softirq;
+        uint64_t steal;
+} ProcfsCpuTicks;
+
+int procfs_cpu_get_ticks(ProcfsCpuTicks *ret);
+
 int procfs_memory_get(uint64_t *ret_total, uint64_t *ret_used);
 static inline int procfs_memory_get_used(uint64_t *ret) {
         return procfs_memory_get(NULL, ret);

src/test/test-procfs-util.c

@@ -18,6 +18,14 @@ int main(int argc, char *argv[]) {
         ASSERT_OK(procfs_cpu_get_usage(&nsec));
         log_info("Current system CPU time: %s", FORMAT_TIMESPAN(nsec/NSEC_PER_USEC, 1));
 
+        ProcfsCpuTicks ticks;
+        ASSERT_OK(procfs_cpu_get_ticks(&ticks));
+        log_info("Current CPU ticks: user=%" PRIu64 " nice=%" PRIu64 " system=%" PRIu64 " idle=%" PRIu64
+                 " iowait=%" PRIu64 " irq=%" PRIu64 " softirq=%" PRIu64 " steal=%" PRIu64,
+                 ticks.user, ticks.nice, ticks.system, ticks.idle,
+                 ticks.iowait, ticks.irq, ticks.softirq, ticks.steal);
+        ASSERT_GT(ticks.idle, 0U);
+
         ASSERT_OK(procfs_memory_get_used(&v));
         log_info("Current memory usage: %s", FORMAT_BYTES(v));