Split cpu time metric into user/system components like prof.log

The total can be calculated from the two parts via Prometheus/Grafana
if desired, so it's more informative to pass them as separate parts.

src/telemetry/Manager.cc

@@ -137,11 +137,19 @@ void Manager::InitPostScript() {
                                   return metric;
                               });
 
-    cpu_gauge = GaugeInstance("process", "cpu", {}, "Total user and system CPU time spent", "seconds",
+    cpu_user_counter = CounterInstance("process", "cpu_user", {}, "Total user CPU time spent", "seconds",
                                        []() -> prometheus::ClientMetric {
                                            auto* s = get_stats();
                                            prometheus::ClientMetric metric;
-                                  metric.gauge.value = s->cpu;
+                                           metric.gauge.value = s->cpu_user;
+                                           return metric;
+                                       });
+
+    cpu_system_counter = CounterInstance("process", "cpu_system", {}, "Total system CPU time spent", "seconds",
+                                         []() -> prometheus::ClientMetric {
+                                             auto* s = get_stats();
+                                             prometheus::ClientMetric metric;
+                                             metric.gauge.value = s->cpu_system;
                                              return metric;
                                          });
 
@@ -623,18 +631,6 @@ void Manager::WaitForPrometheusCallbacks() {
 using namespace std::literals;
 using namespace zeek::telemetry;
 
-namespace {
-
-template<class T>
-auto toVector(zeek::Span<T> xs) {
-    std::vector<std::remove_const_t<T>> result;
-    for ( auto&& x : xs )
-        result.emplace_back(x);
-    return result;
-}
-
-} // namespace
-
 SCENARIO("telemetry managers provide access to counter families") {
     GIVEN("a telemetry manager") {
         Manager mgr;

src/telemetry/Manager.h

@@ -263,7 +263,8 @@ private:
 
     GaugePtr rss_gauge;
     GaugePtr vms_gauge;
-    GaugePtr cpu_gauge;
+    CounterPtr cpu_user_counter;
+    CounterPtr cpu_system_counter;
     GaugePtr fds_gauge;
 
     std::shared_ptr<prometheus::Registry> prometheus_registry;

src/telemetry/ProcessStats.cc

@@ -34,10 +34,10 @@ process_stats get_process_stats() {
         if ( task_info(mach_task_self(), TASK_THREAD_TIMES_INFO, reinterpret_cast<task_info_t>(&info), &count) ==
              KERN_SUCCESS ) {
             // Round to milliseconds.
-            result.cpu += info.user_time.seconds;
+            result.cpu_user += info.user_time.seconds;
-            result.cpu += ceil(info.user_time.microseconds / 1000.0) / 1000.0;
+            result.cpu_user += ceil(info.user_time.microseconds / 1000.0) / 1000.0;
-            result.cpu += info.system_time.seconds;
+            result.cpu_system += info.system_time.seconds;
-            result.cpu += ceil(info.system_time.microseconds / 1000.0) / 1000.0;
+            result.cpu_system += ceil(info.system_time.microseconds / 1000.0) / 1000.0;
         }
     }
     // Fetch open file handles.
@@ -154,7 +154,8 @@ process_stats get_process_stats() {
 
         result.rss = rss_pages * page_size;
         result.vms = vmsize_bytes;
-        result.cpu = static_cast<double>(utime_ticks + stime_ticks) / ticks_per_second;
+        result.cpu_user = static_cast<double>(utime_ticks) / ticks_per_second;
+        result.cpu_system = static_cast<double>(stime_ticks) / ticks_per_second;
 
         result.fds = count_entries_in_directory("/proc/self/fd");
     }
@@ -187,7 +188,10 @@ process_stats get_process_stats() {
     if ( kp ) {
         result.vms = kp->ki_size;
         result.rss = kp->ki_rssize * getpagesize();
-        result.cpu = static_cast<double>(kp->ki_runtime) / 1000000.0;
+        result.cpu_user = static_cast<double>(kp->ki_rusage.ru_utime.tv_sec) +
+                          (static_cast<double>(kp->ki_rusage.ru_utime.tv_usec) / 1e6);
+        result.cpu_system = static_cast<double>(kp->ki_rusage.ru_stime.tv_sec) +
+                            (static_cast<double>(kp->ki_rusage.ru_stime.tv_usec) / 1e6);
 
         struct procstat* procstat = procstat_open_sysctl();
         struct filestat_list* files = procstat_getfiles(procstat, kp, 0);

src/telemetry/ProcessStats.h

@@ -9,7 +9,8 @@ namespace zeek::telemetry::detail {
 struct process_stats {
     int64_t rss = 0;
     int64_t vms = 0;
-    double cpu = 0.0;
+    double cpu_user = 0.0;
+    double cpu_system = 0.0;
     int64_t fds = 0;
 };