feat(ios): implemented CPU tracking

README.md

@@ -107,7 +107,6 @@ No additional steps for android are required, except when using the new react na
 
 ## Caveats
 
-- 🤖 Currently android only, iOS support will be added shortly
 - By default, no CPU usage will be tracked, as tracking adds a little overhead. Pass `true` to the `.start` function to track CPU as well.
 - The FPS reported may not match 100% from what you see in the "Perf Monitor". However, the values are really close to each other and convey the same information.
   - Technically, this is due to the fact that we only "refresh" the FPS every 500ms in the native impl (so does the "Perf Monitor"). And the `react-native-performance-stats` may started tracking at another point in time than the "Perf Monitor", thus they refresh at different times.

ios/PerformanceStats/PerformanceStats.mm

@@ -12,7 +12,7 @@
 
 // NOTICE: Mainly copied from here: https://github.com/facebook/react-native/blob/main/React/CoreModules/RCTPerfMonitor.mm
 
-
+#pragma Resource usage methods
 static vm_size_t RCTGetResidentMemorySize(void)
 {
   vm_size_t memoryUsageInByte = 0;
@@ -25,6 +25,71 @@ static vm_size_t RCTGetResidentMemorySize(void)
   return memoryUsageInByte;
 }
 
+// https://stackoverflow.com/a/8382889/3668241
+float cpu_usage()
+{
+    kern_return_t kr;
+    task_info_data_t tinfo;
+    mach_msg_type_number_t task_info_count;
+
+    task_info_count = TASK_INFO_MAX;
+    kr = task_info(mach_task_self(), TASK_BASIC_INFO, (task_info_t)tinfo, &task_info_count);
+    if (kr != KERN_SUCCESS) {
+        return -1;
+    }
+
+    task_basic_info_t      basic_info;
+    thread_array_t         thread_list;
+    mach_msg_type_number_t thread_count;
+
+    thread_info_data_t     thinfo;
+    mach_msg_type_number_t thread_info_count;
+
+    thread_basic_info_t basic_info_th;
+    uint32_t stat_thread = 0; // Mach threads
+
+    basic_info = (task_basic_info_t)tinfo;
+
+    // get threads in the task
+    kr = task_threads(mach_task_self(), &thread_list, &thread_count);
+    if (kr != KERN_SUCCESS) {
+        return -1;
+    }
+    if (thread_count > 0)
+        stat_thread += thread_count;
+
+    long tot_sec = 0;
+    long tot_usec = 0;
+    float tot_cpu = 0;
+    int j;
+
+    for (j = 0; j < (int)thread_count; j++)
+    {
+        thread_info_count = THREAD_INFO_MAX;
+        kr = thread_info(thread_list[j], THREAD_BASIC_INFO,
+                         (thread_info_t)thinfo, &thread_info_count);
+        if (kr != KERN_SUCCESS) {
+            return -1;
+        }
+
+        basic_info_th = (thread_basic_info_t)thinfo;
+
+        if (!(basic_info_th->flags & TH_FLAGS_IDLE)) {
+            tot_sec = tot_sec + basic_info_th->user_time.seconds + basic_info_th->system_time.seconds;
+            tot_usec = tot_usec + basic_info_th->user_time.microseconds + basic_info_th->system_time.microseconds;
+            tot_cpu = tot_cpu + basic_info_th->cpu_usage / (float)TH_USAGE_SCALE * 100.0;
+        }
+
+    } // for each thread
+
+    kr = vm_deallocate(mach_task_self(), (vm_offset_t)thread_list, thread_count * sizeof(thread_t));
+    assert(kr == KERN_SUCCESS);
+
+    return tot_cpu;
+}
+
+#pragma Module implementation
+
 @implementation PerformanceStats {
     bool _isRunning;
 
@@ -35,8 +100,6 @@ @implementation PerformanceStats {
     CADisplayLink *_jsDisplayLink;
 }
 
-//@synthesize bridge = _bridge;
-
 RCT_EXPORT_MODULE(PerformanceStats)
 
 + (BOOL)requiresMainQueueSetup
@@ -54,7 +117,7 @@ - (dispatch_queue_t)methodQueue
   return @[ @"performanceStatsUpdate" ];
 }
 
-- (void)updateStats
+- (void)updateStats:(bool)withCPU
 {
     // View count
     NSDictionary<NSNumber *, UIView *> *views = [self.bridge.uiManager valueForKey:@"viewRegistry"];
@@ -68,10 +131,15 @@ - (void)updateStats
 
     // Memory
     double mem = (double)RCTGetResidentMemorySize() / 1024 / 1024;
+    float cpu = 0;
+    if (withCPU) {
+        cpu = cpu_usage();
+    }
 
     [self sendEventWithName:@"performanceStatsUpdate" body:@{
         @"jsFps": [NSNumber numberWithUnsignedInteger:_jsFPSTracker.FPS],
         @"uiFps": [NSNumber numberWithUnsignedInteger:_uiFPSTracker.FPS],
+        @"usedCpu": [NSNumber numberWithFloat:cpu],
         @"usedRam": [NSNumber numberWithDouble:mem],
         @"viewCount": [NSNumber numberWithUnsignedInteger:viewCount],
         @"visibleViewCount": [NSNumber numberWithUnsignedInteger:visibleViewCount]
@@ -81,7 +149,7 @@ - (void)updateStats
     dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
       __strong __typeof__(weakSelf) strongSelf = weakSelf;
       if (strongSelf && strongSelf->_isRunning) {
-        [strongSelf updateStats];
+        [strongSelf updateStats:withCPU];
       }
     });
 }
@@ -98,7 +166,7 @@ - (void)threadUpdate:(CADisplayLink *)displayLink
     _uiFPSTracker= [[FPSTracker alloc] init];
     _jsFPSTracker= [[FPSTracker alloc] init];
 
-    [self updateStats];
+    [self updateStats:withCpu];
 
     // Get FPS for UI Thread
     _uiDisplayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(threadUpdate:)];