feat: adds gpu usages stat in the toolbar (#36)

* feat: adds gpu usages stat in the toolbar

Applications/LLMEval/ViewModels/DeviceStat.swift

@@ -0,0 +1,42 @@
+import Foundation
+import LLM
+import MLX
+
+@Observable
+class DeviceStat {
+    var gpuUsage = GPU.snapshot()
+    private var initialGPUSnapshot = GPU.snapshot()
+    private var timer: Timer?
+
+    init() {
+        startTimer()
+    }
+
+    deinit {
+        stopTimer()
+    }
+
+    private func startTimer() {
+        timer?.invalidate()
+        timer = Timer.scheduledTimer(withTimeInterval: 2.0, repeats: true) { [weak self] _ in
+            self?.updateStats()
+        }
+    }
+
+    private func stopTimer() {
+        timer?.invalidate()
+        timer = nil
+    }
+
+    private func updateStats() {
+        updateGPUUsages()
+    }
+
+    private func updateGPUUsages() {
+        let gpuSnapshotDelta = initialGPUSnapshot.delta(GPU.snapshot())
+        DispatchQueue.main.async { [weak self] in
+            self?.gpuUsage = gpuSnapshotDelta
+        }
+    }
+
+}