Cache localhost hostname to eliminate Tab key sluggishness

- Add cached localhost field to TuiApp struct to avoid repeated gethostname() system calls
- Initialize localhost once in constructor instead of calling gethostname() on every navigation
- Replace gethostname() calls in update_hosts() and navigate_host() with cached value
- Eliminate expensive system call bottleneck causing Tab key responsiveness issues
- Reduce Tab navigation from 2+ system calls to zero system calls (memory access only)
- Fix performance regression introduced by immediate UI refresh implementation
- Bump version to 0.1.60

Cargo.lock

@@ -270,7 +270,7 @@ checksum = "a1d728cc89cf3aee9ff92b05e62b19ee65a02b5702cff7d5a377e32c6ae29d8d"
 
 [[package]]
 name = "cm-dashboard"
-version = "0.1.56"
+version = "0.1.59"
 dependencies = [
  "anyhow",
  "chrono",
@@ -292,7 +292,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-agent"
-version = "0.1.56"
+version = "0.1.59"
 dependencies = [
  "anyhow",
  "async-trait",
@@ -315,7 +315,7 @@ dependencies = [
 
 [[package]]
 name = "cm-dashboard-shared"
-version = "0.1.56"
+version = "0.1.59"
 dependencies = [
  "chrono",
  "serde",

agent/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-dashboard-agent"
-version = "0.1.57"
+version = "0.1.60"
 edition = "2021"
 
 [dependencies]

dashboard/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-dashboard"
-version = "0.1.57"
+version = "0.1.60"
 edition = "2021"
 
 [dependencies]

dashboard/src/app.rs

@@ -191,6 +191,17 @@ impl Dashboard {
                         break;
                     }
                 }
+
+                // Render UI immediately after handling input for responsive feedback
+                if let Some(ref mut terminal) = self.terminal {
+                    if let Some(ref mut tui_app) = self.tui_app {
+                        if let Err(e) = terminal.draw(|frame| {
+                            tui_app.render(frame, &self.metric_store);
+                        }) {
+                            error!("Error rendering TUI after input: {}", e);
+                        }
+                    }
+                }
             }
 
             // Check for new metrics

dashboard/src/ui/mod.rs

@@ -90,10 +90,13 @@ pub struct TuiApp {
     user_navigated_away: bool,
     /// Dashboard configuration
     config: DashboardConfig,
+    /// Cached localhost hostname to avoid repeated system calls
+    localhost: String,
 }
 
 impl TuiApp {
     pub fn new(config: DashboardConfig) -> Self {
+        let localhost = gethostname::gethostname().to_string_lossy().to_string();
         let mut app = Self {
             host_widgets: HashMap::new(),
             current_host: None,
@@ -102,6 +105,7 @@ impl TuiApp {
             should_quit: false,
             user_navigated_away: false,
             config,
+            localhost,
         };
         
         // Sort predefined hosts
@@ -131,31 +135,31 @@ impl TuiApp {
             // Only update widgets if we have metrics for this host
             let all_metrics = metric_store.get_metrics_for_host(&hostname);
             if !all_metrics.is_empty() {
-                // Get metrics first while hostname is borrowed
-                let cpu_metrics: Vec<&Metric> = all_metrics
-                    .iter()
-                    .filter(|m| {
-                        m.name.starts_with("cpu_")
-                            || m.name.contains("c_state_")
-                            || m.name.starts_with("process_top_")
-                    })
-                    .copied()
-                    .collect();
-                let memory_metrics: Vec<&Metric> = all_metrics
-                    .iter()
-                    .filter(|m| m.name.starts_with("memory_") || m.name.starts_with("disk_tmp_"))
-                    .copied()
-                    .collect();
-                let service_metrics: Vec<&Metric> = all_metrics
-                    .iter()
-                    .filter(|m| m.name.starts_with("service_"))
-                    .copied()
-                    .collect();
-                let all_backup_metrics: Vec<&Metric> = all_metrics
-                    .iter()
-                    .filter(|m| m.name.starts_with("backup_"))
-                    .copied()
-                    .collect();
+                // Single pass metric categorization for better performance
+                let mut cpu_metrics = Vec::new();
+                let mut memory_metrics = Vec::new();
+                let mut service_metrics = Vec::new();
+                let mut backup_metrics = Vec::new();
+                let mut nixos_metrics = Vec::new();
+                let mut disk_metrics = Vec::new();
+                
+                for metric in all_metrics {
+                    if metric.name.starts_with("cpu_") 
+                        || metric.name.contains("c_state_") 
+                        || metric.name.starts_with("process_top_") {
+                        cpu_metrics.push(metric);
+                    } else if metric.name.starts_with("memory_") || metric.name.starts_with("disk_tmp_") {
+                        memory_metrics.push(metric);
+                    } else if metric.name.starts_with("service_") {
+                        service_metrics.push(metric);
+                    } else if metric.name.starts_with("backup_") {
+                        backup_metrics.push(metric);
+                    } else if metric.name == "system_nixos_build" || metric.name == "system_active_users" || metric.name == "agent_version" {
+                        nixos_metrics.push(metric);
+                    } else if metric.name.starts_with("disk_") {
+                        disk_metrics.push(metric);
+                    }
+                }
 
                 // Clear completed transitions first
                 self.clear_completed_transitions(&hostname, &service_metrics);
@@ -166,21 +170,7 @@ impl TuiApp {
                 // Collect all system metrics (CPU, memory, NixOS, disk/storage)
                 let mut system_metrics = cpu_metrics;
                 system_metrics.extend(memory_metrics);
-                
-                // Add NixOS metrics - using exact matching for build display fix
-                let nixos_metrics: Vec<&Metric> = all_metrics
-                    .iter()
-                    .filter(|m| m.name == "system_nixos_build" || m.name == "system_active_users" || m.name == "agent_version")
-                    .copied()
-                    .collect();
                 system_metrics.extend(nixos_metrics);
-                
-                // Add disk/storage metrics
-                let disk_metrics: Vec<&Metric> = all_metrics
-                    .iter()
-                    .filter(|m| m.name.starts_with("disk_"))
-                    .copied()
-                    .collect();
                 system_metrics.extend(disk_metrics);
 
                 host_widgets.system_widget.update_from_metrics(&system_metrics);
@@ -189,7 +179,7 @@ impl TuiApp {
                     .update_from_metrics(&service_metrics);
                 host_widgets
                     .backup_widget
-                    .update_from_metrics(&all_backup_metrics);
+                    .update_from_metrics(&backup_metrics);
 
                 host_widgets.last_update = Some(Instant::now());
             }
@@ -221,13 +211,12 @@ impl TuiApp {
         self.available_hosts = all_hosts;
         
         // Get the current hostname (localhost) for auto-selection
-        let localhost = gethostname::gethostname().to_string_lossy().to_string();
         if !self.available_hosts.is_empty() {
-            if self.available_hosts.contains(&localhost) && !self.user_navigated_away {
+            if self.available_hosts.contains(&self.localhost) && !self.user_navigated_away {
                 // Localhost is available and user hasn't navigated away - switch to it
-                self.current_host = Some(localhost.clone());
+                self.current_host = Some(self.localhost.clone());
                 // Find the actual index of localhost in the sorted list
-                self.host_index = self.available_hosts.iter().position(|h| h == &localhost).unwrap_or(0);
+                self.host_index = self.available_hosts.iter().position(|h| h == &self.localhost).unwrap_or(0);
             } else if self.current_host.is_none() {
                 // No current host - select first available (which is localhost if available)
                 self.current_host = Some(self.available_hosts[0].clone());
@@ -424,9 +413,8 @@ impl TuiApp {
         self.current_host = Some(self.available_hosts[self.host_index].clone());
         
         // Check if user navigated away from localhost
-        let localhost = gethostname::gethostname().to_string_lossy().to_string();
         if let Some(ref current) = self.current_host {
-            if current != &localhost {
+            if current != &self.localhost {
                 self.user_navigated_away = true;
             } else {
                 self.user_navigated_away = false; // User navigated back to localhost

shared/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-dashboard-shared"
-version = "0.1.57"
+version = "0.1.60"
 edition = "2021"
 
 [dependencies]