add execution trace

Author: Shourya742

src/bootstrap/src/utils/exec.rs

@@ -75,8 +75,7 @@ pub struct CommandCacheKey {
 
 #[derive(Default, Clone)]
 pub struct CommandProfile {
-    pub count: usize,
-    pub durations: Vec<Duration>,
+    pub exec_traces: Vec<ExecutionTrace>,
 }
 
 #[derive(Default)]
@@ -85,14 +84,19 @@ pub struct CommandProfiler {
 }
 
 impl CommandProfiler {
-    pub fn record(&self, key: CommandCacheKey, duration: Duration) {
+    pub fn record(&self, key: CommandCacheKey, exec_trace: ExecutionTrace) {
         let mut stats = self.stats.lock().unwrap();
         let entry = stats.entry(key).or_default();
-        entry.count += 1;
-        entry.durations.push(duration);
+        entry.exec_traces.push(exec_trace);
     }
 }
 
+#[derive(Clone)]
+pub enum ExecutionTrace {
+    CacheHit { timestamp: Instant },
+    Executed { timestamp: Instant, duration: Duration },
+}
+
 /// Wrapper around `std::process::Command`.
 ///
 /// By default, the command will exit bootstrap if it fails.
@@ -568,7 +572,7 @@ impl ExecutionContext {
         if let Some(cached_output) = self.command_cache.get(&cache_key) {
             command.mark_as_executed();
             self.verbose(|| println!("Cache hit: {command:?}"));
-            self.profiler.record(cache_key, Duration::from_secs(0));
+            self.profiler.record(cache_key, ExecutionTrace::CacheHit { timestamp: Instant::now() });
             return DeferredCommand { state: CommandState::Cached(cached_output) };
         }
 
@@ -716,8 +720,13 @@ impl<'a> DeferredCommand<'a> {
                     && command.should_cache
                 {
                     exec_ctx.command_cache.insert(cache_key.clone(), output.clone());
-                    let duration = start_time.elapsed();
-                    exec_ctx.profiler.record(cache_key.clone(), duration);
+                    exec_ctx.profiler.record(
+                        cache_key.clone(),
+                        ExecutionTrace::Executed {
+                            timestamp: start_time,
+                            duration: start_time.elapsed(),
+                        },
+                    );
                 }
 
                 output