⚡ Bolt: [performance improvement] Batched GC file operations

.jules/bolt.md

@@ -0,0 +1,6 @@
+## 2024-05-15 - Batched concurrent I/O operations for large file iterations
+**Learning:** Sequential await calls in loops for operations like `fs.stat` or `fs.rm` over large directories (e.g. ArtifactStore.gc) cause severe performance bottlenecks and can trigger EMFILE limits.
+**Action:** Always batch I/O operations using `Promise.all` with a reasonable chunk size (e.g. 10) to parallelize without hitting EMFILE limits.
+## 2024-05-15 - Array.find inside batched iterations causes O(N^2) regressions
+**Learning:** In batched loops, such as when calling `isExpired` inside `evictExpiredEntries`, calling `this.cacheStore.get()` inside the loop performs an O(N) lookup. Since the loop runs O(N) times, the overall complexity becomes O(N^2), causing performance regressions.
+**Action:** Always reuse the entry objects obtained during the initial O(N) iteration rather than fetching them again.

src/core/sub-agent/artifacts/store.ts

@@ -93,13 +93,27 @@ export class ArtifactStore {
     const entries = await fs.readdir(root, { withFileTypes: true }).catch(() => []);
 
     const files: Array<{ name: string; path: string; mtimeMs: number; size: number }> = [];
-    for (const entry of entries) {
-      if (!entry.isFile()) continue;
+    const validEntries = entries.filter((entry) => {
+      if (!entry.isFile()) return false;
       const filePath = path.join(root, entry.name);
-      if (!isWithinDir(root, filePath)) continue;
-      const stat = await fs.stat(filePath).catch(() => null);
-      if (!stat) continue;
-      files.push({ name: entry.name, path: filePath, mtimeMs: stat.mtimeMs, size: stat.size });
+      return isWithinDir(root, filePath);
+    });
+
+    for (let i = 0; i < validEntries.length; i += 10) {
+      const chunk = validEntries.slice(i, i + 10);
+      const stats = await Promise.all(
+        chunk.map(async (entry) => {
+          const filePath = path.join(root, entry.name);
+          const stat = await fs.stat(filePath).catch(() => null);
+          return { entry, filePath, stat };
+        }),
+      );
+
+      for (const { entry, filePath, stat } of stats) {
+        if (stat) {
+          files.push({ name: entry.name, path: filePath, mtimeMs: stat.mtimeMs, size: stat.size });
+        }
+      }
     }
 
     const maxAgeMs = options?.maxAgeMs ?? LIMITS.artifactTtlMs;
@@ -118,8 +132,9 @@ export class ArtifactStore {
       removedBytes += file.size;
     };
 
-    for (const file of expired) {
-      await removeFile(file);
+    for (let i = 0; i < expired.length; i += 10) {
+      const chunk = expired.slice(i, i + 10);
+      await Promise.all(chunk.map((file) => removeFile(file)));
     }
 
     // Recompute remaining after TTL removal (newest first).
@@ -130,17 +145,23 @@ export class ArtifactStore {
     let currentFiles = remaining.length;
     let currentBytes = remaining.reduce((acc, f) => acc + f.size, 0);
 
+    const excessFilesToRemove = [];
     for (let i = remaining.length - 1; i >= 0; i--) {
       const tooManyFiles = currentFiles > maxFiles;
       const tooManyBytes = currentBytes > maxTotalBytes;
       if (!tooManyFiles && !tooManyBytes) break;
 
       const oldest = remaining[i];
-      await removeFile(oldest);
+      excessFilesToRemove.push(oldest);
       currentFiles -= 1;
       currentBytes -= oldest.size;
     }
 
+    for (let i = 0; i < excessFilesToRemove.length; i += 10) {
+      const chunk = excessFilesToRemove.slice(i, i + 10);
+      await Promise.all(chunk.map((file) => removeFile(file)));
+    }
+
     return { removedFiles, removedBytes };
   }