perf: fix critical vm.runInContext overhead (30x speedup)

CRITICAL FIX:
- vm.Script.runInContext() has 30x overhead on EVERY function call
- Even with cached context, each invocation crosses VM boundary
- Changed to use new Function() for fast path (no context)
- Inject 'require' parameter to maintain Node.js compatibility

BEFORE: turbo(1M items) = 7779ms (36x slower than raw JS)
AFTER:  turbo(1M items) = 308ms (1.5x overhead, acceptable)
        turbo(8 workers) = 190ms (1.1x FASTER than raw JS!)

This fix affects both:
- dist/worker.js (file workers)
- INLINE_WORKER_CODE (bundled workers)

Author: samsantosb

src/cache.ts

@@ -135,26 +135,6 @@ const BASE_GLOBALS: Record<string, unknown> = {
   TextDecoder
 };
 
-/**
- * Shared base context - created ONCE per worker, reused for all executions.
- * @internal
- */
-let BASE_CONTEXT: vm.Context | null = null;
-
-/**
- * Gets or creates the shared base context.
- * Lazy initialization - only created when first needed.
- *
- * @returns The shared base context
- * @internal
- */
-function getBaseContext(): vm.Context {
-  if (!BASE_CONTEXT) {
-    BASE_CONTEXT = vm.createContext(Object.assign({}, BASE_GLOBALS));
-  }
-  return BASE_CONTEXT;
-}
-
 /**
  * Creates a sandbox efficiently by inheriting from BASE_GLOBALS.
  *
@@ -497,24 +477,29 @@ export function createFunctionCache(maxSize: number = DEFAULT_MAX_SIZE, ttl = DE
         return fn;
       }
 
-      // Cache miss - compile with vm.Script (no eval!)
+      // Cache miss - compile function
       misses++;
 
-      const code = `(${fnString})`;
-      const script = new vm.Script(code, {
-        filename: 'bee-worker-fn.js',
-        produceCachedData: true // Enable V8 code caching
-      });
-
       // ─────────────────────────────────────────────────────────────────────
-      // CRITICAL: Reuse shared context when no custom context needed (90%)
-      // This avoids creating a new V8 context (~1-2MB each!) per execution
+      // CRITICAL PERFORMANCE FIX:
+      // vm.Script.runInContext() has 30x overhead on EVERY function call!
+      // Even with cached context, each invocation crosses VM boundary.
+      // 
+      // Solution: Use new Function() when no context needed (fast path)
+      //           Only use runInContext() when context injection is required
       // ─────────────────────────────────────────────────────────────────────
       if (!hasContext) {
-        // No context = run in shared base context (zero memory overhead)
-        fn = script.runInContext(getBaseContext()) as Function;
+        // FAST PATH: No context = use new Function() (30x faster!)
+        // new Function() creates native functions without VM boundary overhead
+        // We inject 'require' to maintain Node.js compatibility
+        fn = (new Function('require', 'return ' + fnString))(require) as Function;
       } else {
-        // Has context = need sandbox for closure variable injection
+        // SLOW PATH: Has context = must use vm.Script for context injection
+        const code = `(${fnString})`;
+        const script = new vm.Script(code, {
+          filename: 'bee-worker-fn.js',
+          produceCachedData: true // Enable V8 code caching
+        });
         const sandbox = createSandbox(context);
         vm.createContext(sandbox);
         fn = script.runInContext(sandbox) as Function;

src/inline-workers.ts

@@ -126,22 +126,22 @@ function compile(src, context) {
   const processedContext = reconstructContext(context);
   
   // IMPORTANT: Cache key must include context VALUES, not just keys!
-  // Otherwise two calls with same function but different context values
-  // would incorrectly return the cached function compiled with old values.
-  const ctxKey = processedContext ? JSON.stringify(context) : ''; // Use original for cache key
+  const ctxKey = processedContext ? JSON.stringify(context) : '';
   const key = src + '::' + ctxKey;
   let fn = LOW_MEMORY ? null : cacheGet(key);
   if (fn) return fn;
 
-  const script = new vm.Script('(' + src + ')', { filename: 'bee-worker.js' });
-  
   if (processedContext && Object.keys(processedContext).length > 0) {
+    // With context: use vm.Script (slower but needed for context injection)
+    const script = new vm.Script('(' + src + ')', { filename: 'bee-worker.js' });
     const sandbox = Object.create(getBaseContext());
     const keys = Object.keys(processedContext);
     for (let i = 0; i < keys.length; i++) sandbox[keys[i]] = processedContext[keys[i]];
     fn = script.runInContext(vm.createContext(sandbox));
   } else {
-    fn = script.runInContext(getBaseContext());
+    // FAST PATH: No context - use new Function() which is 30x faster!
+    // vm.runInContext() has massive overhead even with cached context
+    fn = (new Function('return ' + src))();
   }
   
   if (!LOW_MEMORY) cacheSet(key, fn);
@@ -425,21 +425,20 @@ function compile(src, context) {
   const processedContext = reconstructContext(context);
   
   // IMPORTANT: Cache key must include context VALUES, not just keys!
-  // Otherwise two calls with same function but different context values
-  // would incorrectly return the cached function compiled with old values.
   const ctxKey = processedContext ? JSON.stringify(context) : '';
   const key = src + '::' + ctxKey;
   let fn = LOW_MEMORY ? null : cacheGet(key);
   if (fn) return fn;
 
-  const script = new vm.Script('(' + src + ')', { filename: 'bee-generator.js' });
-  
   if (processedContext && Object.keys(processedContext).length > 0) {
+    // With context: use vm.Script (slower but needed for context injection)
+    const script = new vm.Script('(' + src + ')', { filename: 'bee-generator.js' });
     const sandbox = Object.create(getBaseContext());
     for (const k of Object.keys(processedContext)) sandbox[k] = processedContext[k];
     fn = script.runInContext(vm.createContext(sandbox));
   } else {
-    fn = script.runInContext(getBaseContext());
+    // FAST PATH: No context - use new Function() which is 30x faster!
+    fn = (new Function('return ' + src))();
   }
   
   if (!LOW_MEMORY) cacheSet(key, fn);