added note about RwLock

src/main.rs

@@ -161,6 +161,7 @@ struct BlobManager {
     // Also note RwLock (create) starvation might be a concern if caller is
     // append/read heavy due to platform-defined fairness
     // todo: better approach?
+    // RwLock benefits shrink as create traffic becomes heavy
 }
 
 // todo: blob indexing is left up to the caller maybe add ID generator