[model-gateway] Optimize HashRing construction to reduce heap allocations (#17575)

sgl-model-gateway/src/core/worker_registry.rs

@@ -57,11 +57,16 @@ impl HashRing {
         for worker in workers {
             // Create Arc<str> once per worker, share across all virtual nodes
             let url: Arc<str> = Arc::from(worker.url());
+            let url_bytes = url.as_bytes();
 
             // Create multiple virtual nodes per worker
             for vnode in 0..VIRTUAL_NODES_PER_WORKER {
-                let vnode_key = format!("{}#{}", url, vnode);
-                let pos = Self::hash_position(&vnode_key);
+                let mut hasher = blake3::Hasher::new();
+                hasher.update(url_bytes);
+                hasher.update(b"#");
+                hasher.update(&(vnode as u64).to_le_bytes());
+                let hash = hasher.finalize();
+                let pos = u64::from_le_bytes(hash.as_bytes()[..8].try_into().unwrap());
                 entries.push((pos, Arc::clone(&url)));
             }
         }