[model-gateway] Optimize consistent hashing hot path to eliminate allocations (#17467)

sgl-model-gateway/benches/consistent_hash_bench.rs

@@ -0,0 +1,36 @@
+use criterion::{black_box, criterion_group, criterion_main, BenchmarkId, Criterion};
+use smg::mesh::consistent_hash::ConsistentHashRing;
+
+fn setup_ring(node_count: usize) -> ConsistentHashRing {
+    let mut ring = ConsistentHashRing::new();
+    for i in 0..node_count {
+        ring.add_node(&format!("node-{}", i));
+    }
+    ring
+}
+
+fn bench_consistent_hash(c: &mut Criterion) {
+    let mut group = c.benchmark_group("ConsistentHashRing");
+
+    for size in [10, 100, 500].iter() {
+        let ring = setup_ring(*size);
+        let key = "test-request-key-for-rate-limiting";
+        let node_name = "node-5";
+
+        group.bench_with_input(BenchmarkId::new("get_owners", size), size, |b, _| {
+            b.iter(|| {
+                black_box(ring.get_owners(key));
+            });
+        });
+        group.bench_with_input(BenchmarkId::new("is_owner", size), size, |b, _| {
+            b.iter(|| {
+                black_box(ring.is_owner(key, node_name));
+            });
+        });
+    }
+
+    group.finish();
+}
+
+criterion_group!(benches, bench_consistent_hash);
+criterion_main!(benches);