sgl-router: experimental Rust HTTP router for SGLang worker pools (#25851)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

experimental/sgl-router/benches/tree_lookup.rs

@@ -0,0 +1,89 @@
+// SPDX-FileCopyrightText: Copyright (c) 2026 The SGLang Authors
+// SPDX-License-Identifier: Apache-2.0
+
+//! Cache-aware tree-lookup microbench.
+//!
+//! Mirrors the shape of `sgl-model-gateway/benches/radix_tree_benchmark.rs`
+//! (specifically the `TokenTree` / `PositionalIndexer` paths — which serve
+//! the same role as sgl-router's `HashTree`). The bench measures:
+//!
+//!   * `insert` — populate one worker's prefix.
+//!   * `match_prefix` — score an incoming request against the tree.
+//!
+//! Output is `criterion`'s default (target/criterion/...). To run:
+//!
+//!   cargo bench --bench tree_lookup
+//!   cargo bench --bench tree_lookup -- --sample-size 30   # faster
+//!
+//! See `BENCHMARKS.md` for the SMG↔sgl-router comparison table.
+
+use criterion::{black_box, criterion_group, criterion_main, BenchmarkId, Criterion, Throughput};
+use rand::rngs::StdRng;
+use rand::{Rng, SeedableRng};
+use sgl_router::policies::kv_events::tree::{HashTree, KvWorkerId};
+
+fn build_tree(num_workers: usize, blocks_per_worker: usize, seed: u64) -> HashTree {
+    let tree = HashTree::new();
+    let mut rng = StdRng::seed_from_u64(seed);
+    for w in 0..num_workers {
+        let worker = KvWorkerId::new(format!("http://w{w}:30000"), 0);
+        // Each worker holds a distinct (random) prefix so the trees fan
+        // out — this is the realistic case for cache-aware routing.
+        let hashes: Vec<i64> = (0..blocks_per_worker).map(|_| rng.gen::<i64>()).collect();
+        tree.insert(&worker, None, &hashes);
+    }
+    tree
+}
+
+fn bench_insert(c: &mut Criterion) {
+    let mut group = c.benchmark_group("hashtree_insert");
+    for &n_blocks in &[8usize, 32, 128, 512] {
+        group.throughput(Throughput::Elements(n_blocks as u64));
+        group.bench_with_input(BenchmarkId::from_parameter(n_blocks), &n_blocks, |b, &n| {
+            let mut rng = StdRng::seed_from_u64(0xC0FFEE);
+            let hashes: Vec<i64> = (0..n).map(|_| rng.gen::<i64>()).collect();
+            b.iter_batched(
+                HashTree::new,
+                |tree| {
+                    let worker = KvWorkerId::new("http://w:30000".to_string(), 0);
+                    tree.insert(&worker, None, black_box(&hashes));
+                    tree
+                },
+                criterion::BatchSize::SmallInput,
+            );
+        });
+    }
+    group.finish();
+}
+
+fn bench_match_prefix(c: &mut Criterion) {
+    let mut group = c.benchmark_group("hashtree_match_prefix");
+    // (workers, blocks_per_worker, query_len) cases that span the
+    // realistic operating window: small fleet w/ moderate prefixes,
+    // medium fleet w/ long prefixes, and a stress case.
+    let cases = [
+        (4usize, 32usize, 8usize),
+        (16, 64, 32),
+        (64, 128, 64),
+        (128, 256, 128),
+    ];
+    for (workers, bpw, query_len) in cases {
+        let label = format!("w{workers}_bpw{bpw}_q{query_len}");
+        group.throughput(Throughput::Elements(query_len as u64));
+        let tree = build_tree(workers, bpw, 0xDEADBEEF);
+        // Pull one real worker's prefix so the query has a non-trivial
+        // partial match — closer to the production hot path.
+        let mut rng = StdRng::seed_from_u64(0x12345);
+        let probe: Vec<i64> = (0..query_len).map(|_| rng.gen::<i64>()).collect();
+        group.bench_function(label, |b| {
+            b.iter(|| {
+                let m = tree.match_prefix(None, black_box(&probe));
+                black_box(m.matched_blocks)
+            });
+        });
+    }
+    group.finish();
+}
+
+criterion_group!(benches, bench_insert, bench_match_prefix);
+criterion_main!(benches);