test(tvix/eval): Add attr merge benchmarks r/4615

Add a quick couple of benchmarks for merging attribute sets, large and
small.

Change-Id: I26940a9cf4e0d30e3d9eb07a7b8c366ca4072ca3
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6286
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: grfn <grfn@gws.fyi>

3 files changed, 19 insertions, 1 deletions

diff --git a/tvix/eval/Cargo.lock b/tvix/eval/Cargo.lock
index 05bcd8ccd2..4732d1b002 100644
--- a/tvix/eval/Cargo.lock
+++ b/tvix/eval/Cargo.lock
@@ -874,6 +874,7 @@ version = "0.1.0"
 dependencies = [
  "criterion",
  "dirs",
+ "itertools",
  "path-clean",
  "pretty_assertions",
  "rnix",
diff --git a/tvix/eval/Cargo.toml b/tvix/eval/Cargo.toml
index 21c2243473..32fa9e2573 100644
--- a/tvix/eval/Cargo.toml
+++ b/tvix/eval/Cargo.toml
@@ -23,6 +23,7 @@ rev = "614e7d4641e83ab7eb321d9ac5e3d12985f9f3ba"
 criterion = "0.3.6"
 test-generator = "0.3.0"
 pretty_assertions = "1.2.1"
+itertools = "0.10.3"
 
 [features]
 # Enables running the Nix language test suite from the original C++
diff --git a/tvix/eval/benches/eval.rs b/tvix/eval/benches/eval.rs
index a05c04f03e..9be381e0f8 100644
--- a/tvix/eval/benches/eval.rs
+++ b/tvix/eval/benches/eval.rs
@@ -1,9 +1,25 @@
 use criterion::{black_box, criterion_group, criterion_main, Criterion};
+use itertools::Itertools;
 use tvix_eval::interpret;
 
 fn eval_literals(c: &mut Criterion) {
     c.bench_function("int", |b| b.iter(|| black_box(interpret("42", None))));
 }
 
-criterion_group!(benches, eval_literals);
+fn eval_merge_attrs(c: &mut Criterion) {
+    c.bench_function("merge small attrs", |b| {
+        b.iter(|| black_box(interpret("{ a = 1; b = 2; } // { c = 3; }", None)))
+    });
+
+    c.bench_function("merge large attrs with small attrs", |b| {
+        let large_attrs = format!(
+            "{{{}}}",
+            (0..10000).map(|n| format!("a{n} = {n};")).join(" ")
+        );
+        let expr = format!("{large_attrs} // {{ c = 3; }}");
+        b.iter(move || black_box(interpret(&expr, None)))
+    });
+}
+
+criterion_group!(benches, eval_literals, eval_merge_attrs);
 criterion_main!(benches);