feat(benchmark infra) Add beforeEachBatchAsync callback

tools/benchmark/src/Configuration.ts

@@ -209,8 +209,7 @@ export interface BenchmarkTimingOptions {
 }
 
 /**
- * Set of options that can be provided to a benchmark. These options generally align with the BenchmarkJS options type;
- * you can see more documentation {@link https://benchmarkjs.com/docs#options | here}.
+ * Operations that can be performed on a per-batch basis
  * @public
  */
 export interface OnBatch {
@@ -223,6 +222,16 @@ export interface OnBatch {
 	 * iterations per batch.
 	 */
 	beforeEachBatch?: () => void;
+
+	/**
+	 * Executes Async code before the start of each batch. This has the same semantics as benchmarkjs's `onCycle`:
+	 * https://benchmarkjs.com/docs/#options_onCycle
+	 *
+	 * @remarks
+	 * Beware that batches run `benchmarkFn` more than once: a typical micro-benchmark might involve 10k
+	 * iterations per batch.
+	 */
+	beforeEachBatchAsync?: () => Promise<void>;
 }
 
 /**

tools/benchmark/src/runBenchmark.ts

@@ -244,7 +244,7 @@ export async function runBenchmarkAsync(
 			await doBatchAsync(
 				state.iterationsPerBatch,
 				args.benchmarkFnAsync,
-				args.beforeEachBatch,
+				args.beforeEachBatchAsync,
 			),
 		)
 	) {
@@ -277,9 +277,9 @@ function doBatch(
 async function doBatchAsync(
 	iterationCount: number,
 	f: () => Promise<unknown>,
-	beforeEachBatch: undefined | (() => void),
+	beforeEachBatchAsync: undefined | (() => Promise<void>),
 ): Promise<number> {
-	beforeEachBatch?.();
+	await beforeEachBatchAsync?.();
 	let i = iterationCount;
 	const before = timer.now();
 	while (i--) {