--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/third_party/libuv/test/benchmark-async.c	Wed Jan 14 19:39:52 2026 -0800
@@ -0,0 +1,142 @@
+/* Copyright Joyent, Inc. and other Node contributors. All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "task.h"
+#include "uv.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#define NUM_PINGS (1000 * 1000)
+
+struct ctx {
+  uv_loop_t loop;
+  uv_thread_t thread;
+  uv_async_t main_async;    /* wake up main thread */
+  uv_async_t worker_async;  /* wake up worker */
+  unsigned int nthreads;
+  unsigned int main_sent;
+  unsigned int main_seen;
+  unsigned int worker_sent;
+  unsigned int worker_seen;
+};
+
+
+static void worker_async_cb(uv_async_t* handle) {
+  struct ctx* ctx = container_of(handle, struct ctx, worker_async);
+
+  ASSERT_OK(uv_async_send(&ctx->main_async));
+  ctx->worker_sent++;
+  ctx->worker_seen++;
+
+  if (ctx->worker_sent >= NUM_PINGS)
+    uv_close((uv_handle_t*) &ctx->worker_async, NULL);
+}
+
+
+static void main_async_cb(uv_async_t* handle) {
+  struct ctx* ctx = container_of(handle, struct ctx, main_async);
+
+  ASSERT_OK(uv_async_send(&ctx->worker_async));
+  ctx->main_sent++;
+  ctx->main_seen++;
+
+  if (ctx->main_sent >= NUM_PINGS)
+    uv_close((uv_handle_t*) &ctx->main_async, NULL);
+}
+
+
+static void worker(void* arg) {
+  struct ctx* ctx = arg;
+  ASSERT_OK(uv_async_send(&ctx->main_async));
+  ASSERT_OK(uv_run(&ctx->loop, UV_RUN_DEFAULT));
+  uv_loop_close(&ctx->loop);
+}
+
+
+static int test_async(int nthreads) {
+  char fmtbuf[32];
+  struct ctx* threads;
+  struct ctx* ctx;
+  uint64_t time;
+  int i;
+
+  threads = calloc(nthreads, sizeof(threads[0]));
+  ASSERT_NOT_NULL(threads);
+
+  for (i = 0; i < nthreads; i++) {
+    ctx = threads + i;
+    ctx->nthreads = nthreads;
+    ASSERT_OK(uv_loop_init(&ctx->loop));
+    ASSERT_OK(uv_async_init(&ctx->loop, &ctx->worker_async, worker_async_cb));
+    ASSERT_OK(uv_async_init(uv_default_loop(),
+                            &ctx->main_async,
+                            main_async_cb));
+    ASSERT_OK(uv_thread_create(&ctx->thread, worker, ctx));
+  }
+
+  time = uv_hrtime();
+
+  ASSERT_OK(uv_run(uv_default_loop(), UV_RUN_DEFAULT));
+
+  for (i = 0; i < nthreads; i++)
+    ASSERT_OK(uv_thread_join(&threads[i].thread));
+
+  time = uv_hrtime() - time;
+
+  for (i = 0; i < nthreads; i++) {
+    ctx = threads + i;
+    ASSERT_EQ(ctx->worker_sent, NUM_PINGS);
+    ASSERT_EQ(ctx->worker_seen, NUM_PINGS);
+    ASSERT_EQ(ctx->main_sent, (unsigned int) NUM_PINGS);
+    ASSERT_EQ(ctx->main_seen, (unsigned int) NUM_PINGS);
+  }
+
+  printf("async%d: %.2f sec (%s/sec)\n",
+         nthreads,
+         time / 1e9,
+         fmt(&fmtbuf, NUM_PINGS / (time / 1e9)));
+
+  free(threads);
+
+  MAKE_VALGRIND_HAPPY(uv_default_loop());
+  return 0;
+}
+
+
+BENCHMARK_IMPL(async1) {
+  return test_async(1);
+}
+
+
+BENCHMARK_IMPL(async2) {
+  return test_async(2);
+}
+
+
+BENCHMARK_IMPL(async4) {
+  return test_async(4);
+}
+
+
+BENCHMARK_IMPL(async8) {
+  return test_async(8);
+}