From be6f63a740c857c1f6c9b5b569eedfa9e4fdc7c5 Mon Sep 17 00:00:00 2001
From: Anatol Belski <anbelski@linux.microsoft.com>
Date: Sat, 14 Mar 2026 15:28:14 +0100
Subject: [PATCH] performance-metrics: Add util module with shared micro
 benchmark helpers

These factor out common setup and synchronization patterns used by block
layer micro benchmarks.

Signed-off-by: Anatol Belski <anbelski@linux.microsoft.com>
---
 Cargo.lock                      |  1 +
 performance-metrics/Cargo.toml  |  1 +
 performance-metrics/src/main.rs |  1 +
 performance-metrics/src/util.rs | 36 +++++++++++++++++++++++++++++++++
 4 files changed, 39 insertions(+)
 create mode 100644 performance-metrics/src/util.rs

diff --git a/Cargo.lock b/Cargo.lock
index 083f42101..af88d4db9 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1602,6 +1602,7 @@ dependencies = [
  "serde_json",
  "test_infra",
  "thiserror 2.0.18",
+ "vmm-sys-util",
 ]
 
 [[package]]
diff --git a/performance-metrics/Cargo.toml b/performance-metrics/Cargo.toml
index 472f1159b..60be8f45a 100644
--- a/performance-metrics/Cargo.toml
+++ b/performance-metrics/Cargo.toml
@@ -11,6 +11,7 @@ serde = { workspace = true, features = ["derive", "rc"] }
 serde_json = { workspace = true }
 test_infra = { path = "../test_infra" }
 thiserror = { workspace = true }
+vmm-sys-util = { workspace = true }
 
 [lints]
 workspace = true
diff --git a/performance-metrics/src/main.rs b/performance-metrics/src/main.rs
index cdc06fe10..bcfee6d97 100644
--- a/performance-metrics/src/main.rs
+++ b/performance-metrics/src/main.rs
@@ -5,6 +5,7 @@
 
 // Custom harness to run performance tests
 mod performance_tests;
+mod util;
 
 use std::process::Command;
 use std::sync::Arc;
diff --git a/performance-metrics/src/util.rs b/performance-metrics/src/util.rs
new file mode 100644
index 000000000..dcc225750
--- /dev/null
+++ b/performance-metrics/src/util.rs
@@ -0,0 +1,36 @@
+// Copyright 2026 The Cloud Hypervisor Authors. All rights reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+
+//! Shared benchmark helpers.
+
+use std::io::ErrorKind;
+use std::thread;
+use std::time::Duration;
+
+use vmm_sys_util::eventfd::EventFd;
+use vmm_sys_util::tempfile::TempFile;
+
+pub const BLOCK_SIZE: u64 = 4096;
+
+/// Create a temporary file pre sized to hold `num_blocks` blocks.
+pub fn sized_tempfile(num_blocks: usize) -> TempFile {
+    let tmp = TempFile::new().expect("failed to create tempfile");
+    tmp.as_file()
+        .set_len(BLOCK_SIZE * num_blocks as u64)
+        .expect("failed to set file length");
+    tmp
+}
+
+/// Spin and wait until the given eventfd becomes readable.
+pub fn wait_for_eventfd(notifier: &EventFd) {
+    loop {
+        match notifier.read() {
+            Ok(_) => return,
+            Err(e) if e.kind() == ErrorKind::WouldBlock => {
+                thread::sleep(Duration::from_micros(50));
+            }
+            Err(e) => panic!("eventfd read failed: {e}"),
+        }
+    }
+}