diff --git a/performance-metrics/src/main.rs b/performance-metrics/src/main.rs
index 93ab45e31..14ecfb12b 100644
--- a/performance-metrics/src/main.rs
+++ b/performance-metrics/src/main.rs
@@ -378,7 +378,7 @@ mod adjuster {
     }
 }
 
-const TEST_LIST: [PerformanceTest; 68] = [
+const TEST_LIST: [PerformanceTest; 70] = [
     PerformanceTest {
         name: "boot_time_ms",
         func_ptr: performance_boot_time,
@@ -1325,6 +1325,30 @@ const TEST_LIST: [PerformanceTest; 68] = [
         },
         unit_adjuster: adjuster::s_to_us,
     },
+    PerformanceTest {
+        name: "micro_block_qcow_fsync_128_us",
+        func_ptr: micro_bench_block::micro_bench_qcow_fsync,
+        control: PerformanceTestControl {
+            test_timeout: 10,
+            test_iterations: 20,
+            warmup_iterations: 5,
+            num_ops: Some(128),
+            ..PerformanceTestControl::default()
+        },
+        unit_adjuster: adjuster::s_to_us,
+    },
+    PerformanceTest {
+        name: "micro_block_qcow_fsync_256_us",
+        func_ptr: micro_bench_block::micro_bench_qcow_fsync,
+        control: PerformanceTestControl {
+            test_timeout: 10,
+            test_iterations: 20,
+            warmup_iterations: 5,
+            num_ops: Some(256),
+            ..PerformanceTestControl::default()
+        },
+        unit_adjuster: adjuster::s_to_us,
+    },
 ];
 
 fn run_test_with_timeout(
diff --git a/performance-metrics/src/micro_bench_block.rs b/performance-metrics/src/micro_bench_block.rs
index 2ebde205f..30a737780 100644
--- a/performance-metrics/src/micro_bench_block.rs
+++ b/performance-metrics/src/micro_bench_block.rs
@@ -132,3 +132,33 @@ pub fn micro_bench_qcow_punch_hole(control: &PerformanceTestControl) -> f64 {
 
     elapsed
 }
+
+/// Write num_ops clusters into an empty qcow2 image to dirty L2 and
+/// refcount metadata, then time a single fsync that flushes all dirty
+/// tables to disk.
+///
+/// This isolates the metadata flush cost which scales with the number
+/// of dirty L2 table entries and refcount blocks.
+///
+/// Returns the fsync wall clock time in seconds.
+pub fn micro_bench_qcow_fsync(control: &PerformanceTestControl) -> f64 {
+    let num_ops = control.num_ops.expect("num_ops required") as usize;
+    let (_tmp, disk) = util::empty_qcow_tempfile(num_ops);
+    let mut async_io = disk.new_async_io(1).expect("new_async_io failed");
+
+    // Write num_ops clusters to dirty L2 and refcount metadata.
+    let buf = vec![0xA5u8; QCOW_CLUSTER_SIZE as usize];
+    let iovec = write_iovec(&buf);
+    submit_writes(async_io.as_mut(), num_ops, QCOW_CLUSTER_SIZE, &[iovec]);
+    // Drain write completions.
+    drain_completions(async_io.as_mut(), num_ops);
+
+    // Time the flush.
+    let start = Instant::now();
+    async_io.fsync(Some(num_ops as u64)).expect("fsync failed");
+    let elapsed = start.elapsed().as_secs_f64();
+
+    drain_completions(async_io.as_mut(), 1);
+
+    elapsed
+}