diff --git a/pageserver/src/metrics.rs b/pageserver/src/metrics.rs
index 983a3079e4..6a5dc3e749 100644
--- a/pageserver/src/metrics.rs
+++ b/pageserver/src/metrics.rs
@@ -1439,27 +1439,43 @@ impl Drop for SmgrOpTimer {
 }
 
 impl SmgrOpFlushInProgress {
-    pub(crate) async fn measure<Fut, O>(self, mut started_at: Instant, mut fut: Fut) -> O
+    pub(crate) async fn measure<Fut, O>(self, started_at: Instant, mut fut: Fut) -> O
     where
         Fut: std::future::Future<Output = O>,
     {
         let mut fut = std::pin::pin!(fut);
 
-        // Whenever observe_guard gets called, or dropped,
-        // it adds the time elapsed since its last call to metrics.
-        // Last call is tracked in `now`.
+        let mut logged = false;
+        let mut last_counter_increment_at = started_at;
         let mut observe_guard = scopeguard::guard(
-            || {
+            |is_timeout| {
                 let now = Instant::now();
-                let elapsed = now - started_at;
-                self.global_micros
-                    .inc_by(u64::try_from(elapsed.as_micros()).unwrap());
-                self.per_timeline_micros
-                    .inc_by(u64::try_from(elapsed.as_micros()).unwrap());
-                started_at = now;
+
+                // Increment counter
+                {
+                    let elapsed_since_last_observe = now - last_counter_increment_at;
+                    self.global_micros
+                        .inc_by(u64::try_from(elapsed_since_last_observe.as_micros()).unwrap());
+                    self.per_timeline_micros
+                        .inc_by(u64::try_from(elapsed_since_last_observe.as_micros()).unwrap());
+                    last_counter_increment_at = now;
+                }
+
+                // Log something on every timeout, and on completion but only if we hit a timeout.
+                if is_timeout || logged {
+                    logged = true;
+                    let elapsed_total = now - started_at;
+                    let msg = if is_timeout {
+                        "slow flush ongoing"
+                    } else {
+                        "slow flush completed or cancelled"
+                    };
+                    let elapsed_total_secs = format!("{:.6}", elapsed_total.as_secs_f64());
+                    tracing::info!(elapsed_total_secs, msg);
+                }
             },
             |mut observe| {
-                observe();
+                observe(false);
             },
         );
 
@@ -1467,7 +1483,7 @@ impl SmgrOpFlushInProgress {
             match tokio::time::timeout(Duration::from_secs(10), &mut fut).await {
                 Ok(v) => return v,
                 Err(_timeout) => {
-                    (*observe_guard)();
+                    (*observe_guard)(true);
                 }
             }
         }