From ccf855ec24db7e91af7d60d4524dcd44d25d98c2 Mon Sep 17 00:00:00 2001
From: Alice Ryhl <alice@ryhl.io>
Date: Thu, 11 Nov 2021 21:53:29 +0100
Subject: [PATCH] stats: only expose `busy_duration_total` (#4223)

---
 tokio/src/runtime/stats/stats.rs | 55 +-------------------------------
 1 file changed, 1 insertion(+), 54 deletions(-)

diff --git a/tokio/src/runtime/stats/stats.rs b/tokio/src/runtime/stats/stats.rs
index 1dc184438..b2bcaccaa 100644
--- a/tokio/src/runtime/stats/stats.rs
+++ b/tokio/src/runtime/stats/stats.rs
@@ -17,9 +17,6 @@ pub struct WorkerStats {
     park_count: AtomicU64,
     steal_count: AtomicU64,
     poll_count: AtomicU64,
-    busy_duration_min: AtomicU64,
-    busy_duration_max: AtomicU64,
-    busy_duration_last: AtomicU64,
     busy_duration_total: AtomicU64,
 }
 
@@ -31,9 +28,6 @@ impl RuntimeStats {
                 park_count: AtomicU64::new(0),
                 steal_count: AtomicU64::new(0),
                 poll_count: AtomicU64::new(0),
-                busy_duration_min: AtomicU64::new(0),
-                busy_duration_max: AtomicU64::new(0),
-                busy_duration_last: AtomicU64::new(0),
                 busy_duration_total: AtomicU64::new(0),
             });
         }
@@ -66,25 +60,10 @@ impl WorkerStats {
         self.poll_count.load(Relaxed)
     }
 
-    /// Returns the duration for which the runtime was busy last time it was busy.
-    pub fn busy_duration_last(&self) -> Duration {
-        Duration::from_nanos(self.busy_duration_last.load(Relaxed))
-    }
-
     /// Returns the total amount of time this worker has been busy for.
-    pub fn busy_duration_total(&self) -> Duration {
+    pub fn total_busy_duration(&self) -> Duration {
         Duration::from_nanos(self.busy_duration_total.load(Relaxed))
     }
-
-    /// Returns the smallest busy duration since the last 16 parks.
-    pub fn busy_duration_min(&self) -> Duration {
-        Duration::from_nanos(self.busy_duration_min.load(Relaxed))
-    }
-
-    /// Returns the largest busy duration since the last 16 parks.
-    pub fn busy_duration_max(&self) -> Duration {
-        Duration::from_nanos(self.busy_duration_max.load(Relaxed))
-    }
 }
 
 pub(crate) struct WorkerStatsBatcher {
@@ -92,13 +71,6 @@ pub(crate) struct WorkerStatsBatcher {
     park_count: u64,
     steal_count: u64,
     poll_count: u64,
-    /// The last 16 busy durations in nanoseconds.
-    ///
-    /// This array is set to contain the same value 16 times after the first
-    /// iteration. Since we only publish the min, max and last value in the
-    /// array, then this gives the correct result.
-    busy_duration: [u64; 16],
-    busy_duration_i: usize,
     /// The total busy duration in nanoseconds.
     busy_duration_total: u64,
     last_resume_time: Instant,
@@ -111,8 +83,6 @@ impl WorkerStatsBatcher {
             park_count: 0,
             steal_count: 0,
             poll_count: 0,
-            busy_duration: [0; 16],
-            busy_duration_i: usize::MAX,
             busy_duration_total: 0,
             last_resume_time: Instant::now(),
         }
@@ -124,20 +94,6 @@ impl WorkerStatsBatcher {
         worker.steal_count.store(self.steal_count, Relaxed);
         worker.poll_count.store(self.poll_count, Relaxed);
 
-        let mut min = u64::MAX;
-        let mut max = 0;
-        let last = self.busy_duration[self.busy_duration_i % 16];
-        for &val in &self.busy_duration {
-            if val <= min {
-                min = val;
-            }
-            if val >= max {
-                max = val;
-            }
-        }
-        worker.busy_duration_min.store(min, Relaxed);
-        worker.busy_duration_max.store(max, Relaxed);
-        worker.busy_duration_last.store(last, Relaxed);
         worker
             .busy_duration_total
             .store(self.busy_duration_total, Relaxed);
@@ -149,15 +105,6 @@ impl WorkerStatsBatcher {
         let busy_duration = self.last_resume_time.elapsed();
         let busy_duration = u64::try_from(busy_duration.as_nanos()).unwrap_or(u64::MAX);
         self.busy_duration_total += busy_duration;
-        if self.busy_duration_i == usize::MAX {
-            // We are parking for the first time. Set array to contain current
-            // duration in every slot.
-            self.busy_duration_i = 0;
-            self.busy_duration = [busy_duration; 16];
-        } else {
-            self.busy_duration_i = (self.busy_duration_i + 1) % 16;
-            self.busy_duration[self.busy_duration_i] = busy_duration;
-        }
     }
 
     pub(crate) fn returned_from_park(&mut self) {