adjusted scheduler prioritization algorithm (#45367)

Yara 🏳️‍⚧️ created 1 week ago

This fixes a number of issues where zed depends on the order of polling which changed when switching scheduler. We have adjusted the algorithm so it matches the previous order while keeping the prioritization feature.

Release Notes:
- N/A

Change summary

crates/gpui/src/queue.rs | 25 +++++++++++++------------
1 file changed, 13 insertions(+), 12 deletions(-)

Detailed changes

crates/gpui/src/queue.rs

@@ -1,4 +1,5 @@
 use std::{
+    collections::VecDeque,
     fmt,
     iter::FusedIterator,
     sync::{Arc, atomic::AtomicUsize},
@@ -9,9 +10,9 @@ use rand::{Rng, SeedableRng, rngs::SmallRng};
 use crate::Priority;
 
 struct PriorityQueues<T> {
-    high_priority: Vec<T>,
-    medium_priority: Vec<T>,
-    low_priority: Vec<T>,
+    high_priority: VecDeque<T>,
+    medium_priority: VecDeque<T>,
+    low_priority: VecDeque<T>,
 }
 
 impl<T> PriorityQueues<T> {
@@ -42,9 +43,9 @@ impl<T> PriorityQueueState<T> {
         let mut queues = self.queues.lock();
         match priority {
             Priority::Realtime(_) => unreachable!(),
-            Priority::High => queues.high_priority.push(item),
-            Priority::Medium => queues.medium_priority.push(item),
-            Priority::Low => queues.low_priority.push(item),
+            Priority::High => queues.high_priority.push_back(item),
+            Priority::Medium => queues.medium_priority.push_back(item),
+            Priority::Low => queues.low_priority.push_back(item),
         };
         self.condvar.notify_one();
         Ok(())
@@ -141,9 +142,9 @@ impl<T> PriorityQueueReceiver<T> {
     pub(crate) fn new() -> (PriorityQueueSender<T>, Self) {
         let state = PriorityQueueState {
             queues: parking_lot::Mutex::new(PriorityQueues {
-                high_priority: Vec::new(),
-                medium_priority: Vec::new(),
-                low_priority: Vec::new(),
+                high_priority: VecDeque::new(),
+                medium_priority: VecDeque::new(),
+                low_priority: VecDeque::new(),
             }),
             condvar: parking_lot::Condvar::new(),
             receiver_count: AtomicUsize::new(1),
@@ -226,7 +227,7 @@ impl<T> PriorityQueueReceiver<T> {
         if !queues.high_priority.is_empty() {
             let flip = self.rand.random_ratio(P::High.probability(), mass);
             if flip {
-                return Ok(queues.high_priority.pop());
+                return Ok(queues.high_priority.pop_front());
             }
             mass -= P::High.probability();
         }
@@ -234,7 +235,7 @@ impl<T> PriorityQueueReceiver<T> {
         if !queues.medium_priority.is_empty() {
             let flip = self.rand.random_ratio(P::Medium.probability(), mass);
             if flip {
-                return Ok(queues.medium_priority.pop());
+                return Ok(queues.medium_priority.pop_front());
             }
             mass -= P::Medium.probability();
         }
@@ -242,7 +243,7 @@ impl<T> PriorityQueueReceiver<T> {
         if !queues.low_priority.is_empty() {
             let flip = self.rand.random_ratio(P::Low.probability(), mass);
             if flip {
-                return Ok(queues.low_priority.pop());
+                return Ok(queues.low_priority.pop_front());
             }
         }