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Revert "Multiple priority scheduler" (#44637)

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Reverts zed-industries/zed#44575
This commit is contained in:
Yara 🏳️‍⚧️
2025-12-11 16:16:43 +01:00
committed by GitHub
parent 95dbc0efc2
commit ecb8d3d4dd
24 changed files with 154 additions and 1111 deletions
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crates/gpui/src/queue.rs
-329
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@@ -1,329 +0,0 @@
use std::{
fmt,
iter::FusedIterator,
sync::{Arc, atomic::AtomicUsize},
};
use rand::{Rng, SeedableRng, rngs::SmallRng};
use crate::Priority;
struct PriorityQueues<T> {
high_priority: Vec<T>,
medium_priority: Vec<T>,
low_priority: Vec<T>,
}
impl<T> PriorityQueues<T> {
fn is_empty(&self) -> bool {
self.high_priority.is_empty()
&& self.medium_priority.is_empty()
&& self.low_priority.is_empty()
}
}
struct PriorityQueueState<T> {
queues: parking_lot::Mutex<PriorityQueues<T>>,
condvar: parking_lot::Condvar,
receiver_count: AtomicUsize,
sender_count: AtomicUsize,
}
impl<T> PriorityQueueState<T> {
fn send(&self, priority: Priority, item: T) -> Result<(), SendError<T>> {
if self
.receiver_count
.load(std::sync::atomic::Ordering::Relaxed)
== 0
{
return Err(SendError(item));
}
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),
};
self.condvar.notify_one();
Ok(())
}
fn recv<'a>(&'a self) -> Result<parking_lot::MutexGuard<'a, PriorityQueues<T>>, RecvError> {
let mut queues = self.queues.lock();
let sender_count = self.sender_count.load(std::sync::atomic::Ordering::Relaxed);
if queues.is_empty() && sender_count == 0 {
return Err(crate::queue::RecvError);
}
// parking_lot doesn't do spurious wakeups so an if is fine
if queues.is_empty() {
self.condvar.wait(&mut queues);
}
Ok(queues)
}
fn try_recv<'a>(
&'a self,
) -> Result<Option<parking_lot::MutexGuard<'a, PriorityQueues<T>>>, RecvError> {
let mut queues = self.queues.lock();
let sender_count = self.sender_count.load(std::sync::atomic::Ordering::Relaxed);
if queues.is_empty() && sender_count == 0 {
return Err(crate::queue::RecvError);
}
if queues.is_empty() {
Ok(None)
} else {
Ok(Some(queues))
}
}
}
pub(crate) struct PriorityQueueSender<T> {
state: Arc<PriorityQueueState<T>>,
}
impl<T> PriorityQueueSender<T> {
fn new(state: Arc<PriorityQueueState<T>>) -> Self {
Self { state }
}
pub(crate) fn send(&self, priority: Priority, item: T) -> Result<(), SendError<T>> {
self.state.send(priority, item)?;
Ok(())
}
}
impl<T> Drop for PriorityQueueSender<T> {
fn drop(&mut self) {
self.state
.sender_count
.fetch_sub(1, std::sync::atomic::Ordering::AcqRel);
}
}
pub(crate) struct PriorityQueueReceiver<T> {
state: Arc<PriorityQueueState<T>>,
rand: SmallRng,
disconnected: bool,
}
impl<T> Clone for PriorityQueueReceiver<T> {
fn clone(&self) -> Self {
self.state
.receiver_count
.fetch_add(1, std::sync::atomic::Ordering::AcqRel);
Self {
state: Arc::clone(&self.state),
rand: SmallRng::seed_from_u64(0),
disconnected: self.disconnected,
}
}
}
pub(crate) struct SendError<T>(T);
impl<T: fmt::Debug> fmt::Debug for SendError<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_tuple("SendError").field(&self.0).finish()
}
}
#[derive(Debug)]
pub(crate) struct RecvError;
#[allow(dead_code)]
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(),
}),
condvar: parking_lot::Condvar::new(),
receiver_count: AtomicUsize::new(1),
sender_count: AtomicUsize::new(1),
};
let state = Arc::new(state);
let sender = PriorityQueueSender::new(Arc::clone(&state));
let receiver = PriorityQueueReceiver {
state,
rand: SmallRng::seed_from_u64(0),
disconnected: false,
};
(sender, receiver)
}
/// Tries to pop one element from the priority queue without blocking.
///
/// This will early return if there are no elements in the queue.
///
/// This method is best suited if you only intend to pop one element, for better performance
/// on large queues see [`Self::try_iter`]
///
/// # Errors
///
/// If the sender was dropped
pub(crate) fn try_pop(&mut self) -> Result<Option<T>, RecvError> {
self.pop_inner(false)
}
/// Pops an element from the priority queue blocking if necessary.
///
/// This method is best suited if you only intend to pop one element, for better performance
/// on large queues see [`Self::iter``]
///
/// # Errors
///
/// If the sender was dropped
pub(crate) fn pop(&mut self) -> Result<T, RecvError> {
self.pop_inner(true).map(|e| e.unwrap())
}
/// Returns an iterator over the elements of the queue
/// this iterator will end when all elements have been consumed and will not wait for new ones.
pub(crate) fn try_iter(self) -> TryIter<T> {
TryIter {
receiver: self,
ended: false,
}
}
/// Returns an iterator over the elements of the queue
/// this iterator will wait for new elements if the queue is empty.
pub(crate) fn iter(self) -> Iter<T> {
Iter(self)
}
#[inline(always)]
// algorithm is the loaded die from biased coin from
// https://www.keithschwarz.com/darts-dice-coins/
fn pop_inner(&mut self, block: bool) -> Result<Option<T>, RecvError> {
use Priority as P;
let mut queues = if !block {
let Some(queues) = self.state.try_recv()? else {
return Ok(None);
};
queues
} else {
self.state.recv()?
};
let high = P::High.probability() * !queues.high_priority.is_empty() as u32;
let medium = P::Medium.probability() * !queues.medium_priority.is_empty() as u32;
let low = P::Low.probability() * !queues.low_priority.is_empty() as u32;
let mut mass = high + medium + low; //%
if !queues.high_priority.is_empty() {
let flip = self.rand.random_ratio(P::High.probability(), mass);
if flip {
return Ok(queues.high_priority.pop());
}
mass -= P::High.probability();
}
if !queues.medium_priority.is_empty() {
let flip = self.rand.random_ratio(P::Medium.probability(), mass);
if flip {
return Ok(queues.medium_priority.pop());
}
mass -= P::Medium.probability();
}
if !queues.low_priority.is_empty() {
let flip = self.rand.random_ratio(P::Low.probability(), mass);
if flip {
return Ok(queues.low_priority.pop());
}
}
Ok(None)
}
}
impl<T> Drop for PriorityQueueReceiver<T> {
fn drop(&mut self) {
self.state
.receiver_count
.fetch_sub(1, std::sync::atomic::Ordering::AcqRel);
}
}
/// If None is returned the sender disconnected
pub(crate) struct Iter<T>(PriorityQueueReceiver<T>);
impl<T> Iterator for Iter<T> {
type Item = T;
fn next(&mut self) -> Option<Self::Item> {
self.0.pop_inner(true).ok().flatten()
}
}
impl<T> FusedIterator for Iter<T> {}
/// If None is returned there are no more elements in the queue
pub(crate) struct TryIter<T> {
receiver: PriorityQueueReceiver<T>,
ended: bool,
}
impl<T> Iterator for TryIter<T> {
type Item = Result<T, RecvError>;
fn next(&mut self) -> Option<Self::Item> {
if self.ended {
return None;
}
let res = self.receiver.pop_inner(false);
self.ended = res.is_err();
res.transpose()
}
}
impl<T> FusedIterator for TryIter<T> {}
#[cfg(test)]
mod tests {
use collections::HashSet;
use super::*;
#[test]
fn all_tasks_get_yielded() {
let (tx, mut rx) = PriorityQueueReceiver::new();
tx.send(Priority::Medium, 20).unwrap();
tx.send(Priority::High, 30).unwrap();
tx.send(Priority::Low, 10).unwrap();
tx.send(Priority::Medium, 21).unwrap();
tx.send(Priority::High, 31).unwrap();
drop(tx);
assert_eq!(
rx.iter().collect::<HashSet<_>>(),
[30, 31, 20, 21, 10].into_iter().collect::<HashSet<_>>()
)
}
#[test]
fn new_high_prio_task_get_scheduled_quickly() {
let (tx, mut rx) = PriorityQueueReceiver::new();
for _ in 0..100 {
tx.send(Priority::Low, 1).unwrap();
}
assert_eq!(rx.pop().unwrap(), 1);
tx.send(Priority::High, 3).unwrap();
assert_eq!(rx.pop().unwrap(), 3);
assert_eq!(rx.pop().unwrap(), 1);
}
}