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perf(runtime): drain nextTick queue with VecDeque::pop_front (was O(n²)) #6126

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Merged
proggeramlug merged 1 commit into from
Jul 8, 2026
Merged

perf(runtime): drain nextTick queue with VecDeque::pop_front (was O(n²)) #6126

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19 changes: 7 additions & 12 deletions crates/perry-runtime/src/builtins/globals.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -958,7 +958,7 @@ fn queue_microtask_with_type(callback: i64, type_name: &str, args: Vec<f64>) {
false,
);
QUEUED_MICROTASKS.with(|q| {
q.borrow_mut().push(QueuedMicrotask {
q.borrow_mut().push_back(QueuedMicrotask {
callback,
context,
async_id: ids.async_id,
Expand All @@ -977,7 +977,9 @@ pub(crate) struct QueuedMicrotask {
}

thread_local! {
static QUEUED_MICROTASKS: std::cell::RefCell<Vec<QueuedMicrotask>> = const { std::cell::RefCell::new(Vec::new()) };
// VecDeque so the drain pops from the front in O(1); a `Vec` + `remove(0)`
// is O(n) per job → O(n²) to drain a burst of n nextTick jobs (#6084).
static QUEUED_MICROTASKS: std::cell::RefCell<std::collections::VecDeque<QueuedMicrotask>> = const { std::cell::RefCell::new(std::collections::VecDeque::new()) };
static QUEUED_MICROTASK_PREV_CONTEXTS: std::cell::RefCell<Vec<crate::async_context::AsyncContextSnapshot>> = const { std::cell::RefCell::new(Vec::new()) };
}

Expand Down Expand Up @@ -1005,14 +1007,7 @@ pub(crate) fn drain_queued_microtasks_count() -> i32 {
};
let mut ran = 0;
loop {
let task = QUEUED_MICROTASKS.with(|q| {
let mut queue = q.borrow_mut();
if queue.is_empty() {
None
} else {
Some(queue.remove(0))
}
});
let task = QUEUED_MICROTASKS.with(|q| q.borrow_mut().pop_front());
match task {
Some(QueuedMicrotask {
callback: cb,
Expand Down Expand Up @@ -1118,7 +1113,7 @@ pub(crate) fn test_seed_queued_microtask(callback: i64, context_store: f64) {
QUEUED_MICROTASKS.with(|q| {
let mut q = q.borrow_mut();
q.clear();
q.push(QueuedMicrotask {
q.push_back(QueuedMicrotask {
callback,
context,
async_id: 0,
Expand All @@ -1144,7 +1139,7 @@ pub(crate) fn test_queued_microtask_snapshot() -> (usize, u64, u64) {
QUEUED_MICROTASKS.with(|q| {
let q = q.borrow();
let (callback, store_bits) = q
.first()
.front()
.map(|task| {
(
task.callback as usize,
Expand Down
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