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Don't do recursive tail calls if there's work in the queue.

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MozReview-Commit-ID: 8JEdjqAIYmQ
This commit is contained in:
Bobby Holley 2017-06-08 16:25:43 -07:00
parent ce19c949db
commit f04c25c33c
1 changed files with 24 additions and 29 deletions
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53
components/style/parallel.rs
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@ -50,7 +50,7 @@ type NodeList<N> = SmallVec<[SendNode<N>; WORK_UNIT_MAX]>;
pub fn traverse_dom<E, D>(traversal: &D,
root: E,
token: PreTraverseToken,
queue: &rayon::ThreadPool)
pool: &rayon::ThreadPool)
where E: TElement,
D: DomTraversal<E>,
{
@ -82,16 +82,17 @@ pub fn traverse_dom<E, D>(traversal: &D,
let traversal_data = PerLevelTraversalData {
current_dom_depth: depth,
};
let tls = ScopedTLS::<D::ThreadLocalContext>::new(queue);
let tls = ScopedTLS::<D::ThreadLocalContext>::new(pool);
let root = root.as_node().opaque();
queue.install(|| {
pool.install(|| {
rayon::scope(|scope| {
traverse_nodes(nodes,
DispatchMode::TailCall,
root,
traversal_data,
scope,
pool,
traversal,
&tls);
});
@ -144,6 +145,7 @@ fn top_down_dom<'a, 'scope, E, D>(nodes: &'a [SendNode<E::ConcreteNode>],
root: OpaqueNode,
mut traversal_data: PerLevelTraversalData,
scope: &'a rayon::Scope<'scope>,
pool: &'scope rayon::ThreadPool,
traversal: &'scope D,
tls: &'scope ScopedTLS<'scope, D::ThreadLocalContext>)
where E: TElement + 'scope,
@ -179,6 +181,7 @@ fn top_down_dom<'a, 'scope, E, D>(nodes: &'a [SendNode<E::ConcreteNode>],
root,
traversal_data_copy,
scope,
pool,
traversal,
tls);
}
@ -208,6 +211,7 @@ fn top_down_dom<'a, 'scope, E, D>(nodes: &'a [SendNode<E::ConcreteNode>],
root,
traversal_data,
scope,
pool,
traversal,
tls);
}
@ -231,6 +235,7 @@ fn traverse_nodes<'a, 'scope, E, D>(nodes: NodeList<E::ConcreteNode>,
root: OpaqueNode,
traversal_data: PerLevelTraversalData,
scope: &'a rayon::Scope<'scope>,
pool: &'scope rayon::ThreadPool,
traversal: &'scope D,
tls: &'scope ScopedTLS<'scope, D::ThreadLocalContext>)
where E: TElement + 'scope,
@ -238,42 +243,32 @@ fn traverse_nodes<'a, 'scope, E, D>(nodes: NodeList<E::ConcreteNode>,
{
debug_assert!(!nodes.is_empty());
// This is a tail call from the perspective of the caller. However, we only
// want to actually dispatch the job as a tail call if there's nothing left
// in our local queue. Otherwise we need to return to it to maintain proper
// breadth-first ordering.
let may_dispatch_tail = mode.is_tail_call() &&
!pool.current_thread_has_pending_tasks().unwrap();
// In the common case, our children fit within a single work unit, in which
// case we can pass the SmallVec directly and avoid extra allocation.
if nodes.len() <= WORK_UNIT_MAX {
if mode.is_tail_call() {
// If this is a tail call, bypass rayon and invoke top_down_dom directly.
top_down_dom(&nodes, root, traversal_data, scope, traversal, tls);
if may_dispatch_tail {
top_down_dom(&nodes, root, traversal_data, scope, pool, traversal, tls);
} else {
// The caller isn't done yet. Append to the queue and return synchronously.
scope.spawn(move |scope| {
let nodes = nodes;
top_down_dom(&nodes, root, traversal_data, scope, traversal, tls);
top_down_dom(&nodes, root, traversal_data, scope, pool, traversal, tls);
});
}
} else {
// FIXME(bholley): This should be an ArrayVec.
let mut first_chunk: Option<NodeList<E::ConcreteNode>> = None;
for chunk in nodes.chunks(WORK_UNIT_MAX) {
if mode.is_tail_call() && first_chunk.is_none() {
first_chunk = Some(chunk.iter().cloned().collect::<NodeList<E::ConcreteNode>>());
} else {
let boxed = chunk.iter().cloned().collect::<Vec<_>>().into_boxed_slice();
let traversal_data_copy = traversal_data.clone();
scope.spawn(move |scope| {
let b = boxed;
top_down_dom(&*b, root, traversal_data_copy, scope, traversal, tls)
});
}
}
// If this is a tail call, bypass rayon for the first chunk and invoke top_down_dom
// directly.
debug_assert_eq!(first_chunk.is_some(), mode.is_tail_call());
if let Some(c) = first_chunk {
debug_assert_eq!(c.len(), WORK_UNIT_MAX);
top_down_dom(&*c, root, traversal_data, scope, traversal, tls);
let boxed = chunk.iter().cloned().collect::<Vec<_>>().into_boxed_slice();
let traversal_data_copy = traversal_data.clone();
scope.spawn(move |scope| {
let b = boxed;
top_down_dom(&*b, root, traversal_data_copy, scope, pool, traversal, tls)
});
}
}
}