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Added a bloom filter to CSS selector matching.

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This commit is contained in:
Clark Gaebel 2014-09-02 10:16:11 -07:00
parent d161d0ad47
commit acd83ff47b
20 changed files with 817 additions and 78 deletions
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133
components/layout/parallel.rs
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@ -20,12 +20,14 @@ use wrapper::{layout_node_to_unsafe_layout_node, layout_node_from_unsafe_layout_
use wrapper::{ThreadSafeLayoutNode, UnsafeLayoutNode};
use gfx::display_list::OpaqueNode;
use servo_util::bloom::BloomFilter;
use servo_util::time::{TimeProfilerChan, profile};
use servo_util::time;
use servo_util::workqueue::{WorkQueue, WorkUnit, WorkerProxy};
use std::mem;
use std::ptr;
use std::sync::atomics::{AtomicInt, Relaxed, SeqCst};
use style;
use style::TNode;
#[allow(dead_code)]
@ -213,7 +215,91 @@ impl<'a> ParallelPreorderFlowTraversal for AssignISizesTraversal<'a> {
impl<'a> ParallelPostorderFlowTraversal for AssignBSizesAndStoreOverflowTraversal<'a> {}
fn recalc_style_for_node(unsafe_layout_node: UnsafeLayoutNode,
/// A pair of the bloom filter used for css selector matching, and the node to
/// which it applies. This is used to efficiently do `Descendant` selector
/// matches. Thanks to the bloom filter, we can avoid walking up the tree
/// looking for ancestors that aren't there in the majority of cases.
///
/// As we walk down the DOM tree a task-local bloom filter is built of all the
/// CSS `SimpleSelector`s which are part of a `Descendant` compound selector
/// (i.e. paired with a `Descendant` combinator, in the `next` field of a
/// `CompoundSelector`.
///
/// Before a `Descendant` selector match is tried, it's compared against the
/// bloom filter. If the bloom filter can exclude it, the selector is quickly
/// rejected.
///
/// When done styling a node, all selectors previously inserted into the filter
/// are removed.
///
/// Since a work-stealing queue is used for styling, sometimes, the bloom filter
/// will no longer be the for the parent of the node we're currently on. When
/// this happens, the task local bloom filter will be thrown away and rebuilt.
local_data_key!(style_bloom: (BloomFilter, UnsafeLayoutNode))
/// Returns the task local bloom filter.
///
/// If one does not exist, a new one will be made for you. If it is out of date,
/// it will be thrown out and a new one will be made for you.
fn take_task_local_bloom_filter(
parent_node: Option<LayoutNode>,
layout_context: &LayoutContext)
-> BloomFilter {
let new_bloom =
|p: Option<LayoutNode>| -> BloomFilter {
let mut bf = BloomFilter::new(style::RECOMMENDED_SELECTOR_BLOOM_FILTER_SIZE);
p.map(|p| insert_ancestors_into_bloom_filter(&mut bf, p, layout_context));
bf
};
match (parent_node, style_bloom.replace(None)) {
// Root node. Needs new bloom filter.
(None, _ ) => new_bloom(None),
// No bloom filter for this thread yet.
(Some(p), None) => new_bloom(Some(p)),
// Found cached bloom filter.
(Some(p), Some((bf, old_node))) => {
// Hey, the cached parent is our parent! We can reuse the bloom filter.
if old_node == layout_node_to_unsafe_layout_node(&p) {
bf
// Oh no. the cached parent is stale. I guess we need a new one...
} else {
new_bloom(Some(p))
}
},
}
}
fn put_task_local_bloom_filter(bf: BloomFilter, unsafe_node: &UnsafeLayoutNode) {
match style_bloom.replace(Some((bf, *unsafe_node))) {
None => {},
Some(_) => fail!("Putting into a never-taken task-local bloom filter"),
}
}
/// "Ancestors" in this context is inclusive of ourselves.
fn insert_ancestors_into_bloom_filter(
bf: &mut BloomFilter, mut n: LayoutNode, layout_context: &LayoutContext) {
loop {
n.insert_into_bloom_filter(bf);
n = match parent_node(&n, layout_context) {
None => return,
Some(p) => p,
};
}
}
fn parent_node<'ln>(node: &LayoutNode<'ln>, layout_context: &LayoutContext) -> Option<LayoutNode<'ln>> {
let opaque_node: OpaqueNode = OpaqueNodeMethods::from_layout_node(node);
if opaque_node == layout_context.shared.reflow_root {
None
} else {
node.parent_node()
}
}
fn recalc_style_for_node(mut unsafe_layout_node: UnsafeLayoutNode,
proxy: &mut WorkerProxy<*const SharedLayoutContext,UnsafeLayoutNode>) {
let shared_layout_context = unsafe { &**proxy.user_data() };
let layout_context = LayoutContext::new(shared_layout_context);
@ -230,12 +316,10 @@ fn recalc_style_for_node(unsafe_layout_node: UnsafeLayoutNode,
node.initialize_layout_data(layout_context.shared.layout_chan.clone());
// Get the parent node.
let opaque_node: OpaqueNode = OpaqueNodeMethods::from_layout_node(&node);
let parent_opt = if opaque_node == layout_context.shared.reflow_root {
None
} else {
node.parent_node()
};
let parent_opt = parent_node(&node, &layout_context);
// Get the style bloom filter.
let bf = take_task_local_bloom_filter(parent_opt, &layout_context);
// First, check to see whether we can share a style with someone.
let style_sharing_candidate_cache = layout_context.style_sharing_candidate_cache();
@ -244,6 +328,9 @@ fn recalc_style_for_node(unsafe_layout_node: UnsafeLayoutNode,
parent_opt.clone())
};
// Just needs to be wrapped in an option for `match_node`.
let some_bf = Some(bf);
// Otherwise, match and cascade selectors.
match sharing_result {
CannotShare(mut shareable) => {
@ -252,7 +339,7 @@ fn recalc_style_for_node(unsafe_layout_node: UnsafeLayoutNode,
if node.is_element() {
// Perform the CSS selector matching.
let stylist = unsafe { &*layout_context.shared.stylist };
node.match_node(stylist, &mut applicable_declarations, &mut shareable);
node.match_node(stylist, &some_bf, &mut applicable_declarations, &mut shareable);
}
// Perform the CSS cascade.
@ -285,6 +372,13 @@ fn recalc_style_for_node(unsafe_layout_node: UnsafeLayoutNode,
}
}
// It can be `None` now.
let mut bf = some_bf;
// Before running the children, we need to insert our nodes into the bloom
// filter.
bf.as_mut().map(|bf| node.insert_into_bloom_filter(bf));
// It's *very* important that this block is in a separate scope to the block above,
// to avoid a data race that can occur (github issue #2308). The block above issues
// a borrow on the node layout data. That borrow must be dropped before the child
@ -299,19 +393,21 @@ fn recalc_style_for_node(unsafe_layout_node: UnsafeLayoutNode,
data: layout_node_to_unsafe_layout_node(&kid),
});
}
return
} else {
// If we got here, we're a leaf. Start construction of flows for this node.
construct_flows(&mut unsafe_layout_node, &mut bf, &layout_context);
}
// If we got here, we're a leaf. Start construction of flows for this node.
construct_flows(unsafe_layout_node, &layout_context)
bf.map(|bf| put_task_local_bloom_filter(bf, &unsafe_layout_node));
}
fn construct_flows(mut unsafe_layout_node: UnsafeLayoutNode,
layout_context: &LayoutContext) {
fn construct_flows<'a>(unsafe_layout_node: &mut UnsafeLayoutNode,
parent_bf: &mut Option<BloomFilter>,
layout_context: &'a LayoutContext<'a>) {
loop {
// Get a real layout node.
let node: LayoutNode = unsafe {
layout_node_from_unsafe_layout_node(&unsafe_layout_node)
layout_node_from_unsafe_layout_node(&*unsafe_layout_node)
};
// Construct flows for this node.
@ -340,7 +436,10 @@ fn construct_flows(mut unsafe_layout_node: UnsafeLayoutNode,
// If this is the reflow root, we're done.
let opaque_node: OpaqueNode = OpaqueNodeMethods::from_layout_node(&node);
if layout_context.shared.reflow_root == opaque_node {
break
*parent_bf = None;
break;
} else {
parent_bf.as_mut().map(|parent_bf| node.remove_from_bloom_filter(parent_bf));
}
// Otherwise, enqueue the parent.
@ -352,6 +451,8 @@ fn construct_flows(mut unsafe_layout_node: UnsafeLayoutNode,
unsafe {
match *parent.borrow_layout_data_unchecked() {
Some(ref parent_layout_data) => {
*unsafe_layout_node = layout_node_to_unsafe_layout_node(&parent);
let parent_layout_data: &mut LayoutDataWrapper = mem::transmute(parent_layout_data);
if parent_layout_data.data
.parallel
@ -359,7 +460,6 @@ fn construct_flows(mut unsafe_layout_node: UnsafeLayoutNode,
.fetch_sub(1, SeqCst) == 1 {
// We were the last child of our parent. Construct flows for our
// parent.
unsafe_layout_node = layout_node_to_unsafe_layout_node(&parent)
} else {
// Get out of here and find another node to work on.
break
@ -558,4 +658,3 @@ pub fn build_display_list_for_subtree(root: &mut FlowRef,
queue.data = ptr::null()
}