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Rewrite the style sharing candidate cache.

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The style candidate cache had regressed a few times (see #12534), and my
intuition is that being able to disable all style sharing with a single rule in
the page is really unfortunate.

This commit redesigns the style sharing cache in order to be a optimistic cache,
but then reject candidates if they match different sibling-affecting selectors
in the page, for example.

So far the numbers have improved, but not so much as I'd wanted (~10%/20% of
non-incremental restyling time in general). The current implementation is really
dumb though (we recompute and re-match a lot of stuff), so we should be able to
optimise it quite a bit.

I have different ideas for improving it (that may or may not work), apart of the
low-hanging fruit like don't re-matching candidates all the time but I have to
measure the real impact.

Also, I need to verify it against try.
This commit is contained in:
Emilio Cobos Álvarez 2016-07-29 17:24:12 -07:00
parent ec53136863
commit 3af774bd75
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GPG key ID: 056B727BB9C1027C
23 changed files with 467 additions and 236 deletions
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159
components/style/selector_matching.rs
View file

@ -15,7 +15,9 @@ use selector_impl::{ElementExt, TheSelectorImpl, PseudoElement};
use selectors::Element;
use selectors::bloom::BloomFilter;
use selectors::matching::DeclarationBlock as GenericDeclarationBlock;
use selectors::matching::{Rule, SelectorMap};
use selectors::matching::{AFFECTED_BY_STYLE_ATTRIBUTE, AFFECTED_BY_PRESENTATIONAL_HINTS};
use selectors::matching::{Rule, SelectorMap, StyleRelations};
use selectors::parser::Selector;
use sink::Push;
use smallvec::VecLike;
use std::collections::HashMap;
@ -26,7 +28,6 @@ use style_traits::viewport::ViewportConstraints;
use stylesheets::{CSSRule, CSSRuleIteratorExt, Origin, Stylesheet};
use viewport::{MaybeNew, ViewportRuleCascade};
pub type DeclarationBlock = GenericDeclarationBlock<Vec<PropertyDeclaration>>;
/// This structure holds all the selectors and device characteristics
@ -76,6 +77,13 @@ pub struct Stylist {
/// Selector dependencies used to compute restyle hints.
state_deps: DependencySet,
/// Selectors in the page affecting siblings
sibling_affecting_selectors: Vec<Selector<TheSelectorImpl>>,
/// Selectors in the page matching elements with non-common style-affecting
/// attributes.
non_common_style_affecting_attributes_selectors: Vec<Selector<TheSelectorImpl>>,
}
impl Stylist {
@ -93,6 +101,10 @@ impl Stylist {
precomputed_pseudo_element_decls: HashMap::with_hasher(Default::default()),
rules_source_order: 0,
state_deps: DependencySet::new(),
// XXX remember resetting them!
sibling_affecting_selectors: vec![],
non_common_style_affecting_attributes_selectors: vec![]
};
TheSelectorImpl::each_eagerly_cascaded_pseudo_element(|pseudo| {
@ -120,6 +132,9 @@ impl Stylist {
self.rules_source_order = 0;
self.state_deps.clear();
self.sibling_affecting_selectors.clear();
self.non_common_style_affecting_attributes_selectors.clear();
for ref stylesheet in TheSelectorImpl::get_user_or_user_agent_stylesheets().iter() {
self.add_stylesheet(&stylesheet);
}
@ -178,8 +193,16 @@ impl Stylist {
append!(style_rule, normal);
append!(style_rule, important);
rules_source_order += 1;
for selector in &style_rule.selectors {
self.state_deps.note_selector(selector.compound_selectors.clone());
self.state_deps.note_selector(&selector.compound_selectors);
if selector.affects_siblings() {
self.sibling_affecting_selectors.push(selector.clone());
}
if selector.matches_non_common_style_affecting_attribute() {
self.non_common_style_affecting_attributes_selectors.push(selector.clone());
}
}
self.rules_source_order = rules_source_order;
@ -202,6 +225,14 @@ impl Stylist {
}
}
debug!("Stylist stats:");
debug!(" - Got {} sibling-affecting selectors",
self.sibling_affecting_selectors.len());
debug!(" - Got {} non-common-style-attribute-affecting selectors",
self.non_common_style_affecting_attributes_selectors.len());
debug!(" - Got {} deps for style-hint calculation",
self.state_deps.len());
TheSelectorImpl::each_precomputed_pseudo_element(|pseudo| {
// TODO: Consider not doing this and just getting the rules on the
// fly. It should be a bit slower, but we'd take rid of the
@ -310,11 +341,11 @@ impl Stylist {
parent_bf: Option<&BloomFilter>,
style_attribute: Option<&PropertyDeclarationBlock>,
pseudo_element: Option<&PseudoElement>,
applicable_declarations: &mut V)
-> bool
where E: Element<Impl=TheSelectorImpl> +
PresentationalHintsSynthetizer,
V: Push<DeclarationBlock> + VecLike<DeclarationBlock> {
applicable_declarations: &mut V) -> StyleRelations
where E: Element<Impl=TheSelectorImpl> +
PresentationalHintsSynthetizer,
V: Push<DeclarationBlock> + VecLike<DeclarationBlock>
{
assert!(!self.is_device_dirty);
assert!(style_attribute.is_none() || pseudo_element.is_none(),
"Style attributes do not apply to pseudo-elements");
@ -327,65 +358,82 @@ impl Stylist {
None => &self.element_map,
};
let mut shareable = true;
let mut relations = StyleRelations::empty();
debug!("Determining if style is shareable: pseudo: {}", pseudo_element.is_some());
// Step 1: Normal user-agent rules.
map.user_agent.normal.get_all_matching_rules(element,
parent_bf,
applicable_declarations,
&mut shareable);
&mut relations);
debug!("UA normal: {:?}", relations);
// Step 2: Presentational hints.
let length = applicable_declarations.len();
element.synthesize_presentational_hints_for_legacy_attributes(applicable_declarations);
if applicable_declarations.len() != length {
// Never share style for elements with preshints
shareable = false;
relations |= AFFECTED_BY_PRESENTATIONAL_HINTS;
}
debug!("preshints: {:?}", relations);
// Step 3: User and author normal rules.
map.user.normal.get_all_matching_rules(element,
parent_bf,
applicable_declarations,
&mut shareable);
&mut relations);
debug!("user normal: {:?}", relations);
map.author.normal.get_all_matching_rules(element,
parent_bf,
applicable_declarations,
&mut shareable);
&mut relations);
debug!("author normal: {:?}", relations);
// Step 4: Normal style attributes.
style_attribute.map(|sa| {
shareable = false;
if let Some(ref sa) = style_attribute {
relations |= AFFECTED_BY_STYLE_ATTRIBUTE;
Push::push(
applicable_declarations,
GenericDeclarationBlock::from_declarations(sa.normal.clone()))
});
GenericDeclarationBlock::from_declarations(sa.normal.clone()));
}
debug!("style attr: {:?}", relations);
// Step 5: Author-supplied `!important` rules.
map.author.important.get_all_matching_rules(element,
parent_bf,
applicable_declarations,
&mut shareable);
&mut relations);
debug!("author important: {:?}", relations);
// Step 6: `!important` style attributes.
style_attribute.map(|sa| {
shareable = false;
if let Some(ref sa) = style_attribute {
Push::push(
applicable_declarations,
GenericDeclarationBlock::from_declarations(sa.important.clone()))
});
GenericDeclarationBlock::from_declarations(sa.important.clone()));
}
debug!("style attr important: {:?}", relations);
// Step 7: User and UA `!important` rules.
map.user.important.get_all_matching_rules(element,
parent_bf,
applicable_declarations,
&mut shareable);
&mut relations);
debug!("user important: {:?}", relations);
map.user_agent.important.get_all_matching_rules(element,
parent_bf,
applicable_declarations,
&mut shareable);
&mut relations);
shareable
debug!("UA important: {:?}", relations);
debug!("push_applicable_declarations: shareable: {:?}", relations);
relations
}
#[inline]
@ -398,6 +446,67 @@ impl Stylist {
&self.animations
}
pub fn match_same_not_common_style_affecting_attributes_rules<E>(&self,
element: &E,
candidate: &E) -> bool
where E: ElementExt
{
use selectors::matching::StyleRelations;
use selectors::matching::matches_compound_selector;
// XXX we can probably do better, the candidate should already know what
// rules it matches.
//
// XXX Could the bloom filter help here? Should be available.
for ref selector in self.non_common_style_affecting_attributes_selectors.iter() {
let element_matches = matches_compound_selector(&selector.compound_selectors,
element,
None,
&mut StyleRelations::empty());
let candidate_matches = matches_compound_selector(&selector.compound_selectors,
candidate,
None,
&mut StyleRelations::empty());
if element_matches != candidate_matches {
return false;
}
}
true
}
pub fn match_same_sibling_affecting_rules<E>(&self,
element: &E,
candidate: &E) -> bool
where E: ElementExt
{
use selectors::matching::StyleRelations;
use selectors::matching::matches_compound_selector;
// XXX we can probably do better, the candidate should already know what
// rules it matches.
//
// XXX The bloom filter would help here, and should be available.
for ref selector in self.sibling_affecting_selectors.iter() {
let element_matches = matches_compound_selector(&selector.compound_selectors,
element,
None,
&mut StyleRelations::empty());
let candidate_matches = matches_compound_selector(&selector.compound_selectors,
candidate,
None,
&mut StyleRelations::empty());
if element_matches != candidate_matches {
debug!("match_same_sibling_affecting_rules: Failure due to {:?}",
selector.compound_selectors);
return false;
}
}
true
}
pub fn compute_restyle_hint<E>(&self, element: &E,
snapshot: &E::Snapshot,
// NB: We need to pass current_state as an argument because