Split TraversalStatistics into two parts.

components/style/context.rs

@@ -296,7 +296,7 @@ impl ElementCascadeInputs {
 /// thread and then combine them after the threads join via the Add
 /// implementation below.
 #[derive(Default)]
-pub struct TraversalStatistics {
+pub struct PerThreadTraversalStatistics {
     /// The total number of elements traversed.
     pub elements_traversed: u32,
     /// The number of elements where has_styles() went from false to true.
@@ -308,6 +308,28 @@ pub struct TraversalStatistics {
     /// The number of styles reused via rule node comparison from the
     /// StyleSharingCache.
     pub styles_reused: u32,
+}
+
+/// Implementation of Add to aggregate statistics across different threads.
+impl<'a> ops::Add for &'a PerThreadTraversalStatistics {
+    type Output = PerThreadTraversalStatistics;
+    fn add(self, other: Self) -> PerThreadTraversalStatistics {
+        PerThreadTraversalStatistics {
+            elements_traversed: self.elements_traversed + other.elements_traversed,
+            elements_styled: self.elements_styled + other.elements_styled,
+            elements_matched: self.elements_matched + other.elements_matched,
+            styles_shared: self.styles_shared + other.styles_shared,
+            styles_reused: self.styles_reused + other.styles_reused,
+        }
+    }
+}
+
+/// Statistics gathered during the traversal plus some information from
+/// other sources including stylist.
+#[derive(Default)]
+pub struct TraversalStatistics {
+    /// Aggregated statistics gathered during the traversal.
+    pub aggregated: PerThreadTraversalStatistics,
     /// The number of selectors in the stylist.
     pub selectors: u32,
     /// The number of revalidation selectors.
@@ -321,38 +343,9 @@ pub struct TraversalStatistics {
     /// Time spent in the traversal, in milliseconds.
     pub traversal_time_ms: f64,
     /// Whether this was a parallel traversal.
-    pub is_parallel: Option<bool>,
+    pub is_parallel: bool,
     /// Whether this is a "large" traversal.
-    pub is_large: Option<bool>,
+    pub is_large: bool,
-}
-
-/// Implementation of Add to aggregate statistics across different threads.
-impl<'a> ops::Add for &'a TraversalStatistics {
-    type Output = TraversalStatistics;
-    fn add(self, other: Self) -> TraversalStatistics {
-        debug_assert!(self.traversal_time_ms == 0.0 && other.traversal_time_ms == 0.0,
-                      "traversal_time_ms should be set at the end by the caller");
-        debug_assert!(self.selectors == 0, "set at the end");
-        debug_assert!(self.revalidation_selectors == 0, "set at the end");
-        debug_assert!(self.dependency_selectors == 0, "set at the end");
-        debug_assert!(self.declarations == 0, "set at the end");
-        debug_assert!(self.stylist_rebuilds == 0, "set at the end");
-        TraversalStatistics {
-            elements_traversed: self.elements_traversed + other.elements_traversed,
-            elements_styled: self.elements_styled + other.elements_styled,
-            elements_matched: self.elements_matched + other.elements_matched,
-            styles_shared: self.styles_shared + other.styles_shared,
-            styles_reused: self.styles_reused + other.styles_reused,
-            selectors: 0,
-            revalidation_selectors: 0,
-            dependency_selectors: 0,
-            declarations: 0,
-            stylist_rebuilds: 0,
-            traversal_time_ms: 0.0,
-            is_parallel: None,
-            is_large: None,
-        }
-    }
 }
 
 /// Format the statistics in a way that the performance test harness understands.
@@ -361,16 +354,16 @@ impl fmt::Display for TraversalStatistics {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         debug_assert!(self.traversal_time_ms != 0.0, "should have set traversal time");
         writeln!(f, "[PERF] perf block start")?;
-        writeln!(f, "[PERF],traversal,{}", if self.is_parallel.unwrap() {
+        writeln!(f, "[PERF],traversal,{}", if self.is_parallel {
             "parallel"
         } else {
             "sequential"
         })?;
-        writeln!(f, "[PERF],elements_traversed,{}", self.elements_traversed)?;
+        writeln!(f, "[PERF],elements_traversed,{}", self.aggregated.elements_traversed)?;
-        writeln!(f, "[PERF],elements_styled,{}", self.elements_styled)?;
+        writeln!(f, "[PERF],elements_styled,{}", self.aggregated.elements_styled)?;
-        writeln!(f, "[PERF],elements_matched,{}", self.elements_matched)?;
+        writeln!(f, "[PERF],elements_matched,{}", self.aggregated.elements_matched)?;
-        writeln!(f, "[PERF],styles_shared,{}", self.styles_shared)?;
+        writeln!(f, "[PERF],styles_shared,{}", self.aggregated.styles_shared)?;
-        writeln!(f, "[PERF],styles_reused,{}", self.styles_reused)?;
+        writeln!(f, "[PERF],styles_reused,{}", self.aggregated.styles_reused)?;
         writeln!(f, "[PERF],selectors,{}", self.selectors)?;
         writeln!(f, "[PERF],revalidation_selectors,{}", self.revalidation_selectors)?;
         writeln!(f, "[PERF],dependency_selectors,{}", self.dependency_selectors)?;
@@ -382,29 +375,33 @@ impl fmt::Display for TraversalStatistics {
 }
 
 impl TraversalStatistics {
-    /// Computes the traversal time given the start time in seconds.
+    /// Generate complete traversal statistics.
-    pub fn finish<E, D>(&mut self, traversal: &D, parallel: bool, start: f64)
+    ///
+    /// The traversal time is computed given the start time in seconds.
+    pub fn new<E, D>(
+        aggregated: PerThreadTraversalStatistics,
+        traversal: &D,
+        parallel: bool,
+        start: f64
+    ) -> TraversalStatistics
     where
         E: TElement,
         D: DomTraversal<E>,
     {
         let threshold = traversal.shared_context().options.style_statistics_threshold;
         let stylist = traversal.shared_context().stylist;
-
+        let is_large = aggregated.elements_traversed as usize >= threshold;
-        self.is_parallel = Some(parallel);
+        TraversalStatistics {
-        self.is_large = Some(self.elements_traversed as usize >= threshold);
+            aggregated,
-        self.traversal_time_ms = (time::precise_time_s() - start) * 1000.0;
+            selectors: stylist.num_selectors() as u32,
-        self.selectors = stylist.num_selectors() as u32;
+            revalidation_selectors: stylist.num_revalidation_selectors() as u32,
-        self.revalidation_selectors = stylist.num_revalidation_selectors() as u32;
+            dependency_selectors: stylist.num_invalidations() as u32,
-        self.dependency_selectors = stylist.num_invalidations() as u32;
+            declarations: stylist.num_declarations() as u32,
-        self.declarations = stylist.num_declarations() as u32;
+            stylist_rebuilds: stylist.num_rebuilds() as u32,
-        self.stylist_rebuilds = stylist.num_rebuilds() as u32;
+            traversal_time_ms: (time::precise_time_s() - start) * 1000.0,
-    }
+            is_parallel: parallel,
-
+            is_large
-    /// Returns whether this traversal is 'large' in order to avoid console spam
+        }
-    /// from lots of tiny traversals.
-    pub fn is_large_traversal(&self) -> bool {
-        self.is_large.unwrap()
     }
 }
 
@@ -714,7 +711,7 @@ pub struct ThreadLocalStyleContext<E: TElement> {
     /// than the current element).
     pub selector_flags: SelectorFlagsMap<E>,
     /// Statistics about the traversal.
-    pub statistics: TraversalStatistics,
+    pub statistics: PerThreadTraversalStatistics,
     /// The struct used to compute and cache font metrics from style
     /// for evaluation of the font-relative em/ch units and font-size
     pub font_metrics_provider: E::FontMetricsProvider,
@@ -736,7 +733,7 @@ impl<E: TElement> ThreadLocalStyleContext<E> {
             new_animations_sender: shared.local_context_creation_data.lock().unwrap().new_animations_sender.clone(),
             tasks: SequentialTaskList(Vec::new()),
             selector_flags: SelectorFlagsMap::new(),
-            statistics: TraversalStatistics::default(),
+            statistics: PerThreadTraversalStatistics::default(),
             font_metrics_provider: E::FontMetricsProvider::create_from(shared),
             stack_limit_checker: StackLimitChecker::new(
                 (STYLE_THREAD_STACK_SIZE_KB - STACK_SAFETY_MARGIN_KB) * 1024),
@@ -753,7 +750,7 @@ impl<E: TElement> ThreadLocalStyleContext<E> {
             bloom_filter: StyleBloom::new(),
             tasks: SequentialTaskList(Vec::new()),
             selector_flags: SelectorFlagsMap::new(),
-            statistics: TraversalStatistics::default(),
+            statistics: PerThreadTraversalStatistics::default(),
             font_metrics_provider: E::FontMetricsProvider::create_from(shared),
             stack_limit_checker: StackLimitChecker::new(
                 (STYLE_THREAD_STACK_SIZE_KB - STACK_SAFETY_MARGIN_KB) * 1024),

components/style/driver.rs

@@ -7,7 +7,7 @@
 
 #![deny(missing_docs)]
 
-use context::{StyleContext, ThreadLocalStyleContext};
+use context::{StyleContext, ThreadLocalStyleContext, TraversalStatistics};
 use dom::{SendNode, TElement, TNode};
 use parallel;
 use parallel::{DispatchMode, WORK_UNIT_MAX};
@@ -128,9 +128,14 @@ where
             });
         }
 
-        aggregate.finish(traversal, parallel, start_time.unwrap());
+        let stats = TraversalStatistics::new(
-        if aggregate.is_large_traversal() {
+            aggregate,
-             println!("{}", aggregate);
+            traversal,
+            parallel,
+            start_time.unwrap()
+        );
+        if stats.is_large {
+             println!("{}", stats);
         }
     }
 }