summaryrefslogtreecommitdiffstats
path: root/gfx/wr/webrender/src/intern.rs
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--gfx/wr/webrender/src/intern.rs469
1 files changed, 469 insertions, 0 deletions
diff --git a/gfx/wr/webrender/src/intern.rs b/gfx/wr/webrender/src/intern.rs
new file mode 100644
index 0000000000..d865a93eee
--- /dev/null
+++ b/gfx/wr/webrender/src/intern.rs
@@ -0,0 +1,469 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! The interning module provides a generic data structure
+//! interning container. It is similar in concept to a
+//! traditional string interning container, but it is
+//! specialized to the WR thread model.
+//!
+//! There is an Interner structure, that lives in the
+//! scene builder thread, and a DataStore structure
+//! that lives in the frame builder thread.
+//!
+//! Hashing, interning and handle creation is done by
+//! the interner structure during scene building.
+//!
+//! Delta changes for the interner are pushed during
+//! a transaction to the frame builder. The frame builder
+//! is then able to access the content of the interned
+//! handles quickly, via array indexing.
+//!
+//! Epoch tracking ensures that the garbage collection
+//! step which the interner uses to remove items is
+//! only invoked on items that the frame builder thread
+//! is no longer referencing.
+//!
+//! Items in the data store are stored in a traditional
+//! free-list structure, for content access and memory
+//! usage efficiency.
+//!
+//! The epoch is incremented each time a scene is
+//! built. The most recently used scene epoch is
+//! stored inside each handle. This is then used for
+//! cache invalidation.
+
+use crate::internal_types::FastHashMap;
+use malloc_size_of::MallocSizeOf;
+use std::fmt::Debug;
+use std::hash::Hash;
+use std::marker::PhantomData;
+use std::{ops, u64};
+use crate::util::VecHelper;
+use crate::profiler::TransactionProfile;
+
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+#[derive(Debug, Copy, Clone, Hash, MallocSizeOf, PartialEq, Eq)]
+struct Epoch(u32);
+
+/// A list of updates to be applied to the data store,
+/// provided by the interning structure.
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+#[derive(MallocSizeOf)]
+pub struct UpdateList<S> {
+ /// Items to insert.
+ pub insertions: Vec<Insertion<S>>,
+
+ /// Items to remove.
+ pub removals: Vec<Removal>,
+}
+
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+#[derive(MallocSizeOf)]
+pub struct Insertion<S> {
+ pub index: usize,
+ pub uid: ItemUid,
+ pub value: S,
+}
+
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+#[derive(MallocSizeOf)]
+pub struct Removal {
+ pub index: usize,
+ pub uid: ItemUid,
+}
+
+impl<S> UpdateList<S> {
+ fn new() -> UpdateList<S> {
+ UpdateList {
+ insertions: Vec::new(),
+ removals: Vec::new(),
+ }
+ }
+
+ fn take_and_preallocate(&mut self) -> UpdateList<S> {
+ UpdateList {
+ insertions: self.insertions.take_and_preallocate(),
+ removals: self.removals.take_and_preallocate(),
+ }
+ }
+}
+
+/// A globally, unique identifier
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+#[derive(Debug, Copy, Clone, Eq, Hash, MallocSizeOf, PartialEq)]
+pub struct ItemUid {
+ uid: u64,
+}
+
+impl ItemUid {
+ // Intended for debug usage only
+ pub fn get_uid(&self) -> u64 {
+ self.uid
+ }
+}
+
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+#[derive(Debug, Hash, MallocSizeOf, PartialEq, Eq)]
+pub struct Handle<I> {
+ index: u32,
+ epoch: Epoch,
+ _marker: PhantomData<I>,
+}
+
+impl<I> Clone for Handle<I> {
+ fn clone(&self) -> Self {
+ Handle {
+ index: self.index,
+ epoch: self.epoch,
+ _marker: self._marker,
+ }
+ }
+}
+
+impl<I> Copy for Handle<I> {}
+
+impl<I> Handle<I> {
+ pub fn uid(&self) -> ItemUid {
+ ItemUid {
+ // The index in the freelist + the epoch it was interned generates a stable
+ // unique id for an interned element.
+ uid: ((self.index as u64) << 32) | self.epoch.0 as u64
+ }
+ }
+
+ pub const INVALID: Self = Handle { index: !0, epoch: Epoch(!0), _marker: PhantomData };
+}
+
+pub trait InternDebug {
+ fn on_interned(&self, _uid: ItemUid) {}
+}
+
+/// The data store lives in the frame builder thread. It
+/// contains a free-list of items for fast access.
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+#[derive(MallocSizeOf)]
+pub struct DataStore<I: Internable> {
+ items: Vec<Option<I::StoreData>>,
+}
+
+impl<I: Internable> Default for DataStore<I> {
+ fn default() -> Self {
+ DataStore {
+ items: Vec::new(),
+ }
+ }
+}
+
+impl<I: Internable> DataStore<I> {
+ /// Apply any updates from the scene builder thread to
+ /// this data store.
+ pub fn apply_updates(
+ &mut self,
+ update_list: UpdateList<I::Key>,
+ profile: &mut TransactionProfile,
+ ) {
+ for insertion in update_list.insertions {
+ self.items
+ .entry(insertion.index)
+ .set(Some(insertion.value.into()));
+ }
+
+ for removal in update_list.removals {
+ self.items[removal.index] = None;
+ }
+
+ profile.set(I::PROFILE_COUNTER, self.items.len());
+ }
+}
+
+/// Retrieve an item from the store via handle
+impl<I: Internable> ops::Index<Handle<I>> for DataStore<I> {
+ type Output = I::StoreData;
+ fn index(&self, handle: Handle<I>) -> &I::StoreData {
+ self.items[handle.index as usize].as_ref().expect("Bad datastore lookup")
+ }
+}
+
+/// Retrieve a mutable item from the store via handle
+/// Retrieve an item from the store via handle
+impl<I: Internable> ops::IndexMut<Handle<I>> for DataStore<I> {
+ fn index_mut(&mut self, handle: Handle<I>) -> &mut I::StoreData {
+ self.items[handle.index as usize].as_mut().expect("Bad datastore lookup")
+ }
+}
+
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+#[derive(MallocSizeOf)]
+struct ItemDetails<I> {
+ /// Frame that this element was first interned
+ interned_epoch: Epoch,
+ /// Last frame this element was referenced (used to GC intern items)
+ last_used_epoch: Epoch,
+ /// Index into the freelist this item is located
+ index: usize,
+ /// Type marker for create_handle method
+ _marker: PhantomData<I>,
+}
+
+impl<I> ItemDetails<I> {
+ /// Construct a stable handle value from the item details
+ fn create_handle(&self) -> Handle<I> {
+ Handle {
+ index: self.index as u32,
+ epoch: self.interned_epoch,
+ _marker: PhantomData,
+ }
+ }
+}
+
+/// The main interning data structure. This lives in the
+/// scene builder thread, and handles hashing and interning
+/// unique data structures. It also manages a free-list for
+/// the items in the data store, which is synchronized via
+/// an update list of additions / removals.
+#[cfg_attr(feature = "capture", derive(Serialize))]
+#[cfg_attr(feature = "replay", derive(Deserialize))]
+#[derive(MallocSizeOf)]
+pub struct Interner<I: Internable> {
+ /// Uniquely map an interning key to a handle
+ map: FastHashMap<I::Key, ItemDetails<I>>,
+ /// List of free slots in the data store for re-use.
+ free_list: Vec<usize>,
+ /// Pending list of updates that need to be applied.
+ update_list: UpdateList<I::Key>,
+ /// The current epoch for the interner.
+ current_epoch: Epoch,
+ /// The information associated with each interned
+ /// item that can be accessed by the interner.
+ local_data: Vec<I::InternData>,
+}
+
+impl<I: Internable> Default for Interner<I> {
+ fn default() -> Self {
+ Interner {
+ map: FastHashMap::default(),
+ free_list: Vec::new(),
+ update_list: UpdateList::new(),
+ current_epoch: Epoch(1),
+ local_data: Vec::new(),
+ }
+ }
+}
+
+impl<I: Internable> Interner<I> {
+ /// Intern a data structure, and return a handle to
+ /// that data. The handle can then be stored in the
+ /// frame builder, and safely accessed via the data
+ /// store that lives in the frame builder thread.
+ /// The provided closure is invoked to build the
+ /// local data about an interned structure if the
+ /// key isn't already interned.
+ pub fn intern<F>(
+ &mut self,
+ data: &I::Key,
+ fun: F,
+ ) -> Handle<I> where F: FnOnce() -> I::InternData {
+ // Use get_mut rather than entry here to avoid
+ // cloning the (sometimes large) key in the common
+ // case, where the data already exists in the interner.
+ if let Some(details) = self.map.get_mut(data) {
+ // Update the last referenced frame for this element
+ details.last_used_epoch = self.current_epoch;
+ // Return a stable handle value for dependency checking
+ return details.create_handle();
+ }
+
+ // We need to intern a new data item. First, find out
+ // if there is a spare slot in the free-list that we
+ // can use. Otherwise, append to the end of the list.
+ let index = match self.free_list.pop() {
+ Some(index) => index,
+ None => self.local_data.len(),
+ };
+
+ // Generate a handle for access via the data store.
+ let handle = Handle {
+ index: index as u32,
+ epoch: self.current_epoch,
+ _marker: PhantomData,
+ };
+
+ let uid = handle.uid();
+
+ // Add a pending update to insert the new data.
+ self.update_list.insertions.push(Insertion {
+ index,
+ uid,
+ value: data.clone(),
+ });
+
+ #[cfg(debug_assertions)]
+ data.on_interned(uid);
+
+ // Store this handle so the next time it is
+ // interned, it gets re-used.
+ self.map.insert(data.clone(), ItemDetails {
+ interned_epoch: self.current_epoch,
+ last_used_epoch: self.current_epoch,
+ index,
+ _marker: PhantomData,
+ });
+
+ // Create the local data for this item that is
+ // being interned.
+ self.local_data.entry(index).set(fun());
+
+ handle
+ }
+
+ /// Retrieve the pending list of updates for an interner
+ /// that need to be applied to the data store. Also run
+ /// a GC step that removes old entries.
+ pub fn end_frame_and_get_pending_updates(&mut self) -> UpdateList<I::Key> {
+ let mut update_list = self.update_list.take_and_preallocate();
+
+ let free_list = &mut self.free_list;
+ let current_epoch = self.current_epoch.0;
+
+ // First, run a GC step. Walk through the handles, and
+ // if we find any that haven't been used for some time,
+ // remove them. If this ever shows up in profiles, we
+ // can make the GC step partial (scan only part of the
+ // map each frame). It also might make sense in the
+ // future to adjust how long items remain in the cache
+ // based on the current size of the list.
+ self.map.retain(|_, details| {
+ if details.last_used_epoch.0 + 10 < current_epoch {
+ // To expire an item:
+ // - Add index to the free-list for re-use.
+ // - Add an update to the data store to invalidate this slot.
+ // - Remove from the hash map.
+ free_list.push(details.index);
+ update_list.removals.push(Removal {
+ index: details.index,
+ uid: details.create_handle().uid(),
+ });
+ return false;
+ }
+
+ true
+ });
+
+ // Begin the next epoch
+ self.current_epoch = Epoch(self.current_epoch.0 + 1);
+
+ update_list
+ }
+}
+
+/// Retrieve the local data for an item from the interner via handle
+impl<I: Internable> ops::Index<Handle<I>> for Interner<I> {
+ type Output = I::InternData;
+ fn index(&self, handle: Handle<I>) -> &I::InternData {
+ &self.local_data[handle.index as usize]
+ }
+}
+
+/// Meta-macro to enumerate the various interner identifiers and types.
+///
+/// IMPORTANT: Keep this synchronized with the list in mozilla-central located at
+/// gfx/webrender_bindings/webrender_ffi.h
+///
+/// Note that this could be a lot less verbose if concat_idents! were stable. :-(
+#[macro_export]
+macro_rules! enumerate_interners {
+ ($macro_name: ident) => {
+ $macro_name! {
+ clip: ClipIntern,
+ prim: PrimitiveKeyKind,
+ normal_border: NormalBorderPrim,
+ image_border: ImageBorder,
+ image: Image,
+ yuv_image: YuvImage,
+ line_decoration: LineDecoration,
+ linear_grad: LinearGradient,
+ radial_grad: RadialGradient,
+ conic_grad: ConicGradient,
+ picture: Picture,
+ text_run: TextRun,
+ filter_data: FilterDataIntern,
+ backdrop_capture: BackdropCapture,
+ backdrop_render: BackdropRender,
+ polygon: PolygonIntern,
+ }
+ }
+}
+
+macro_rules! declare_interning_memory_report {
+ ( $( $name:ident: $ty:ident, )+ ) => {
+ ///
+ #[repr(C)]
+ #[derive(AddAssign, Clone, Debug, Default)]
+ pub struct InternerSubReport {
+ $(
+ ///
+ pub $name: usize,
+ )+
+ }
+ }
+}
+
+enumerate_interners!(declare_interning_memory_report);
+
+/// Memory report for interning-related data structures.
+/// cbindgen:derive-eq=false
+/// cbindgen:derive-ostream=false
+#[repr(C)]
+#[derive(Clone, Debug, Default)]
+pub struct InterningMemoryReport {
+ ///
+ pub interners: InternerSubReport,
+ ///
+ pub data_stores: InternerSubReport,
+}
+
+impl ::std::ops::AddAssign for InterningMemoryReport {
+ fn add_assign(&mut self, other: InterningMemoryReport) {
+ self.interners += other.interners;
+ self.data_stores += other.data_stores;
+ }
+}
+
+// The trick to make trait bounds configurable by features.
+mod dummy {
+ #[cfg(not(feature = "capture"))]
+ pub trait Serialize {}
+ #[cfg(not(feature = "capture"))]
+ impl<T> Serialize for T {}
+ #[cfg(not(feature = "replay"))]
+ pub trait Deserialize<'a> {}
+ #[cfg(not(feature = "replay"))]
+ impl<'a, T> Deserialize<'a> for T {}
+}
+#[cfg(feature = "capture")]
+use serde::Serialize as InternSerialize;
+#[cfg(not(feature = "capture"))]
+use self::dummy::Serialize as InternSerialize;
+#[cfg(feature = "replay")]
+use serde::Deserialize as InternDeserialize;
+#[cfg(not(feature = "replay"))]
+use self::dummy::Deserialize as InternDeserialize;
+
+/// Implement `Internable` for a type that wants to participate in interning.
+pub trait Internable: MallocSizeOf {
+ type Key: Eq + Hash + Clone + Debug + MallocSizeOf + InternDebug + InternSerialize + for<'a> InternDeserialize<'a>;
+ type StoreData: From<Self::Key> + MallocSizeOf + InternSerialize + for<'a> InternDeserialize<'a>;
+ type InternData: MallocSizeOf + InternSerialize + for<'a> InternDeserialize<'a>;
+
+ // Profile counter indices, see the list in profiler.rs
+ const PROFILE_COUNTER: usize;
+}