summaryrefslogtreecommitdiffstats
path: root/gfx/wr/webrender/src/intern.rs
blob: 2a0cde16d30fca8c4123e7fcae9bd130517f1b13 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
/* 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;
use peek_poke::PeekPoke;

#[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, PeekPoke, Default)]
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;
}