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/* 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
//! Overview of the GPU cache.
//!
//! The main goal of the GPU cache is to allow on-demand
//! allocation and construction of GPU resources for the
//! vertex shaders to consume.
//!
//! Every item that wants to be stored in the GPU cache
//! should create a GpuCacheHandle that is used to refer
//! to a cached GPU resource. Creating a handle is a
//! cheap operation, that does *not* allocate room in the
//! cache.
//!
//! On any frame when that data is required, the caller
//! must request that handle, via ```request```. If the
//! data is not in the cache, the user provided closure
//! will be invoked to build the data.
//!
//! After ```end_frame``` has occurred, callers can
//! use the ```get_address``` API to get the allocated
//! address in the GPU cache of a given resource slot
//! for this frame.
use api::{DebugFlags, DocumentId, PremultipliedColorF};
#[cfg(test)]
use api::IdNamespace;
use api::units::*;
use euclid::{HomogeneousVector, Box2D};
use crate::internal_types::{FastHashMap, FastHashSet, FrameStamp, FrameId};
use crate::profiler::{self, TransactionProfile};
use crate::prim_store::VECS_PER_SEGMENT;
use crate::renderer::MAX_VERTEX_TEXTURE_WIDTH;
use crate::util::VecHelper;
use std::{u16, u32};
use std::num::NonZeroU32;
use std::ops::Add;
use std::time::{Duration, Instant};
/// At the time of this writing, Firefox uses about 15 GPU cache rows on
/// startup, and then gradually works its way up to the mid-30s with normal
/// browsing.
pub const GPU_CACHE_INITIAL_HEIGHT: i32 = 20;
const NEW_ROWS_PER_RESIZE: i32 = 10;
/// The number of frames an entry can go unused before being evicted.
const FRAMES_BEFORE_EVICTION: u64 = 10;
/// The ratio of utilized blocks to total blocks for which we start the clock
/// on reclaiming memory.
const RECLAIM_THRESHOLD: f32 = 0.2;
/// The amount of time utilization must be below the above threshold before we
/// blow away the cache and rebuild it.
const RECLAIM_DELAY_S: u64 = 5;
#[derive(Debug, Copy, Clone, Eq, MallocSizeOf, PartialEq)]
#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
struct Epoch(u32);
impl Epoch {
fn next(&mut self) {
*self = Epoch(self.0.wrapping_add(1));
}
}
#[derive(Debug, Copy, Clone, MallocSizeOf)]
#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
struct CacheLocation {
block_index: BlockIndex,
epoch: Epoch,
}
/// A single texel in RGBAF32 texture - 16 bytes.
#[derive(Copy, Clone, Debug, MallocSizeOf)]
#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
pub struct GpuBlockData {
data: [f32; 4],
}
impl GpuBlockData {
pub const EMPTY: Self = GpuBlockData { data: [0.0; 4] };
}
/// Conversion helpers for GpuBlockData
impl From<PremultipliedColorF> for GpuBlockData {
fn from(c: PremultipliedColorF) -> Self {
GpuBlockData {
data: [c.r, c.g, c.b, c.a],
}
}
}
impl From<[f32; 4]> for GpuBlockData {
fn from(data: [f32; 4]) -> Self {
GpuBlockData { data }
}
}
impl<P> From<Box2D<f32, P>> for GpuBlockData {
fn from(r: Box2D<f32, P>) -> Self {
GpuBlockData {
data: [
r.min.x,
r.min.y,
r.max.x,
r.max.y,
],
}
}
}
impl<P> From<HomogeneousVector<f32, P>> for GpuBlockData {
fn from(v: HomogeneousVector<f32, P>) -> Self {
GpuBlockData {
data: [
v.x,
v.y,
v.z,
v.w,
],
}
}
}
impl From<TexelRect> for GpuBlockData {
fn from(tr: TexelRect) -> Self {
GpuBlockData {
data: [tr.uv0.x, tr.uv0.y, tr.uv1.x, tr.uv1.y],
}
}
}
// A handle to a GPU resource.
#[derive(Debug, Copy, Clone, MallocSizeOf)]
#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
pub struct GpuCacheHandle {
location: Option<CacheLocation>,
}
impl GpuCacheHandle {
pub fn new() -> Self {
GpuCacheHandle { location: None }
}
pub fn as_int(self, gpu_cache: &GpuCache) -> i32 {
gpu_cache.get_address(&self).as_int()
}
}
// A unique address in the GPU cache. These are uploaded
// as part of the primitive instances, to allow the vertex
// shader to fetch the specific data.
#[repr(C)]
#[derive(Copy, Debug, Clone, MallocSizeOf, Eq, PartialEq)]
#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
pub struct GpuCacheAddress {
pub u: u16,
pub v: u16,
}
impl GpuCacheAddress {
fn new(u: usize, v: usize) -> Self {
GpuCacheAddress {
u: u as u16,
v: v as u16,
}
}
pub const INVALID: GpuCacheAddress = GpuCacheAddress {
u: u16::MAX,
v: u16::MAX,
};
pub fn as_int(self) -> i32 {
// TODO(gw): Temporarily encode GPU Cache addresses as a single int.
// In the future, we can change the PrimitiveInstanceData struct
// to use 2x u16 for the vertex attribute instead of an i32.
self.v as i32 * MAX_VERTEX_TEXTURE_WIDTH as i32 + self.u as i32
}
}
impl Add<usize> for GpuCacheAddress {
type Output = GpuCacheAddress;
fn add(self, other: usize) -> GpuCacheAddress {
GpuCacheAddress {
u: self.u + other as u16,
v: self.v,
}
}
}
// An entry in a free-list of blocks in the GPU cache.
#[derive(Debug, MallocSizeOf)]
#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
struct Block {
// The location in the cache of this block.
address: GpuCacheAddress,
// The current epoch (generation) of this block.
epoch: Epoch,
// Index of the next free block in the list it
// belongs to (either a free-list or the
// occupied list).
next: Option<BlockIndex>,
// The last frame this block was referenced.
last_access_time: FrameId,
}
impl Block {
fn new(
address: GpuCacheAddress,
next: Option<BlockIndex>,
frame_id: FrameId,
epoch: Epoch,
) -> Self {
Block {
address,
next,
last_access_time: frame_id,
epoch,
}
}
fn advance_epoch(&mut self, max_epoch: &mut Epoch) {
self.epoch.next();
if max_epoch.0 < self.epoch.0 {
max_epoch.0 = self.epoch.0;
}
}
/// Creates an invalid dummy block ID.
pub const INVALID: Block = Block {
address: GpuCacheAddress { u: 0, v: 0 },
epoch: Epoch(0),
next: None,
last_access_time: FrameId::INVALID,
};
}
/// Represents the index of a Block in the block array. We only create such
/// structs for blocks that represent the start of a chunk.
///
/// Because we use Option<BlockIndex> in a lot of places, we use a NonZeroU32
/// here and avoid ever using the index zero.
#[derive(Debug, Copy, Clone, MallocSizeOf)]
#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
struct BlockIndex(NonZeroU32);
impl BlockIndex {
fn new(idx: usize) -> Self {
debug_assert!(idx <= u32::MAX as usize);
BlockIndex(NonZeroU32::new(idx as u32).expect("Index zero forbidden"))
}
fn get(&self) -> usize {
self.0.get() as usize
}
}
// A row in the cache texture.
#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
#[derive(MallocSizeOf)]
struct Row {
// The fixed size of blocks that this row supports.
// Each row becomes a slab allocator for a fixed block size.
// This means no dealing with fragmentation within a cache
// row as items are allocated and freed.
block_count_per_item: usize,
}
impl Row {
fn new(block_count_per_item: usize) -> Self {
Row {
block_count_per_item,
}
}
}
// A list of update operations that can be applied on the cache
// this frame. The list of updates is created by the render backend
// during frame construction. It's passed to the render thread
// where GL commands can be applied.
#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
#[derive(MallocSizeOf)]
pub enum GpuCacheUpdate {
Copy {
block_index: usize,
block_count: usize,
address: GpuCacheAddress,
},
}
/// Command to inform the debug display in the renderer when chunks are allocated
/// or freed.
#[derive(MallocSizeOf)]
pub enum GpuCacheDebugCmd {
/// Describes an allocated chunk.
Alloc(GpuCacheDebugChunk),
/// Describes a freed chunk.
Free(GpuCacheAddress),
}
#[derive(Clone, MallocSizeOf)]
pub struct GpuCacheDebugChunk {
pub address: GpuCacheAddress,
pub size: usize,
}
#[must_use]
#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
#[derive(MallocSizeOf)]
pub struct GpuCacheUpdateList {
/// The frame current update list was generated from.
pub frame_id: FrameId,
/// Whether the texture should be cleared before updates
/// are applied.
pub clear: bool,
/// The current height of the texture. The render thread
/// should resize the texture if required.
pub height: i32,
/// List of updates to apply.
pub updates: Vec<GpuCacheUpdate>,
/// A flat list of GPU blocks that are pending upload
/// to GPU memory.
pub blocks: Vec<GpuBlockData>,
/// Whole state GPU block metadata for debugging.
#[cfg_attr(feature = "serde", serde(skip))]
pub debug_commands: Vec<GpuCacheDebugCmd>,
}
// Holds the free lists of fixed size blocks. Mostly
// just serves to work around the borrow checker.
#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
#[derive(MallocSizeOf)]
struct FreeBlockLists {
free_list_1: Option<BlockIndex>,
free_list_2: Option<BlockIndex>,
free_list_4: Option<BlockIndex>,
free_list_8: Option<BlockIndex>,
free_list_16: Option<BlockIndex>,
free_list_32: Option<BlockIndex>,
free_list_64: Option<BlockIndex>,
free_list_128: Option<BlockIndex>,
free_list_256: Option<BlockIndex>,
free_list_341: Option<BlockIndex>,
free_list_512: Option<BlockIndex>,
free_list_1024: Option<BlockIndex>,
}
impl FreeBlockLists {
fn new() -> Self {
FreeBlockLists {
free_list_1: None,
free_list_2: None,
free_list_4: None,
free_list_8: None,
free_list_16: None,
free_list_32: None,
free_list_64: None,
free_list_128: None,
free_list_256: None,
free_list_341: None,
free_list_512: None,
free_list_1024: None,
}
}
fn get_actual_block_count_and_free_list(
&mut self,
block_count: usize,
) -> (usize, &mut Option<BlockIndex>) {
// Find the appropriate free list to use based on the block size.
//
// Note that we cheat a bit with the 341 bucket, since it's not quite
// a divisor of 1024, because purecss-francine allocates many 260-block
// chunks, and there's no reason we shouldn't pack these three to a row.
// This means the allocation statistics will under-report by one block
// for each row using 341-block buckets, which is fine.
debug_assert_eq!(MAX_VERTEX_TEXTURE_WIDTH, 1024, "Need to update bucketing");
match block_count {
0 => panic!("Can't allocate zero sized blocks!"),
1 => (1, &mut self.free_list_1),
2 => (2, &mut self.free_list_2),
3..=4 => (4, &mut self.free_list_4),
5..=8 => (8, &mut self.free_list_8),
9..=16 => (16, &mut self.free_list_16),
17..=32 => (32, &mut self.free_list_32),
33..=64 => (64, &mut self.free_list_64),
65..=128 => (128, &mut self.free_list_128),
129..=256 => (256, &mut self.free_list_256),
257..=341 => (341, &mut self.free_list_341),
342..=512 => (512, &mut self.free_list_512),
513..=1024 => (1024, &mut self.free_list_1024),
_ => panic!("Can't allocate > MAX_VERTEX_TEXTURE_WIDTH per resource!"),
}
}
}
// CPU-side representation of the GPU resource cache texture.
#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
#[derive(MallocSizeOf)]
struct Texture {
// Current texture height
height: i32,
// All blocks that have been created for this texture
blocks: Vec<Block>,
// Metadata about each allocated row.
rows: Vec<Row>,
// The base Epoch for this texture.
base_epoch: Epoch,
// The maximum epoch reached. We track this along with the above so
// that we can rebuild the Texture and avoid collisions with handles
// allocated for the old texture.
max_epoch: Epoch,
// Free lists of available blocks for each supported
// block size in the texture. These are intrusive
// linked lists.
free_lists: FreeBlockLists,
// Linked list of currently occupied blocks. This
// makes it faster to iterate blocks looking for
// candidates to be evicted from the cache.
occupied_list_heads: FastHashMap<DocumentId, BlockIndex>,
// Pending blocks that have been written this frame
// and will need to be sent to the GPU.
pending_blocks: Vec<GpuBlockData>,
// Pending update commands.
updates: Vec<GpuCacheUpdate>,
// Profile stats
allocated_block_count: usize,
// The stamp at which we first reached our threshold for reclaiming `GpuCache`
// memory, or `None` if the threshold hasn't been reached.
#[cfg_attr(feature = "serde", serde(skip))]
reached_reclaim_threshold: Option<Instant>,
// List of debug commands to be sent to the renderer when the GPU cache
// debug display is enabled.
#[cfg_attr(feature = "serde", serde(skip))]
debug_commands: Vec<GpuCacheDebugCmd>,
// The current debug flags for the system.
debug_flags: DebugFlags,
}
impl Texture {
fn new(base_epoch: Epoch, debug_flags: DebugFlags) -> Self {
// Pre-fill the block array with one invalid block so that we never use
// 0 for a BlockIndex. This lets us use NonZeroU32 for BlockIndex, which
// saves memory.
let blocks = vec![Block::INVALID];
Texture {
height: GPU_CACHE_INITIAL_HEIGHT,
blocks,
rows: Vec::new(),
base_epoch,
max_epoch: base_epoch,
free_lists: FreeBlockLists::new(),
pending_blocks: Vec::new(),
updates: Vec::new(),
occupied_list_heads: FastHashMap::default(),
allocated_block_count: 0,
reached_reclaim_threshold: None,
debug_commands: Vec::new(),
debug_flags,
}
}
// Push new data into the cache. The ```pending_block_index``` field represents
// where the data was pushed into the texture ```pending_blocks``` array.
// Return the allocated address for this data.
fn push_data(
&mut self,
pending_block_index: Option<usize>,
block_count: usize,
frame_stamp: FrameStamp
) -> CacheLocation {
debug_assert!(frame_stamp.is_valid());
// Find the appropriate free list to use based on the block size.
let (alloc_size, free_list) = self.free_lists
.get_actual_block_count_and_free_list(block_count);
// See if we need a new row (if free-list has nothing available)
if free_list.is_none() {
if self.rows.len() as i32 == self.height {
self.height += NEW_ROWS_PER_RESIZE;
}
// Create a new row.
let items_per_row = MAX_VERTEX_TEXTURE_WIDTH / alloc_size;
let row_index = self.rows.len();
self.rows.push(Row::new(alloc_size));
// Create a ```Block``` for each possible allocation address
// in this row, and link it in to the free-list for this
// block size.
let mut prev_block_index = None;
for i in 0 .. items_per_row {
let address = GpuCacheAddress::new(i * alloc_size, row_index);
let block_index = BlockIndex::new(self.blocks.len());
let block = Block::new(address, prev_block_index, frame_stamp.frame_id(), self.base_epoch);
self.blocks.push(block);
prev_block_index = Some(block_index);
}
*free_list = prev_block_index;
}
// Given the code above, it's now guaranteed that there is a block
// available in the appropriate free-list. Pull a block from the
// head of the list.
let free_block_index = free_list.take().unwrap();
let block = &mut self.blocks[free_block_index.get()];
*free_list = block.next;
// Add the block to the occupied linked list.
block.next = self.occupied_list_heads.get(&frame_stamp.document_id()).cloned();
block.last_access_time = frame_stamp.frame_id();
self.occupied_list_heads.insert(frame_stamp.document_id(), free_block_index);
self.allocated_block_count += alloc_size;
if let Some(pending_block_index) = pending_block_index {
// Add this update to the pending list of blocks that need
// to be updated on the GPU.
self.updates.push(GpuCacheUpdate::Copy {
block_index: pending_block_index,
block_count,
address: block.address,
});
}
// If we're using the debug display, communicate the allocation to the
// renderer thread. Note that we do this regardless of whether or not
// pending_block_index is None (if it is, the renderer thread will fill
// in the data via a deferred resolve, but the block is still considered
// allocated).
if self.debug_flags.contains(DebugFlags::GPU_CACHE_DBG) {
self.debug_commands.push(GpuCacheDebugCmd::Alloc(GpuCacheDebugChunk {
address: block.address,
size: block_count,
}));
}
CacheLocation {
block_index: free_block_index,
epoch: block.epoch,
}
}
// Run through the list of occupied cache blocks and evict
// any old blocks that haven't been referenced for a while.
fn evict_old_blocks(&mut self, frame_stamp: FrameStamp) {
debug_assert!(frame_stamp.is_valid());
// Prune any old items from the list to make room.
// Traverse the occupied linked list and see
// which items have not been used for a long time.
let mut current_block = self.occupied_list_heads.get(&frame_stamp.document_id()).map(|x| *x);
let mut prev_block: Option<BlockIndex> = None;
while let Some(index) = current_block {
let (next_block, should_unlink) = {
let block = &mut self.blocks[index.get()];
let next_block = block.next;
let mut should_unlink = false;
// If this resource has not been used in the last
// few frames, free it from the texture and mark
// as empty.
if block.last_access_time + FRAMES_BEFORE_EVICTION < frame_stamp.frame_id() {
should_unlink = true;
// Get the row metadata from the address.
let row = &mut self.rows[block.address.v as usize];
// Use the row metadata to determine which free-list
// this block belongs to.
let (_, free_list) = self.free_lists
.get_actual_block_count_and_free_list(row.block_count_per_item);
block.advance_epoch(&mut self.max_epoch);
block.next = *free_list;
*free_list = Some(index);
self.allocated_block_count -= row.block_count_per_item;
if self.debug_flags.contains(DebugFlags::GPU_CACHE_DBG) {
let cmd = GpuCacheDebugCmd::Free(block.address);
self.debug_commands.push(cmd);
}
};
(next_block, should_unlink)
};
// If the block was released, we will need to remove it
// from the occupied linked list.
if should_unlink {
match prev_block {
Some(prev_block) => {
self.blocks[prev_block.get()].next = next_block;
}
None => {
match next_block {
Some(next_block) => {
self.occupied_list_heads.insert(frame_stamp.document_id(), next_block);
}
None => {
self.occupied_list_heads.remove(&frame_stamp.document_id());
}
}
}
}
} else {
prev_block = current_block;
}
current_block = next_block;
}
}
/// Returns the ratio of utilized blocks.
fn utilization(&self) -> f32 {
let total_blocks = self.rows.len() * MAX_VERTEX_TEXTURE_WIDTH;
debug_assert!(total_blocks > 0);
let ratio = self.allocated_block_count as f32 / total_blocks as f32;
debug_assert!(0.0 <= ratio && ratio <= 1.0, "Bad ratio: {}", ratio);
ratio
}
}
/// A wrapper object for GPU data requests,
/// works as a container that can only grow.
#[must_use]
pub struct GpuDataRequest<'a> {
//TODO: remove this, see
#[allow(dead_code)]
handle: &'a mut GpuCacheHandle,
frame_stamp: FrameStamp,
start_index: usize,
max_block_count: usize,
texture: &'a mut Texture,
}
impl<'a> GpuDataRequest<'a> {
pub fn push<B>(&mut self, block: B)
where
B: Into<GpuBlockData>,
{
self.texture.pending_blocks.push(block.into());
}
// Write the GPU cache data for an individual segment.
pub fn write_segment(
&mut self,
local_rect: LayoutRect,
extra_data: [f32; 4],
) {
let _ = VECS_PER_SEGMENT;
self.push(local_rect);
self.push(extra_data);
}
pub fn current_used_block_num(&self) -> usize {
self.texture.pending_blocks.len() - self.start_index
}
}
impl<'a> Drop for GpuDataRequest<'a> {
fn drop(&mut self) {
// Push the data to the texture pending updates list.
let block_count = self.current_used_block_num();
debug_assert!(block_count <= self.max_block_count);
let location = self.texture
.push_data(Some(self.start_index), block_count, self.frame_stamp);
self.handle.location = Some(location);
}
}
/// The main LRU cache interface.
#[cfg_attr(feature = "capture", derive(Serialize))]
#[cfg_attr(feature = "replay", derive(Deserialize))]
#[derive(MallocSizeOf)]
pub struct GpuCache {
/// Current FrameId.
now: FrameStamp,
/// CPU-side texture allocator.
texture: Texture,
/// Number of blocks requested this frame that don't
/// need to be re-uploaded.
saved_block_count: usize,
/// The current debug flags for the system.
debug_flags: DebugFlags,
/// Whether there is a pending clear to send with the
/// next update.
pending_clear: bool,
/// Indicates that prepare_for_frames has been called for this group of frames.
/// Used for sanity checks.
prepared_for_frames: bool,
/// This indicates that we performed a cleanup operation which requires all
/// documents to build a frame.
requires_frame_build: bool,
/// The set of documents which have had frames built in this update. Used for
/// sanity checks.
document_frames_to_build: FastHashSet<DocumentId>,
}
impl GpuCache {
pub fn new() -> Self {
let debug_flags = DebugFlags::empty();
GpuCache {
now: FrameStamp::INVALID,
texture: Texture::new(Epoch(0), debug_flags),
saved_block_count: 0,
debug_flags,
pending_clear: false,
prepared_for_frames: false,
requires_frame_build: false,
document_frames_to_build: FastHashSet::default(),
}
}
/// Creates a GpuCache and sets it up with a valid `FrameStamp`, which
/// is useful for avoiding panics when instantiating the `GpuCache`
/// directly from unit test code.
#[cfg(test)]
pub fn new_for_testing() -> Self {
let mut cache = Self::new();
let mut now = FrameStamp::first(DocumentId::new(IdNamespace(1), 1));
now.advance();
cache.prepared_for_frames = true;
cache.begin_frame(now);
cache
}
/// Drops everything in the GPU cache. Must not be called once gpu cache entries
/// for the next frame have already been requested.
pub fn clear(&mut self) {
assert!(self.texture.updates.is_empty(), "Clearing with pending updates");
let mut next_base_epoch = self.texture.max_epoch;
next_base_epoch.next();
self.texture = Texture::new(next_base_epoch, self.debug_flags);
self.saved_block_count = 0;
self.pending_clear = true;
self.requires_frame_build = true;
}
pub fn requires_frame_build(&self) -> bool {
self.requires_frame_build
}
pub fn prepare_for_frames(&mut self) {
self.prepared_for_frames = true;
if self.should_reclaim_memory() {
self.clear();
debug_assert!(self.document_frames_to_build.is_empty());
for &document_id in self.texture.occupied_list_heads.keys() {
self.document_frames_to_build.insert(document_id);
}
}
}
pub fn bookkeep_after_frames(&mut self) {
assert!(self.document_frames_to_build.is_empty());
assert!(self.prepared_for_frames);
self.requires_frame_build = false;
self.prepared_for_frames = false;
}
/// Begin a new frame.
pub fn begin_frame(&mut self, stamp: FrameStamp) {
debug_assert!(self.texture.pending_blocks.is_empty());
assert!(self.prepared_for_frames);
profile_scope!("begin_frame");
self.now = stamp;
self.texture.evict_old_blocks(self.now);
self.saved_block_count = 0;
}
// Invalidate a (possibly) existing block in the cache.
// This means the next call to request() for this location
// will rebuild the data and upload it to the GPU.
pub fn invalidate(&mut self, handle: &GpuCacheHandle) {
if let Some(ref location) = handle.location {
// don't invalidate blocks that are already re-assigned
if let Some(block) = self.texture.blocks.get_mut(location.block_index.get()) {
if block.epoch == location.epoch {
block.advance_epoch(&mut self.texture.max_epoch);
}
}
}
}
/// Request a resource be added to the cache. If the resource
/// is already in the cache, `None` will be returned.
pub fn request<'a>(&'a mut self, handle: &'a mut GpuCacheHandle) -> Option<GpuDataRequest<'a>> {
let mut max_block_count = MAX_VERTEX_TEXTURE_WIDTH;
// Check if the allocation for this handle is still valid.
if let Some(ref location) = handle.location {
if let Some(block) = self.texture.blocks.get_mut(location.block_index.get()) {
if block.epoch == location.epoch {
max_block_count = self.texture.rows[block.address.v as usize].block_count_per_item;
if block.last_access_time != self.now.frame_id() {
// Mark last access time to avoid evicting this block.
block.last_access_time = self.now.frame_id();
self.saved_block_count += max_block_count;
}
return None;
}
}
}
debug_assert!(self.now.is_valid());
Some(GpuDataRequest {
handle,
frame_stamp: self.now,
start_index: self.texture.pending_blocks.len(),
texture: &mut self.texture,
max_block_count,
})
}
// Push an array of data blocks to be uploaded to the GPU
// unconditionally for this frame. The cache handle will
// assert if the caller tries to retrieve the address
// of this handle on a subsequent frame. This is typically
// used for uploading data that changes every frame, and
// therefore makes no sense to try and cache.
pub fn push_per_frame_blocks(&mut self, blocks: &[GpuBlockData]) -> GpuCacheHandle {
let start_index = self.texture.pending_blocks.len();
self.texture.pending_blocks.extend_from_slice(blocks);
let location = self.texture
.push_data(Some(start_index), blocks.len(), self.now);
GpuCacheHandle {
location: Some(location),
}
}
// Reserve space in the cache for per-frame blocks that
// will be resolved by the render thread via the
// external image callback.
pub fn push_deferred_per_frame_blocks(&mut self, block_count: usize) -> GpuCacheHandle {
let location = self.texture.push_data(None, block_count, self.now);
GpuCacheHandle {
location: Some(location),
}
}
/// End the frame. Return the list of updates to apply to the
/// device specific cache texture.
pub fn end_frame(
&mut self,
profile: &mut TransactionProfile,
) -> FrameStamp {
profile_scope!("end_frame");
profile.set(profiler::GPU_CACHE_ROWS_TOTAL, self.texture.rows.len());
profile.set(profiler::GPU_CACHE_BLOCKS_TOTAL, self.texture.allocated_block_count);
profile.set(profiler::GPU_CACHE_BLOCKS_SAVED, self.saved_block_count);
let reached_threshold =
self.texture.rows.len() > (GPU_CACHE_INITIAL_HEIGHT as usize) &&
self.texture.utilization() < RECLAIM_THRESHOLD;
if reached_threshold {
self.texture.reached_reclaim_threshold.get_or_insert_with(Instant::now);
} else {
self.texture.reached_reclaim_threshold = None;
}
self.document_frames_to_build.remove(&self.now.document_id());
self.now
}
/// Returns true if utilization has been low enough for long enough that we
/// should blow the cache away and rebuild it.
pub fn should_reclaim_memory(&self) -> bool {
self.texture.reached_reclaim_threshold
.map_or(false, |t| t.elapsed() > Duration::from_secs(RECLAIM_DELAY_S))
}
/// Extract the pending updates from the cache.
pub fn extract_updates(&mut self) -> GpuCacheUpdateList {
let clear = self.pending_clear;
self.pending_clear = false;
GpuCacheUpdateList {
frame_id: self.now.frame_id(),
clear,
height: self.texture.height,
debug_commands: self.texture.debug_commands.take_and_preallocate(),
updates: self.texture.updates.take_and_preallocate(),
blocks: self.texture.pending_blocks.take_and_preallocate(),
}
}
/// Sets the current debug flags for the system.
pub fn set_debug_flags(&mut self, flags: DebugFlags) {
self.debug_flags = flags;
self.texture.debug_flags = flags;
}
/// Get the actual GPU address in the texture for a given slot ID.
/// It's assumed at this point that the given slot has been requested
/// and built for this frame. Attempting to get the address for a
/// freed or pending slot will panic!
pub fn get_address(&self, id: &GpuCacheHandle) -> GpuCacheAddress {
let location = id.location.expect("handle not requested or allocated!");
let block = &self.texture.blocks[location.block_index.get()];
debug_assert_eq!(block.epoch, location.epoch);
debug_assert_eq!(block.last_access_time, self.now.frame_id());
block.address
}
}
#[test]
#[cfg(target_pointer_width = "64")]
fn test_struct_sizes() {
use std::mem;
// We can end up with a lot of blocks stored in the global vec, and keeping
// them small helps reduce memory overhead.
assert_eq!(mem::size_of::<Block>(), 24, "Block size changed");
}