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Use a u32 index for stream store (#451)

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A connection can never have more than u32::MAX >> 1 streams, so we'll
never store more than that many in the store slab. Define the
`SlabIndex` as a `u32` to reduce the number of bytes moved around.
This commit is contained in:
Sean McArthur
2020-02-28 15:30:48 -08:00
committed by GitHub
parent 78c8ec6968
commit 1b01300eeb
1 changed files with 8 additions and 6 deletions
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14
src/proto/streams/store.rs
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@@ -30,8 +30,10 @@ pub(crate) struct Key {
stream_id: StreamId, stream_id: StreamId,
} }
// We can never have more than `StreamId::MAX` streams in the store,
// so we can save a smaller index (u32 vs usize).
#[derive(Debug, Clone, Copy, PartialEq, Eq)] #[derive(Debug, Clone, Copy, PartialEq, Eq)]
struct SlabIndex(usize); struct SlabIndex(u32);
#[derive(Debug)] #[derive(Debug)]
pub(super) struct Queue<N> { pub(super) struct Queue<N> {
@@ -102,7 +104,7 @@ impl Store {
} }
pub fn insert(&mut self, id: StreamId, val: Stream) -> Ptr { pub fn insert(&mut self, id: StreamId, val: Stream) -> Ptr {
let index = SlabIndex(self.slab.insert(val)); let index = SlabIndex(self.slab.insert(val) as u32);
assert!(self.ids.insert(id, index).is_none()); assert!(self.ids.insert(id, index).is_none());
Ptr { Ptr {
@@ -171,7 +173,7 @@ impl ops::Index<Key> for Store {
fn index(&self, key: Key) -> &Self::Output { fn index(&self, key: Key) -> &Self::Output {
self.slab self.slab
.get(key.index.0) .get(key.index.0 as usize)
.filter(|s| s.id == key.stream_id) .filter(|s| s.id == key.stream_id)
.unwrap_or_else(|| { .unwrap_or_else(|| {
panic!("dangling store key for stream_id={:?}", key.stream_id); panic!("dangling store key for stream_id={:?}", key.stream_id);
@@ -182,7 +184,7 @@ impl ops::Index<Key> for Store {
impl ops::IndexMut<Key> for Store { impl ops::IndexMut<Key> for Store {
fn index_mut(&mut self, key: Key) -> &mut Self::Output { fn index_mut(&mut self, key: Key) -> &mut Self::Output {
self.slab self.slab
.get_mut(key.index.0) .get_mut(key.index.0 as usize)
.filter(|s| s.id == key.stream_id) .filter(|s| s.id == key.stream_id)
.unwrap_or_else(|| { .unwrap_or_else(|| {
panic!("dangling store key for stream_id={:?}", key.stream_id); panic!("dangling store key for stream_id={:?}", key.stream_id);
@@ -330,7 +332,7 @@ impl<'a> Ptr<'a> {
debug_assert!(!self.store.ids.contains_key(&self.key.stream_id)); debug_assert!(!self.store.ids.contains_key(&self.key.stream_id));
// Remove the stream state // Remove the stream state
let stream = self.store.slab.remove(self.key.index.0); let stream = self.store.slab.remove(self.key.index.0 as usize);
assert_eq!(stream.id, self.key.stream_id); assert_eq!(stream.id, self.key.stream_id);
stream.id stream.id
} }
@@ -390,7 +392,7 @@ impl<'a> VacantEntry<'a> {
pub fn insert(self, value: Stream) -> Key { pub fn insert(self, value: Stream) -> Key {
// Insert the value in the slab // Insert the value in the slab
let stream_id = value.id; let stream_id = value.id;
let index = SlabIndex(self.slab.insert(value)); let index = SlabIndex(self.slab.insert(value) as u32);
// Insert the handle in the ID map // Insert the handle in the ID map
self.ids.insert(index); self.ids.insert(index);