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arena: speed up TypedArena::clear and improve common patterns #56378

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Merged
merged 2 commits into from
Dec 2, 2018
Merged

arena: speed up TypedArena::clear and improve common patterns #56378

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ca0806c
arena: speed up TypedArena::clear
ljedrz Nov 30, 2018
95f32f1
arena: improve common patterns
ljedrz Nov 30, 2018
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24 changes: 14 additions & 10 deletions src/libarena/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -224,14 +224,14 @@ impl<T> TypedArena<T> {
unsafe {
// Clear the last chunk, which is partially filled.
let mut chunks_borrow = self.chunks.borrow_mut();
if let Some(mut last_chunk) = chunks_borrow.pop() {
if let Some(mut last_chunk) = chunks_borrow.last_mut() {
self.clear_last_chunk(&mut last_chunk);
let len = chunks_borrow.len();
// If `T` is ZST, code below has no effect.
for mut chunk in chunks_borrow.drain(..) {
for mut chunk in chunks_borrow.drain(..len-1) {
let cap = chunk.storage.cap();
chunk.destroy(cap);
}
chunks_borrow.push(last_chunk);
}
}
}
Expand Down Expand Up @@ -310,13 +310,8 @@ impl Default for DroplessArena {
impl DroplessArena {
pub fn in_arena<T: ?Sized>(&self, ptr: *const T) -> bool {
let ptr = ptr as *const u8 as *mut u8;
for chunk in &*self.chunks.borrow() {
if chunk.start() <= ptr && ptr < chunk.end() {
return true;
}
}

false
self.chunks.borrow().iter().any(|chunk| chunk.start() <= ptr && ptr < chunk.end())
}

fn align(&self, align: usize) {
Expand Down Expand Up @@ -408,7 +403,7 @@ impl DroplessArena {
{
assert!(!mem::needs_drop::<T>());
assert!(mem::size_of::<T>() != 0);
assert!(slice.len() != 0);
assert!(!slice.is_empty());

let mem = self.alloc_raw(
slice.len() * mem::size_of::<T>(),
Expand Down Expand Up @@ -604,6 +599,15 @@ mod tests {
}
}

#[bench]
pub fn bench_typed_arena_clear(b: &mut Bencher) {
let mut arena = TypedArena::default();
b.iter(|| {
arena.alloc(Point { x: 1, y: 2, z: 3 });
arena.clear();
})
}

// Drop tests

struct DropCounter<'a> {
Expand Down