Rachelint commented on code in PR #6155:
URL: https://github.com/apache/arrow-rs/pull/6155#discussion_r1711713998
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arrow-buffer/src/buffer/null.rs:
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@@ -131,9 +176,20 @@ impl NullBuffer {
}
/// Returns the null count for this [`NullBuffer`]
- #[inline]
pub fn null_count(&self) -> usize {
- self.null_count
+ match &self.null_count {
+ NullCount::Eager(v) => *v,
+ NullCount::Lazy(v) => {
+ let cached_null_count = v.load(Ordering::Acquire);
+ if cached_null_count != UNINITIALIZED_NULL_COUNT {
+ return cached_null_count as usize;
+ }
+
+ let computed_null_count = self.buffer.len() -
self.buffer.count_set_bits();
+ v.store(computed_null_count as i64, Ordering::Release);
Review Comment:
> ( They would be similiar in x86, just affect reordering )?
It may hurt the cpu cache, too? But I know few about the detial.
I agree just let the compiler to decide if it should be inlined, and let
`lto = true` is a good choice if we actually care about it?
https://matklad.github.io/2021/07/09/inline-in-rust.html
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