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perf(linter): use NonZeroUsize for pending module cache entries (#6439)

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Using `NonZeroUsize` lets `rustc` detect a niche value, shrinking the size of `CacheStateEntry` from 16 bytes to 8. It has the added benefit of making `CacheStateEntry::PendingStore`'s purpose clearer.
This commit is contained in:
DonIsaac 2024-10-11 02:11:28 +00:00
parent 6a0a5337e1
commit c00f669435
1 changed files with 8 additions and 5 deletions
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13
crates/oxc_linter/src/service/module_cache.rs
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@ -6,6 +6,7 @@ use std::{
use dashmap::{mapref::one::Ref, DashMap};
use oxc_semantic::ModuleRecord;
use rustc_hash::FxHashMap;
use std::num::NonZeroUsize;
/// `CacheState` and `CacheStateEntry` are used to fix the problem where
/// there is a brief moment when a concurrent fetch can miss the cache.
@ -21,7 +22,7 @@ type CacheState = Mutex<FxHashMap<Box<Path>, Arc<(Mutex<CacheStateEntry>, Condva
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
enum CacheStateEntry {
ReadyToConstruct,
PendingStore(usize),
PendingStore(NonZeroUsize),
}
/// Keyed by canonicalized path
@ -66,8 +67,9 @@ impl ModuleCache {
let cache_hit = if self.modules.contains_key(path) {
true
} else {
let i = if let CacheStateEntry::PendingStore(i) = *state { i } else { 0 };
*state = CacheStateEntry::PendingStore(i + 1);
let i = if let CacheStateEntry::PendingStore(i) = *state { i.get() } else { 0 };
// SAFETY: 1 + any natural number is always non-zero.
*state = CacheStateEntry::PendingStore(unsafe { NonZeroUsize::new_unchecked(i + 1) });
false
};
@ -108,13 +110,14 @@ impl ModuleCache {
};
let mut state = lock.lock().expect("Failed lock inner cache state");
if let CacheStateEntry::PendingStore(i) = *state {
let new = i - 1;
let new = i.get() - 1;
if new == 0 {
*state = CacheStateEntry::ReadyToConstruct;
// Notify the next thread waiting in line, if there is any.
cvar.notify_one();
} else {
*state = CacheStateEntry::PendingStore(new);
// SAFETY: new is never 0 because the previous branch checks for it.
*state = CacheStateEntry::PendingStore(unsafe { NonZeroUsize::new_unchecked(new) });
}
}
}