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YJIT: increase context cache size to 1024 redux (#11140)

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* YJIT: increase context cache size to 1024 redux

* Move context hashing code outside of unsafe block

* Avoid allocating large table on the stack, which would cause a stack overflow

Co-authored by Alan Wu @XrXr
This commit is contained in:
Maxime Chevalier-Boisvert 2024-07-11 15:01:05 -04:00 committed by GitHub
parent 1f6aeadc82
commit 3fbf9df39a
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GPG Key ID: B5690EEEBB952194
1 changed files with 15 additions and 13 deletions
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28
yjit/src/core.rs
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@ -842,7 +842,7 @@ enum CtxOp {
}
// Number of entries in the context cache
const CTX_CACHE_SIZE: usize = 512;
const CTX_CACHE_SIZE: usize = 1024;
// Cache of the last contexts encoded
// Empirically this saves a few percent of memory
@ -906,18 +906,20 @@ impl Context {
// Store an entry in a cache of recently encoded/decoded contexts
fn cache_set(ctx: &Context, idx: u32)
{
// Compute the hash for this context
let mut hasher = DefaultHasher::new();
ctx.hash(&mut hasher);
let ctx_hash = hasher.finish() as usize;
unsafe {
// Lazily initialize the context cache
if CTX_CACHE == None {
let empty_tbl = [(Context::default(), 0); CTX_CACHE_SIZE];
CTX_CACHE = Some(Box::new(empty_tbl));
// Here we use the vec syntax to avoid allocating the large table on the stack,
// as this can cause a stack overflow
let tbl = vec![(Context::default(), 0); CTX_CACHE_SIZE].into_boxed_slice().try_into().unwrap();
CTX_CACHE = Some(tbl);
}
// Compute the hash for this context
let mut hasher = DefaultHasher::new();
ctx.hash(&mut hasher);
let ctx_hash = hasher.finish() as usize;
// Write a cache entry for this context
let cache = CTX_CACHE.as_mut().unwrap();
cache[ctx_hash % CTX_CACHE_SIZE] = (*ctx, idx);
@ -927,6 +929,11 @@ impl Context {
// Lookup the context in a cache of recently encoded/decoded contexts
fn cache_get(ctx: &Context) -> Option<u32>
{
// Compute the hash for this context
let mut hasher = DefaultHasher::new();
ctx.hash(&mut hasher);
let ctx_hash = hasher.finish() as usize;
unsafe {
if CTX_CACHE == None {
return None;
@ -934,11 +941,6 @@ impl Context {
let cache = CTX_CACHE.as_mut().unwrap();
// Compute the hash for this context
let mut hasher = DefaultHasher::new();
ctx.hash(&mut hasher);
let ctx_hash = hasher.finish() as usize;
// Check that the context for this cache entry mmatches
let cache_entry = &cache[ctx_hash % CTX_CACHE_SIZE];
if cache_entry.0 == *ctx {