improve performance of recursion guard #1156
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,4 +1,5 @@ | ||
| use ahash::AHashSet; | ||
| use std::hash::Hash; | ||
|
|
||
| type RecursionKey = ( | ||
| // Identifier for the input object, e.g. the id() of a Python dict | ||
|
|
@@ -13,56 +14,130 @@ type RecursionKey = ( | |
| /// It's used in `validators/definition` to detect when a reference is reused within itself. | ||
| #[derive(Debug, Clone, Default)] | ||
| pub struct RecursionGuard { | ||
| ids: SmallContainer<RecursionKey>, | ||
| // depth could be a hashmap {validator_id => depth} but for simplicity and performance it's easier to just | ||
| // use one number for all validators | ||
| depth: u8, | ||
| } | ||
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| // A hard limit to avoid stack overflows when rampant recursion occurs | ||
| pub const RECURSION_GUARD_LIMIT: u8 = if cfg!(any(target_family = "wasm", all(windows, PyPy))) { | ||
| // wasm and windows PyPy have very limited stack sizes | ||
| 49 | ||
| } else if cfg!(any(PyPy, windows)) { | ||
| // PyPy and Windows in general have more restricted stack space | ||
| 99 | ||
| } else { | ||
| 255 | ||
| }; | ||
|
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| impl RecursionGuard { | ||
| // insert a new value | ||
| // * return `None` if the array/set already had it in it | ||
| // * return `Some(index)` if the array didn't have it in it and it was inserted | ||
| pub fn contains_or_insert(&mut self, obj_id: usize, node_id: usize) -> Option<usize> { | ||
| self.ids.contains_or_insert((obj_id, node_id)) | ||
| } | ||
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| // see #143 this is used as a backup in case the identity check recursion guard fails | ||
| #[must_use] | ||
| #[cfg(any(target_family = "wasm", windows, PyPy))] | ||
| pub fn incr_depth(&mut self) -> bool { | ||
| // use saturating_add as it's faster (since there's no error path) | ||
| // and the RECURSION_GUARD_LIMIT check will be hit before it overflows | ||
| debug_assert!(RECURSION_GUARD_LIMIT < 255); | ||
| self.depth = self.depth.saturating_add(1); | ||
| self.depth > RECURSION_GUARD_LIMIT | ||
| } | ||
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| #[must_use] | ||
| #[cfg(not(any(target_family = "wasm", windows, PyPy)))] | ||
| pub fn incr_depth(&mut self) -> bool { | ||
| debug_assert_eq!(RECURSION_GUARD_LIMIT, 255); | ||
| // use checked_add to check if we've hit the limit | ||
| if let Some(depth) = self.depth.checked_add(1) { | ||
| self.depth = depth; | ||
| false | ||
| } else { | ||
| true | ||
| } | ||
| } | ||
|
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||
| pub fn decr_depth(&mut self) { | ||
| // for the same reason as incr_depth, use saturating_sub | ||
| self.depth = self.depth.saturating_sub(1); | ||
| } | ||
|
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||
| pub fn remove(&mut self, obj_id: usize, node_id: usize, index: usize) { | ||
| self.ids.remove(&(obj_id, node_id), index); | ||
| } | ||
| } | ||
|
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| // trial and error suggests this is a good value, going higher causes array lookups to get significantly slower | ||
| const ARRAY_SIZE: usize = 16; | ||
|
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| #[derive(Debug, Clone)] | ||
| enum SmallContainer<T> { | ||
| Array([Option<T>; ARRAY_SIZE]), | ||
| Set(AHashSet<T>), | ||
| } | ||
|
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| impl<T: Copy> Default for SmallContainer<T> { | ||
| fn default() -> Self { | ||
| Self::Array([None; ARRAY_SIZE]) | ||
| } | ||
| } | ||
|
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| impl<T: Eq + Hash + Clone> SmallContainer<T> { | ||
| // insert a new value | ||
| // * return `None` if the array/set already had it in it | ||
| // * return `Some(index)` if the array didn't have it in it and it was inserted | ||
| pub fn contains_or_insert(&mut self, v: T) -> Option<usize> { | ||
| match self { | ||
| Self::Array(array) => { | ||
| for (index, op_value) in array.iter_mut().enumerate() { | ||
| if let Some(existing) = op_value { | ||
| if existing == &v { | ||
| return None; | ||
| } | ||
| } else { | ||
| *op_value = Some(v); | ||
|
||
| return Some(index); | ||
| } | ||
| } | ||
|
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| // No array slots exist; convert to set | ||
| let mut set: AHashSet<T> = AHashSet::with_capacity(ARRAY_SIZE + 1); | ||
| for existing in array.iter_mut() { | ||
| set.insert(existing.take().unwrap()); | ||
| } | ||
| set.insert(v); | ||
| *self = Self::Set(set); | ||
| // id doesn't matter here as we'll be removing from a set | ||
| Some(0) | ||
| } | ||
| // https://doc.rust-lang.org/std/collections/struct.HashSet.html#method.insert | ||
| // "If the set did not have this value present, `true` is returned." | ||
| Self::Set(set) => { | ||
| if set.insert(v) { | ||
| // again id doesn't matter here as we'll be removing from a set | ||
| Some(0) | ||
| } else { | ||
| None | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
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||
| pub fn remove(&mut self, v: &T, index: usize) { | ||
| match self { | ||
| Self::Array(array) => { | ||
| debug_assert!(array[index].as_ref() == Some(v), "remove did not match insert"); | ||
| array[index] = None; | ||
| } | ||
| Self::Set(set) => { | ||
| set.remove(v); | ||
| } | ||
| } | ||
| } | ||
| } | ||
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