Reduce maximum LRU size to 2^16 entries, reducing memory footprint of LRU entries

crates/base-db/src/lib.rs

@@ -42,9 +42,9 @@ pub trait Upcast<T: ?Sized> {
     fn upcast(&self) -> &T;
 }
 
-pub const DEFAULT_FILE_TEXT_LRU_CAP: usize = 16;
-pub const DEFAULT_PARSE_LRU_CAP: usize = 128;
-pub const DEFAULT_BORROWCK_LRU_CAP: usize = 2024;
+pub const DEFAULT_FILE_TEXT_LRU_CAP: u16 = 16;
+pub const DEFAULT_PARSE_LRU_CAP: u16 = 128;
+pub const DEFAULT_BORROWCK_LRU_CAP: u16 = 2024;
 
 pub trait FileLoader {
     /// Text of the file.

crates/ide-db/src/lib.rs

@@ -145,7 +145,7 @@ impl Default for RootDatabase {
 }
 
 impl RootDatabase {
-    pub fn new(lru_capacity: Option<usize>) -> RootDatabase {
+    pub fn new(lru_capacity: Option<u16>) -> RootDatabase {
         let mut db = RootDatabase { storage: ManuallyDrop::new(salsa::Storage::default()) };
         db.set_crate_graph_with_durability(Default::default(), Durability::HIGH);
         db.set_proc_macros_with_durability(Default::default(), Durability::HIGH);
@@ -161,7 +161,7 @@ impl RootDatabase {
         self.set_expand_proc_attr_macros_with_durability(true, Durability::HIGH);
     }
 
-    pub fn update_base_query_lru_capacities(&mut self, lru_capacity: Option<usize>) {
+    pub fn update_base_query_lru_capacities(&mut self, lru_capacity: Option<u16>) {
         let lru_capacity = lru_capacity.unwrap_or(base_db::DEFAULT_PARSE_LRU_CAP);
         base_db::FileTextQuery.in_db_mut(self).set_lru_capacity(DEFAULT_FILE_TEXT_LRU_CAP);
         base_db::ParseQuery.in_db_mut(self).set_lru_capacity(lru_capacity);
@@ -170,7 +170,7 @@ impl RootDatabase {
         hir::db::BorrowckQuery.in_db_mut(self).set_lru_capacity(base_db::DEFAULT_BORROWCK_LRU_CAP);
     }
 
-    pub fn update_lru_capacities(&mut self, lru_capacities: &FxHashMap<Box<str>, usize>) {
+    pub fn update_lru_capacities(&mut self, lru_capacities: &FxHashMap<Box<str>, u16>) {
         use hir::db as hir_db;
 
         base_db::FileTextQuery.in_db_mut(self).set_lru_capacity(DEFAULT_FILE_TEXT_LRU_CAP);

crates/ide/src/lib.rs

@@ -161,7 +161,7 @@ pub struct AnalysisHost {
 }
 
 impl AnalysisHost {
-    pub fn new(lru_capacity: Option<usize>) -> AnalysisHost {
+    pub fn new(lru_capacity: Option<u16>) -> AnalysisHost {
         AnalysisHost { db: RootDatabase::new(lru_capacity) }
     }
 
@@ -169,11 +169,11 @@ impl AnalysisHost {
         AnalysisHost { db }
     }
 
-    pub fn update_lru_capacity(&mut self, lru_capacity: Option<usize>) {
+    pub fn update_lru_capacity(&mut self, lru_capacity: Option<u16>) {
         self.db.update_base_query_lru_capacities(lru_capacity);
     }
 
-    pub fn update_lru_capacities(&mut self, lru_capacities: &FxHashMap<Box<str>, usize>) {
+    pub fn update_lru_capacities(&mut self, lru_capacities: &FxHashMap<Box<str>, u16>) {
         self.db.update_lru_capacities(lru_capacities);
     }
 

crates/load-cargo/src/lib.rs

@@ -379,7 +379,7 @@ fn load_crate_graph(
 ) -> RootDatabase {
     let ProjectWorkspace { toolchain, target_layout, .. } = ws;
 
-    let lru_cap = std::env::var("RA_LRU_CAP").ok().and_then(|it| it.parse::<usize>().ok());
+    let lru_cap = std::env::var("RA_LRU_CAP").ok().and_then(|it| it.parse::<u16>().ok());
     let mut db = RootDatabase::new(lru_cap);
     let mut analysis_change = ChangeWithProcMacros::new();
 

crates/rust-analyzer/src/config.rs

@@ -283,9 +283,9 @@ config_data! {
         linkedProjects: Vec<ManifestOrProjectJson> = vec![],
 
         /// Number of syntax trees rust-analyzer keeps in memory. Defaults to 128.
-        lru_capacity: Option<usize>                 = None,
+        lru_capacity: Option<u16>                 = None,
         /// Sets the LRU capacity of the specified queries.
-        lru_query_capacities: FxHashMap<Box<str>, usize> = FxHashMap::default(),
+        lru_query_capacities: FxHashMap<Box<str>, u16> = FxHashMap::default(),
 
         /// These proc-macros will be ignored when trying to expand them.
         ///
@@ -1606,11 +1606,11 @@ impl Config {
         extra_env
     }
 
-    pub fn lru_parse_query_capacity(&self) -> Option<usize> {
+    pub fn lru_parse_query_capacity(&self) -> Option<u16> {
         self.lru_capacity().to_owned()
     }
 
-    pub fn lru_query_capacities_config(&self) -> Option<&FxHashMap<Box<str>, usize>> {
+    pub fn lru_query_capacities_config(&self) -> Option<&FxHashMap<Box<str>, u16>> {
         self.lru_query_capacities().is_empty().not().then(|| self.lru_query_capacities())
     }
 

crates/salsa/src/derived.rs

@@ -203,7 +203,7 @@ where
     Q: QueryFunction,
     MP: MemoizationPolicy<Q>,
 {
-    fn set_lru_capacity(&self, new_capacity: usize) {
+    fn set_lru_capacity(&self, new_capacity: u16) {
         self.lru_list.set_lru_capacity(new_capacity);
     }
 }

crates/salsa/src/lib.rs

@@ -577,7 +577,7 @@ where
     /// cost of potential extra recalculations of evicted values.
     ///
     /// If `cap` is zero, all values are preserved, this is the default.
-    pub fn set_lru_capacity(&self, cap: usize)
+    pub fn set_lru_capacity(&self, cap: u16)
     where
         Q::Storage: plumbing::LruQueryStorageOps,
     {

crates/salsa/src/lru.rs

@@ -1,7 +1,7 @@
 use oorandom::Rand64;
 use parking_lot::Mutex;
 use std::fmt::Debug;
-use std::sync::atomic::AtomicUsize;
+use std::sync::atomic::AtomicU16;
 use std::sync::atomic::Ordering;
 use triomphe::Arc;
 
@@ -20,15 +20,15 @@ pub(crate) struct Lru<Node>
 where
     Node: LruNode,
 {
-    green_zone: AtomicUsize,
+    green_zone: AtomicU16,
     data: Mutex<LruData<Node>>,
 }
 
 #[derive(Debug)]
 struct LruData<Node> {
-    end_red_zone: usize,
-    end_yellow_zone: usize,
-    end_green_zone: usize,
+    end_red_zone: u16,
+    end_yellow_zone: u16,
+    end_green_zone: u16,
     rng: Rand64,
     entries: Vec<Arc<Node>>,
 }
@@ -39,9 +39,9 @@ pub(crate) trait LruNode: Sized + Debug {
 
 #[derive(Debug)]
 pub(crate) struct LruIndex {
-    /// Index in the appropriate LRU list, or std::usize::MAX if not a
+    /// Index in the appropriate LRU list, or std::u16::MAX if not a
     /// member.
-    index: AtomicUsize,
+    index: AtomicU16,
 }
 
 impl<Node> Default for Lru<Node>
@@ -68,12 +68,12 @@ where
 
     #[cfg_attr(not(test), allow(dead_code))]
     fn with_seed(seed: &str) -> Self {
-        Lru { green_zone: AtomicUsize::new(0), data: Mutex::new(LruData::with_seed(seed)) }
+        Lru { green_zone: AtomicU16::new(0), data: Mutex::new(LruData::with_seed(seed)) }
     }
 
     /// Adjust the total number of nodes permitted to have a value at
     /// once.  If `len` is zero, this disables LRU caching completely.
-    pub(crate) fn set_lru_capacity(&self, len: usize) {
+    pub(crate) fn set_lru_capacity(&self, len: u16) {
         let mut data = self.data.lock();
 
         // We require each zone to have at least 1 slot. Therefore,
@@ -143,23 +143,24 @@ where
         LruData { end_yellow_zone: 0, end_green_zone: 0, end_red_zone: 0, entries: Vec::new(), rng }
     }
 
-    fn green_zone(&self) -> std::ops::Range<usize> {
+    fn green_zone(&self) -> std::ops::Range<u16> {
         0..self.end_green_zone
     }
 
-    fn yellow_zone(&self) -> std::ops::Range<usize> {
+    fn yellow_zone(&self) -> std::ops::Range<u16> {
         self.end_green_zone..self.end_yellow_zone
     }
 
-    fn red_zone(&self) -> std::ops::Range<usize> {
+    fn red_zone(&self) -> std::ops::Range<u16> {
         self.end_yellow_zone..self.end_red_zone
     }
 
-    fn resize(&mut self, len_green_zone: usize, len_yellow_zone: usize, len_red_zone: usize) {
+    fn resize(&mut self, len_green_zone: u16, len_yellow_zone: u16, len_red_zone: u16) {
         self.end_green_zone = len_green_zone;
         self.end_yellow_zone = self.end_green_zone + len_yellow_zone;
         self.end_red_zone = self.end_yellow_zone + len_red_zone;
-        let entries = std::mem::replace(&mut self.entries, Vec::with_capacity(self.end_red_zone));
+        let entries =
+            std::mem::replace(&mut self.entries, Vec::with_capacity(self.end_red_zone as usize));
 
         tracing::debug!("green_zone = {:?}", self.green_zone());
         tracing::debug!("yellow_zone = {:?}", self.yellow_zone());
@@ -207,7 +208,7 @@ where
 
         // Easy case: we still have capacity. Push it, and then promote
         // it up to the appropriate zone.
-        let len = self.entries.len();
+        let len = self.entries.len() as u16;
         if len < self.end_red_zone {
             self.entries.push(node.clone());
             node.lru_index().store(len);
@@ -218,7 +219,7 @@ where
         // Harder case: no capacity. Create some by evicting somebody from red
         // zone and then promoting.
         let victim_index = self.pick_index(self.red_zone());
-        let victim_node = std::mem::replace(&mut self.entries[victim_index], node.clone());
+        let victim_node = std::mem::replace(&mut self.entries[victim_index as usize], node.clone());
         tracing::debug!("evicting red node {:?} from {}", victim_node, victim_index);
         victim_node.lru_index().clear();
         self.promote_red_to_green(node, victim_index);
@@ -231,7 +232,7 @@ where
     ///
     /// NB: It is not required that `node.lru_index()` is up-to-date
     /// when entering this method.
-    fn promote_red_to_green(&mut self, node: &Arc<Node>, red_index: usize) {
+    fn promote_red_to_green(&mut self, node: &Arc<Node>, red_index: u16) {
         debug_assert!(self.red_zone().contains(&red_index));
 
         // Pick a yellow at random and switch places with it.
@@ -242,12 +243,12 @@ where
         let yellow_index = self.pick_index(self.yellow_zone());
         tracing::debug!(
             "demoting yellow node {:?} from {} to red at {}",
-            self.entries[yellow_index],
+            self.entries[yellow_index as usize],
             yellow_index,
             red_index,
         );
-        self.entries.swap(yellow_index, red_index);
-        self.entries[red_index].lru_index().store(red_index);
+        self.entries.swap(yellow_index as usize, red_index as usize);
+        self.entries[red_index as usize].lru_index().store(red_index);
 
         // Now move ourselves up into the green zone.
         self.promote_yellow_to_green(node, yellow_index);
@@ -259,51 +260,51 @@ where
     ///
     /// NB: It is not required that `node.lru_index()` is up-to-date
     /// when entering this method.
-    fn promote_yellow_to_green(&mut self, node: &Arc<Node>, yellow_index: usize) {
+    fn promote_yellow_to_green(&mut self, node: &Arc<Node>, yellow_index: u16) {
         debug_assert!(self.yellow_zone().contains(&yellow_index));
 
         // Pick a yellow at random and switch places with it.
         let green_index = self.pick_index(self.green_zone());
         tracing::debug!(
             "demoting green node {:?} from {} to yellow at {}",
-            self.entries[green_index],
+            self.entries[green_index as usize],
             green_index,
             yellow_index
         );
-        self.entries.swap(green_index, yellow_index);
-        self.entries[yellow_index].lru_index().store(yellow_index);
+        self.entries.swap(green_index as usize, yellow_index as usize);
+        self.entries[yellow_index as usize].lru_index().store(yellow_index);
         node.lru_index().store(green_index);
 
         tracing::debug!("promoted {:?} to green index {}", node, green_index);
     }
 
-    fn pick_index(&mut self, zone: std::ops::Range<usize>) -> usize {
-        let end_index = std::cmp::min(zone.end, self.entries.len());
-        self.rng.rand_range(zone.start as u64..end_index as u64) as usize
+    fn pick_index(&mut self, zone: std::ops::Range<u16>) -> u16 {
+        let end_index = std::cmp::min(zone.end, self.entries.len() as u16);
+        self.rng.rand_range(zone.start as u64..end_index as u64) as u16
     }
 }
 
 impl Default for LruIndex {
     fn default() -> Self {
-        Self { index: AtomicUsize::new(usize::MAX) }
+        Self { index: AtomicU16::new(u16::MAX) }
     }
 }
 
 impl LruIndex {
-    fn load(&self) -> usize {
+    fn load(&self) -> u16 {
         self.index.load(Ordering::Acquire) // see note on ordering below
     }
 
-    fn store(&self, value: usize) {
+    fn store(&self, value: u16) {
         self.index.store(value, Ordering::Release) // see note on ordering below
     }
 
     fn clear(&self) {
-        self.store(usize::MAX);
+        self.store(u16::MAX);
     }
 
     fn is_in_lru(&self) -> bool {
-        self.load() != usize::MAX
+        self.load() != u16::MAX
     }
 }
 

crates/salsa/src/plumbing.rs

@@ -228,7 +228,7 @@ where
 /// that is, storage whose value is not derived from other storage but
 /// is set independently.
 pub trait LruQueryStorageOps {
-    fn set_lru_capacity(&self, new_capacity: usize);
+    fn set_lru_capacity(&self, new_capacity: u16);
 }
 
 pub trait DerivedQueryStorageOps<Q>