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+#![cfg_attr(not(feature = "rt"), allow(dead_code))]
+
+use crate::loom::cell::UnsafeCell;
+use crate::loom::sync::atomic::{AtomicBool, AtomicUsize};
+use crate::loom::sync::{Arc, Mutex};
+use crate::util::bit;
+use std::fmt;
+use std::mem;
+use std::ops;
+use std::ptr;
+use std::sync::atomic::Ordering::Relaxed;
+
+/// Amortized allocation for homogeneous data types.
+///
+/// The slab pre-allocates chunks of memory to store values. It uses a similar
+/// growing strategy as `Vec`. When new capacity is needed, the slab grows by
+/// 2x.
+///
+/// # Pages
+///
+/// Unlike `Vec`, growing does not require moving existing elements. Instead of
+/// being a continuous chunk of memory for all elements, `Slab` is an array of
+/// arrays. The top-level array is an array of pages. Each page is 2x bigger
+/// than the previous one. When the slab grows, a new page is allocated.
+///
+/// Pages are lazily initialized.
+///
+/// # Allocating
+///
+/// When allocating an object, first previously used slots are reused. If no
+/// previously used slot is available, a new slot is initialized in an existing
+/// page. If all pages are full, then a new page is allocated.
+///
+/// When an allocated object is released, it is pushed into it's page's free
+/// list. Allocating scans all pages for a free slot.
+///
+/// # Indexing
+///
+/// The slab is able to index values using an address. Even when the indexed
+/// object has been released, it is still safe to index. This is a key ability
+/// for using the slab with the I/O driver. Addresses are registered with the
+/// OS's selector and I/O resources can be released without synchronizing with
+/// the OS.
+///
+/// # Compaction
+///
+/// `Slab::compact` will release pages that have been allocated but are no
+/// longer used. This is done by scanning the pages and finding pages with no
+/// allocated objects. These pages are then freed.
+///
+/// # Synchronization
+///
+/// The `Slab` structure is able to provide (mostly) unsynchronized reads to
+/// values stored in the slab. Insertions and removals are synchronized. Reading
+/// objects via `Ref` is fully unsynchronized. Indexing objects uses amortized
+/// synchronization.
+///
+pub(crate) struct Slab<T> {
+ /// Array of pages. Each page is synchronized.
+ pages: [Arc<Page<T>>; NUM_PAGES],
+
+ /// Caches the array pointer & number of initialized slots.
+ cached: [CachedPage<T>; NUM_PAGES],
+}
+
+/// Allocate values in the associated slab.
+pub(crate) struct Allocator<T> {
+ /// Pages in the slab. The first page has a capacity of 16 elements. Each
+ /// following page has double the capacity of the previous page.
+ ///
+ /// Each returned `Ref` holds a reference count to this `Arc`.
+ pages: [Arc<Page<T>>; NUM_PAGES],
+}
+
+/// References a slot in the slab. Indexing a slot using an `Address` is memory
+/// safe even if the slot has been released or the page has been deallocated.
+/// However, it is not guaranteed that the slot has not been reused and is now
+/// represents a different value.
+///
+/// The I/O driver uses a counter to track the slot's generation. Once accessing
+/// the slot, the generations are compared. If they match, the value matches the
+/// address.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub(crate) struct Address(usize);
+
+/// An entry in the slab.
+pub(crate) trait Entry: Default {
+ /// Reset the entry's value and track the generation.
+ fn reset(&self);
+}
+
+/// A reference to a value stored in the slab
+pub(crate) struct Ref<T> {
+ value: *const Value<T>,
+}
+
+/// Maximum number of pages a slab can contain.
+const NUM_PAGES: usize = 19;
+
+/// Minimum number of slots a page can contain.
+const PAGE_INITIAL_SIZE: usize = 32;
+const PAGE_INDEX_SHIFT: u32 = PAGE_INITIAL_SIZE.trailing_zeros() + 1;
+
+/// A page in the slab
+struct Page<T> {
+ /// Slots
+ slots: Mutex<Slots<T>>,
+
+ // Number of slots currently being used. This is not guaranteed to be up to
+ // date and should only be used as a hint.
+ used: AtomicUsize,
+
+ // Set to `true` when the page has been allocated.
+ allocated: AtomicBool,
+
+ // The number of slots the page can hold.
+ len: usize,
+
+ // Length of all previous pages combined
+ prev_len: usize,
+}
+
+struct CachedPage<T> {
+ /// Pointer to the page's slots.
+ slots: *const Slot<T>,
+
+ /// Number of initialized slots.
+ init: usize,
+}
+
+/// Page state
+struct Slots<T> {
+ /// Slots
+ slots: Vec<Slot<T>>,
+
+ head: usize,
+
+ /// Number of slots currently in use.
+ used: usize,
+}
+
+unsafe impl<T: Sync> Sync for Page<T> {}
+unsafe impl<T: Sync> Send for Page<T> {}
+unsafe impl<T: Sync> Sync for CachedPage<T> {}
+unsafe impl<T: Sync> Send for CachedPage<T> {}
+unsafe impl<T: Sync> Sync for Ref<T> {}
+unsafe impl<T: Sync> Send for Ref<T> {}
+
+/// A slot in the slab. Contains slot-specific metadata.
+///
+/// `#[repr(C)]` guarantees that the struct starts w/ `value`. We use pointer
+/// math to map a value pointer to an index in the page.
+#[repr(C)]
+struct Slot<T> {
+ /// Pointed to by `Ref`.
+ value: UnsafeCell<Value<T>>,
+
+ /// Next entry in the free list.
+ next: u32,
+}
+
+/// Value paired with a reference to the page
+struct Value<T> {
+ /// Value stored in the value
+ value: T,
+
+ /// Pointer to the page containing the slot.
+ ///
+ /// A raw pointer is used as this creates a ref cycle.
+ page: *const Page<T>,
+}
+
+impl<T> Slab<T> {
+ /// Create a new, empty, slab
+ pub(crate) fn new() -> Slab<T> {
+ // Initializing arrays is a bit annoying. Instead of manually writing
+ // out an array and every single entry, `Default::default()` is used to
+ // initialize the array, then the array is iterated and each value is
+ // initialized.
+ let mut slab = Slab {
+ pages: Default::default(),
+ cached: Default::default(),
+ };
+
+ let mut len = PAGE_INITIAL_SIZE;
+ let mut prev_len: usize = 0;
+
+ for page in &mut slab.pages {
+ let page = Arc::get_mut(page).unwrap();
+ page.len = len;
+ page.prev_len = prev_len;
+ len *= 2;
+ prev_len += page.len;
+
+ // Ensure we don't exceed the max address space.
+ debug_assert!(
+ page.len - 1 + page.prev_len < (1 << 24),
+ "max = {:b}",
+ page.len - 1 + page.prev_len
+ );
+ }
+
+ slab
+ }
+
+ /// Returns a new `Allocator`.
+ ///
+ /// The `Allocator` supports concurrent allocation of objects.
+ pub(crate) fn allocator(&self) -> Allocator<T> {
+ Allocator {
+ pages: self.pages.clone(),
+ }
+ }
+
+ /// Returns a reference to the value stored at the given address.
+ ///
+ /// `&mut self` is used as the call may update internal cached state.
+ pub(crate) fn get(&mut self, addr: Address) -> Option<&T> {
+ let page_idx = addr.page();
+ let slot_idx = self.pages[page_idx].slot(addr);
+
+ // If the address references a slot that was last seen as uninitialized,
+ // the `CachedPage` is updated. This requires acquiring the page lock
+ // and updating the slot pointer and initialized offset.
+ if self.cached[page_idx].init <= slot_idx {
+ self.cached[page_idx].refresh(&self.pages[page_idx]);
+ }
+
+ // If the address **still** references an uninitialized slot, then the
+ // address is invalid and `None` is returned.
+ if self.cached[page_idx].init <= slot_idx {
+ return None;
+ }
+
+ // Get a reference to the value. The lifetime of the returned reference
+ // is bound to `&self`. The only way to invalidate the underlying memory
+ // is to call `compact()`. The lifetimes prevent calling `compact()`
+ // while references to values are outstanding.
+ //
+ // The referenced data is never mutated. Only `&self` references are
+ // used and the data is `Sync`.
+ Some(self.cached[page_idx].get(slot_idx))
+ }
+
+ /// Calls the given function with a reference to each slot in the slab. The
+ /// slot may not be in-use.
+ ///
+ /// This is used by the I/O driver during the shutdown process to notify
+ /// each pending task.
+ pub(crate) fn for_each(&mut self, mut f: impl FnMut(&T)) {
+ for page_idx in 0..self.pages.len() {
+ // It is required to avoid holding the lock when calling the
+ // provided function. The function may attempt to acquire the lock
+ // itself. If we hold the lock here while calling `f`, a deadlock
+ // situation is possible.
+ //
+ // Instead of iterating the slots directly in `page`, which would
+ // require holding the lock, the cache is updated and the slots are
+ // iterated from the cache.
+ self.cached[page_idx].refresh(&self.pages[page_idx]);
+
+ for slot_idx in 0..self.cached[page_idx].init {
+ f(self.cached[page_idx].get(slot_idx));
+ }
+ }
+ }
+
+ // Release memory back to the allocator.
+ //
+ // If pages are empty, the underlying memory is released back to the
+ // allocator.
+ pub(crate) fn compact(&mut self) {
+ // Iterate each page except the very first one. The very first page is
+ // never freed.
+ for (idx, page) in self.pages.iter().enumerate().skip(1) {
+ if page.used.load(Relaxed) != 0 || !page.allocated.load(Relaxed) {
+ // If the page has slots in use or the memory has not been
+ // allocated then it cannot be compacted.
+ continue;
+ }
+
+ let mut slots = match page.slots.try_lock() {
+ Some(slots) => slots,
+ // If the lock cannot be acquired due to being held by another
+ // thread, don't try to compact the page.
+ _ => continue,
+ };
+
+ if slots.used > 0 || slots.slots.capacity() == 0 {
+ // The page is in use or it has not yet been allocated. Either
+ // way, there is no more work to do.
+ continue;
+ }
+
+ page.allocated.store(false, Relaxed);
+
+ // Remove the slots vector from the page. This is done so that the
+ // freeing process is done outside of the lock's critical section.
+ let vec = mem::replace(&mut slots.slots, vec![]);
+ slots.head = 0;
+
+ // Drop the lock so we can drop the vector outside the lock below.
+ drop(slots);
+
+ debug_assert!(
+ self.cached[idx].slots.is_null() || self.cached[idx].slots == vec.as_ptr(),
+ "cached = {:?}; actual = {:?}",
+ self.cached[idx].slots,
+ vec.as_ptr(),
+ );
+
+ // Clear cache
+ self.cached[idx].slots = ptr::null();
+ self.cached[idx].init = 0;
+
+ drop(vec);
+ }
+ }
+}
+
+impl<T> fmt::Debug for Slab<T> {
+ fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ debug(fmt, "Slab", &self.pages[..])
+ }
+}
+
+impl<T: Entry> Allocator<T> {
+ /// Allocate a new entry and return a handle to the entry.
+ ///
+ /// Scans pages from smallest to biggest, stopping when a slot is found.
+ /// Pages are allocated if necessary.
+ ///
+ /// Returns `None` if the slab is full.
+ pub(crate) fn allocate(&self) -> Option<(Address, Ref<T>)> {
+ // Find the first available slot.
+ for page in &self.pages[..] {
+ if let Some((addr, val)) = Page::allocate(page) {
+ return Some((addr, val));
+ }
+ }
+
+ None
+ }
+}
+
+impl<T> fmt::Debug for Allocator<T> {
+ fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ debug(fmt, "slab::Allocator", &self.pages[..])
+ }
+}
+
+impl<T> ops::Deref for Ref<T> {
+ type Target = T;
+
+ fn deref(&self) -> &T {
+ // Safety: `&mut` is never handed out to the underlying value. The page
+ // is not freed until all `Ref` values are dropped.
+ unsafe { &(*self.value).value }
+ }
+}
+
+impl<T> Drop for Ref<T> {
+ fn drop(&mut self) {
+ // Safety: `&mut` is never handed out to the underlying value. The page
+ // is not freed until all `Ref` values are dropped.
+ let _ = unsafe { (*self.value).release() };
+ }
+}
+
+impl<T: fmt::Debug> fmt::Debug for Ref<T> {
+ fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+ (**self).fmt(fmt)
+ }
+}
+
+impl<T: Entry> Page<T> {
+ // Allocates an object, returns the ref and address.
+ //
+ // `self: &Arc<Page<T>>` is avoided here as this would not work with the
+ // loom `Arc`.
+ fn allocate(me: &Arc<Page<T>>) -> Option<(Address, Ref<T>)> {
+ // Before acquiring the lock, use the `used` hint.
+ if me.used.load(Relaxed) == me.len {
+ return None;
+ }
+
+ // Allocating objects requires synchronization
+ let mut locked = me.slots.lock();
+
+ if locked.head < locked.slots.len() {
+ // Re-use an already initialized slot.
+ //
+ // Help out the borrow checker
+ let locked = &mut *locked;
+
+ // Get the index of the slot at the head of the free stack. This is
+ // the slot that will be reused.
+ let idx = locked.head;
+ let slot = &locked.slots[idx];
+
+ // Update the free stack head to point to the next slot.
+ locked.head = slot.next as usize;
+
+ // Increment the number of used slots
+ locked.used += 1;
+ me.used.store(locked.used, Relaxed);
+
+ // Reset the slot
+ slot.value.with(|ptr| unsafe { (*ptr).value.reset() });
+
+ // Return a reference to the slot
+ Some((me.addr(idx), slot.gen_ref(me)))
+ } else if me.len == locked.slots.len() {
+ // The page is full
+ None
+ } else {
+ // No initialized slots are available, but the page has more
+ // capacity. Initialize a new slot.
+ let idx = locked.slots.len();
+
+ if idx == 0 {
+ // The page has not yet been allocated. Allocate the storage for
+ // all page slots.
+ locked.slots.reserve_exact(me.len);
+ }
+
+ // Initialize a new slot
+ locked.slots.push(Slot {
+ value: UnsafeCell::new(Value {
+ value: Default::default(),
+ page: &**me as *const _,
+ }),
+ next: 0,
+ });
+
+ // Increment the head to indicate the free stack is empty
+ locked.head += 1;
+
+ // Increment the number of used slots
+ locked.used += 1;
+ me.used.store(locked.used, Relaxed);
+ me.allocated.store(true, Relaxed);
+
+ debug_assert_eq!(locked.slots.len(), locked.head);
+
+ Some((me.addr(idx), locked.slots[idx].gen_ref(me)))
+ }
+ }
+}
+
+impl<T> Page<T> {
+ /// Returns the slot index within the current page referenced by the given
+ /// address.
+ fn slot(&self, addr: Address) -> usize {
+ addr.0 - self.prev_len
+ }
+
+ /// Returns the address for the given slot
+ fn addr(&self, slot: usize) -> Address {
+ Address(slot + self.prev_len)
+ }
+}
+
+impl<T> Default for Page<T> {
+ fn default() -> Page<T> {
+ Page {
+ used: AtomicUsize::new(0),
+ allocated: AtomicBool::new(false),
+ slots: Mutex::new(Slots {
+ slots: Vec::new(),
+ head: 0,
+ used: 0,
+ }),
+ len: 0,
+ prev_len: 0,
+ }
+ }
+}
+
+impl<T> Page<T> {
+ /// Release a slot into the page's free list
+ fn release(&self, value: *const Value<T>) {
+ let mut locked = self.slots.lock();
+
+ let idx = locked.index_for(value);
+ locked.slots[idx].next = locked.head as u32;
+ locked.head = idx;
+ locked.used -= 1;
+
+ self.used.store(locked.used, Relaxed);
+ }
+}
+
+impl<T> CachedPage<T> {
+ /// Refresh the cache
+ fn refresh(&mut self, page: &Page<T>) {
+ let slots = page.slots.lock();
+
+ if !slots.slots.is_empty() {
+ self.slots = slots.slots.as_ptr();
+ self.init = slots.slots.len();
+ }
+ }
+
+ // Get a value by index
+ fn get(&self, idx: usize) -> &T {
+ assert!(idx < self.init);
+
+ // Safety: Pages are allocated concurrently, but are only ever
+ // **deallocated** by `Slab`. `Slab` will always have a more
+ // conservative view on the state of the slot array. Once `CachedPage`
+ // sees a slot pointer and initialized offset, it will remain valid
+ // until `compact()` is called. The `compact()` function also updates
+ // `CachedPage`.
+ unsafe {
+ let slot = self.slots.add(idx);
+ let value = slot as *const Value<T>;
+
+ &(*value).value
+ }
+ }
+}
+
+impl<T> Default for CachedPage<T> {
+ fn default() -> CachedPage<T> {
+ CachedPage {
+ slots: ptr::null(),
+ init: 0,
+ }
+ }
+}
+
+impl<T> Slots<T> {
+ /// Maps a slot pointer to an offset within the current page.
+ ///
+ /// The pointer math removes the `usize` index from the `Ref` struct,
+ /// shrinking the struct to a single pointer size. The contents of the
+ /// function is safe, the resulting `usize` is bounds checked before being
+ /// used.
+ ///
+ /// # Panics
+ ///
+ /// panics if the provided slot pointer is not contained by the page.
+ fn index_for(&self, slot: *const Value<T>) -> usize {
+ use std::mem;
+
+ let base = &self.slots[0] as *const _ as usize;
+
+ assert!(base != 0, "page is unallocated");
+
+ let slot = slot as usize;
+ let width = mem::size_of::<Slot<T>>();
+
+ assert!(slot >= base, "unexpected pointer");
+
+ let idx = (slot - base) / width;
+ assert!(idx < self.slots.len() as usize);
+
+ idx
+ }
+}
+
+impl<T: Entry> Slot<T> {
+ /// Generates a `Ref` for the slot. This involves bumping the page's ref count.
+ fn gen_ref(&self, page: &Arc<Page<T>>) -> Ref<T> {
+ // The ref holds a ref on the page. The `Arc` is forgotten here and is
+ // resurrected in `release` when the `Ref` is dropped. By avoiding to
+ // hold on to an explicit `Arc` value, the struct size of `Ref` is
+ // reduced.
+ mem::forget(page.clone());
+ let slot = self as *const Slot<T>;
+ let value = slot as *const Value<T>;
+
+ Ref { value }
+ }
+}
+
+impl<T> Value<T> {
+ // Release the slot, returning the `Arc<Page<T>>` logically owned by the ref.
+ fn release(&self) -> Arc<Page<T>> {
+ // Safety: called by `Ref`, which owns an `Arc<Page<T>>` instance.
+ let page = unsafe { Arc::from_raw(self.page) };
+ page.release(self as *const _);
+ page
+ }
+}
+
+impl Address {
+ fn page(self) -> usize {
+ // Since every page is twice as large as the previous page, and all page
+ // sizes are powers of two, we can determine the page index that
+ // contains a given address by shifting the address down by the smallest
+ // page size and looking at how many twos places necessary to represent
+ // that number, telling us what power of two page size it fits inside
+ // of. We can determine the number of twos places by counting the number
+ // of leading zeros (unused twos places) in the number's binary
+ // representation, and subtracting that count from the total number of
+ // bits in a word.
+ let slot_shifted = (self.0 + PAGE_INITIAL_SIZE) >> PAGE_INDEX_SHIFT;
+ (bit::pointer_width() - slot_shifted.leading_zeros()) as usize
+ }
+
+ pub(crate) const fn as_usize(self) -> usize {
+ self.0
+ }
+
+ pub(crate) fn from_usize(src: usize) -> Address {
+ Address(src)
+ }
+}
+
+fn debug<T>(fmt: &mut fmt::Formatter<'_>, name: &str, pages: &[Arc<Page<T>>]) -> fmt::Result {
+ let mut capacity = 0;
+ let mut len = 0;
+
+ for page in pages {
+ if page.allocated.load(Relaxed) {
+ capacity += page.len;
+ len += page.used.load(Relaxed);
+ }
+ }
+
+ fmt.debug_struct(name)
+ .field("len", &len)
+ .field("capacity", &capacity)
+ .finish()
+}
+
+#[cfg(all(test, not(loom)))]
+mod test {
+ use super::*;
+ use std::sync::atomic::AtomicUsize;
+ use std::sync::atomic::Ordering::SeqCst;
+
+ struct Foo {
+ cnt: AtomicUsize,
+ id: AtomicUsize,
+ }
+
+ impl Default for Foo {
+ fn default() -> Foo {
+ Foo {
+ cnt: AtomicUsize::new(0),
+ id: AtomicUsize::new(0),
+ }
+ }
+ }
+
+ impl Entry for Foo {
+ fn reset(&self) {
+ self.cnt.fetch_add(1, SeqCst);
+ }
+ }
+
+ #[test]
+ fn insert_remove() {
+ let mut slab = Slab::<Foo>::new();
+ let alloc = slab.allocator();
+
+ let (addr1, foo1) = alloc.allocate().unwrap();
+ foo1.id.store(1, SeqCst);
+ assert_eq!(0, foo1.cnt.load(SeqCst));
+
+ let (addr2, foo2) = alloc.allocate().unwrap();
+ foo2.id.store(2, SeqCst);
+ assert_eq!(0, foo2.cnt.load(SeqCst));
+
+ assert_eq!(1, slab.get(addr1).unwrap().id.load(SeqCst));
+ assert_eq!(2, slab.get(addr2).unwrap().id.load(SeqCst));
+
+ drop(foo1);
+
+ assert_eq!(1, slab.get(addr1).unwrap().id.load(SeqCst));
+
+ let (addr3, foo3) = alloc.allocate().unwrap();
+ assert_eq!(addr3, addr1);
+ assert_eq!(1, foo3.cnt.load(SeqCst));
+ foo3.id.store(3, SeqCst);
+ assert_eq!(3, slab.get(addr3).unwrap().id.load(SeqCst));
+
+ drop(foo2);
+ drop(foo3);
+
+ slab.compact();
+
+ // The first page is never released
+ assert!(slab.get(addr1).is_some());
+ assert!(slab.get(addr2).is_some());
+ assert!(slab.get(addr3).is_some());
+ }
+
+ #[test]
+ fn insert_many() {
+ let mut slab = Slab::<Foo>::new();
+ let alloc = slab.allocator();
+ let mut entries = vec![];
+
+ for i in 0..10_000 {
+ let (addr, val) = alloc.allocate().unwrap();
+ val.id.store(i, SeqCst);
+ entries.push((addr, val));
+ }
+
+ for (i, (addr, v)) in entries.iter().enumerate() {
+ assert_eq!(i, v.id.load(SeqCst));
+ assert_eq!(i, slab.get(*addr).unwrap().id.load(SeqCst));
+ }
+
+ entries.clear();
+
+ for i in 0..10_000 {
+ let (addr, val) = alloc.allocate().unwrap();
+ val.id.store(10_000 - i, SeqCst);
+ entries.push((addr, val));
+ }
+
+ for (i, (addr, v)) in entries.iter().enumerate() {
+ assert_eq!(10_000 - i, v.id.load(SeqCst));
+ assert_eq!(10_000 - i, slab.get(*addr).unwrap().id.load(SeqCst));
+ }
+ }
+
+ #[test]
+ fn insert_drop_reverse() {
+ let mut slab = Slab::<Foo>::new();
+ let alloc = slab.allocator();
+ let mut entries = vec![];
+
+ for i in 0..10_000 {
+ let (addr, val) = alloc.allocate().unwrap();
+ val.id.store(i, SeqCst);
+ entries.push((addr, val));
+ }
+
+ for _ in 0..10 {
+ // Drop 1000 in reverse
+ for _ in 0..1_000 {
+ entries.pop();
+ }
+
+ // Check remaining
+ for (i, (addr, v)) in entries.iter().enumerate() {
+ assert_eq!(i, v.id.load(SeqCst));
+ assert_eq!(i, slab.get(*addr).unwrap().id.load(SeqCst));
+ }
+ }
+ }
+
+ #[test]
+ fn no_compaction_if_page_still_in_use() {
+ let mut slab = Slab::<Foo>::new();
+ let alloc = slab.allocator();
+ let mut entries1 = vec![];
+ let mut entries2 = vec![];
+
+ for i in 0..10_000 {
+ let (addr, val) = alloc.allocate().unwrap();
+ val.id.store(i, SeqCst);
+
+ if i % 2 == 0 {
+ entries1.push((addr, val, i));
+ } else {
+ entries2.push(val);
+ }
+ }
+
+ drop(entries2);
+
+ for (addr, _, i) in &entries1 {
+ assert_eq!(*i, slab.get(*addr).unwrap().id.load(SeqCst));
+ }
+ }
+
+ #[test]
+ fn compact_all() {
+ let mut slab = Slab::<Foo>::new();
+ let alloc = slab.allocator();
+ let mut entries = vec![];
+
+ for _ in 0..2 {
+ entries.clear();
+
+ for i in 0..10_000 {
+ let (addr, val) = alloc.allocate().unwrap();
+ val.id.store(i, SeqCst);
+
+ entries.push((addr, val));
+ }
+
+ let mut addrs = vec![];
+
+ for (addr, _) in entries.drain(..) {
+ addrs.push(addr);
+ }
+
+ slab.compact();
+
+ // The first page is never freed
+ for addr in &addrs[PAGE_INITIAL_SIZE..] {
+ assert!(slab.get(*addr).is_none());
+ }
+ }
+ }
+
+ #[test]
+ fn issue_3014() {
+ let mut slab = Slab::<Foo>::new();
+ let alloc = slab.allocator();
+ let mut entries = vec![];
+
+ for _ in 0..5 {
+ entries.clear();
+
+ // Allocate a few pages + 1
+ for i in 0..(32 + 64 + 128 + 1) {
+ let (addr, val) = alloc.allocate().unwrap();
+ val.id.store(i, SeqCst);
+
+ entries.push((addr, val, i));
+ }
+
+ for (addr, val, i) in &entries {
+ assert_eq!(*i, val.id.load(SeqCst));
+ assert_eq!(*i, slab.get(*addr).unwrap().id.load(SeqCst));
+ }
+
+ // Release the last entry
+ entries.pop();
+
+ // Compact
+ slab.compact();
+
+ // Check all the addresses
+
+ for (addr, val, i) in &entries {
+ assert_eq!(*i, val.id.load(SeqCst));
+ assert_eq!(*i, slab.get(*addr).unwrap().id.load(SeqCst));
+ }
+ }
+ }
+}
generated by cgit v1.2.3 (git 2.25.1) at 2024-07-15 09:27:20 +0000