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Diffstat (limited to 'tokio/src/util/slab/page.rs')
| -rw-r--r-- | tokio/src/util/slab/page.rs | 187 |
1 files changed, 0 insertions, 187 deletions
diff --git a/tokio/src/util/slab/page.rs b/tokio/src/util/slab/page.rs deleted file mode 100644 index 0000e934..00000000 --- a/tokio/src/util/slab/page.rs +++ /dev/null @@ -1,187 +0,0 @@ -use crate::loom::cell::UnsafeCell; -use crate::util::slab::{Address, Entry, Slot, TransferStack, INITIAL_PAGE_SIZE}; - -use std::fmt; - -/// Data accessed only by the thread that owns the shard. -pub(crate) struct Local { - head: UnsafeCell<usize>, -} - -/// Data accessed by any thread. -pub(crate) struct Shared<T> { - remote: TransferStack, - size: usize, - prev_sz: usize, - slab: UnsafeCell<Option<Box<[Slot<T>]>>>, -} - -/// Returns the size of the page at index `n` -pub(super) fn size(n: usize) -> usize { - INITIAL_PAGE_SIZE << n -} - -impl Local { - pub(crate) fn new() -> Self { - Self { - head: UnsafeCell::new(0), - } - } - - fn head(&self) -> usize { - self.head.with(|head| unsafe { *head }) - } - - fn set_head(&self, new_head: usize) { - self.head.with_mut(|head| unsafe { - *head = new_head; - }) - } -} - -impl<T: Entry> Shared<T> { - pub(crate) fn new(size: usize, prev_sz: usize) -> Shared<T> { - Self { - prev_sz, - size, - remote: TransferStack::new(), - slab: UnsafeCell::new(None), - } - } - - /// Allocates storage for this page if it does not allready exist. - /// - /// This requires unique access to the page (e.g. it is called from the - /// thread that owns the page, or, in the case of `SingleShard`, while the - /// lock is held). In order to indicate this, a reference to the page's - /// `Local` data is taken by this function; the `Local` argument is not - /// actually used, but requiring it ensures that this is only called when - /// local access is held. - #[cold] - fn alloc_page(&self, _: &Local) { - debug_assert!(self.slab.with(|s| unsafe { (*s).is_none() })); - - let mut slab = Vec::with_capacity(self.size); - slab.extend((1..self.size).map(Slot::new)); - slab.push(Slot::new(Address::NULL)); - - self.slab.with_mut(|s| { - // this mut access is safe — it only occurs to initially - // allocate the page, which only happens on this thread; if the - // page has not yet been allocated, other threads will not try - // to access it yet. - unsafe { - *s = Some(slab.into_boxed_slice()); - } - }); - } - - pub(crate) fn alloc(&self, local: &Local) -> Option<Address> { - let head = local.head(); - - // are there any items on the local free list? (fast path) - let head = if head < self.size { - head - } else { - // if the local free list is empty, pop all the items on the remote - // free list onto the local free list. - self.remote.pop_all()? - }; - - // if the head is still null, both the local and remote free lists are - // empty --- we can't fit any more items on this page. - if head == Address::NULL { - return None; - } - - // do we need to allocate storage for this page? - let page_needs_alloc = self.slab.with(|s| unsafe { (*s).is_none() }); - if page_needs_alloc { - self.alloc_page(local); - } - - let gen = self.slab.with(|slab| { - let slab = unsafe { &*(slab) } - .as_ref() - .expect("page must have been allocated to alloc!"); - - let slot = &slab[head]; - - local.set_head(slot.next()); - slot.generation() - }); - - let index = head + self.prev_sz; - - Some(Address::new(index, gen)) - } - - pub(crate) fn get(&self, addr: Address) -> Option<&T> { - let page_offset = addr.slot() - self.prev_sz; - - self.slab - .with(|slab| unsafe { &*slab }.as_ref()?.get(page_offset)) - .map(|slot| slot.get()) - } - - pub(crate) fn remove_local(&self, local: &Local, addr: Address) { - let offset = addr.slot() - self.prev_sz; - - self.slab.with(|slab| { - let slab = unsafe { &*slab }.as_ref(); - - let slot = if let Some(slot) = slab.and_then(|slab| slab.get(offset)) { - slot - } else { - return; - }; - - if slot.reset(addr.generation()) { - slot.set_next(local.head()); - local.set_head(offset); - } - }) - } - - pub(crate) fn remove_remote(&self, addr: Address) { - let offset = addr.slot() - self.prev_sz; - - self.slab.with(|slab| { - let slab = unsafe { &*slab }.as_ref(); - - let slot = if let Some(slot) = slab.and_then(|slab| slab.get(offset)) { - slot - } else { - return; - }; - - if !slot.reset(addr.generation()) { - return; - } - - self.remote.push(offset, |next| slot.set_next(next)); - }) - } -} - -impl fmt::Debug for Local { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - self.head.with(|head| { - let head = unsafe { *head }; - f.debug_struct("Local") - .field("head", &format_args!("{:#0x}", head)) - .finish() - }) - } -} - -impl<T> fmt::Debug for Shared<T> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_struct("Shared") - .field("remote", &self.remote) - .field("prev_sz", &self.prev_sz) - .field("size", &self.size) - // .field("slab", &self.slab) - .finish() - } -} |