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//! This module provides single-threaded blink allocator.
use core::{
alloc::Layout,
mem::ManuallyDrop,
ptr::NonNull,
sync::atomic::{AtomicUsize, Ordering},
};
use allocator_api2::alloc::{AllocError, Allocator};
#[cfg(feature = "alloc")]
use allocator_api2::alloc::Global;
use crate::{
api::BlinkAllocator,
arena::{ArenaLocal, ArenaSync},
};
switch_alloc_default! {
/// Multi-threaded blink allocator.
///
/// Blink-allocator is arena-based allocator that
/// allocates memory in growing chunks and serve allocations from them.
/// When chunk is exhausted a new larger chunk is allocated.
///
/// Deallocation is no-op. [`BlinkAllocator`] can be reset
/// to free all chunks except the last one, that will be reused.
///
/// Blink allocator aims to allocate a chunk large enough to
/// serve all allocations between resets.
///
/// A shared and mutable reference to the [`SyncBlinkAlloc`] implement
/// [`Allocator`] trait.
/// When "nightly" feature is enabled, [`Allocator`] trait is
/// [`core::alloc::Allocator`]. Otherwise it is duplicated trait defined
/// in [`allocator-api2`](allocator_api2).
///
/// Resetting blink allocator requires mutable borrow, so it is not possible
/// to do while shared borrow is alive. That matches requirement of
/// [`Allocator`] trait - while [`Allocator`] instance
/// (a shared reference to `BlinkAlloc`) or any of its clones are alive,
/// allocated memory must be valid.
///
/// This version of blink-allocator is multi-threaded.
/// It can be used from multiple threads concurrently to allocate memory.
/// As mutable borrow is required to reset the allocator,
/// it is not possible to do when shared.
/// Internally it uses [`RwLock`] and [`AtomicUsize`] for synchronized
/// interior mutability. [`RwLock`] is only write-locked when new chunk
/// must be allocated. The arena allocation is performed using lock-free
/// algorithm.
///
/// Still it is slower than single-threaded version [`BlinkAlloc`].
///
/// For best of both worlds [`LocalBlinkAlloc`] can be created from
/// this allocator. [`LocalBlinkAlloc`] will allocate chunks from this
/// allocator, but is single-threaded by itself.
///
/// [`RwLock`]: parking_lot::RwLock
/// [`AtomicUsize`]: core::sync::atomic::AtomicUsize
/// [`BlinkAlloc`]: crate::local::BlinkAlloc
/// [`LocalBlinkAlloc`]: crate::sync::LocalBlinkAlloc
///
/// # Example
///
/// ```
/// # #![cfg_attr(feature = "nightly", feature(allocator_api))]
/// # use blink_alloc::SyncBlinkAlloc;
/// # use std::ptr::NonNull;
///
/// let mut blink = SyncBlinkAlloc::new();
/// let layout = std::alloc::Layout::new::<[u32; 8]>();
/// let ptr = blink.allocate(layout).unwrap();
/// let ptr = NonNull::new(ptr.as_ptr() as *mut u8).unwrap(); // Method for this is unstable.
///
/// unsafe {
/// std::ptr::write(ptr.as_ptr().cast(), [1, 2, 3, 4, 5, 6, 7, 8]);
/// }
///
/// blink.reset();
/// ```
///
/// # Example that uses nightly's `allocator_api`
///
/// ```
/// # #![cfg_attr(feature = "nightly", feature(allocator_api))]
/// # use blink_alloc::SyncBlinkAlloc;
/// # use allocator_api2::vec::Vec;
/// # fn main() {
/// let mut blink = SyncBlinkAlloc::new();
/// let mut vec = Vec::new_in(&blink);
/// vec.push(1);
/// vec.extend(1..3);
/// vec.extend(3..10);
/// drop(vec);
/// blink.reset();
/// # }
/// ```
pub struct SyncBlinkAlloc<A: Allocator = +Global> {
arena: ArenaSync,
allocator: A,
max_local_alloc: AtomicUsize,
}
}
impl<A: Allocator> Drop for SyncBlinkAlloc<A> {
fn drop(&mut self) {
unsafe {
self.arena.reset(false, &self.allocator);
}
}
}
#[test]
fn check_sync() {
fn for_sync_alloc<A: Allocator + Sync>() {
fn is_sink<T: Sync>() {}
is_sink::<SyncBlinkAlloc<A>>();
}
for_sync_alloc::<Global>();
}
impl<A> Default for SyncBlinkAlloc<A>
where
A: Allocator + Default,
{
#[inline(always)]
fn default() -> Self {
Self::new_in(Default::default())
}
}
#[cfg(feature = "alloc")]
impl SyncBlinkAlloc<Global> {
/// Creates new blink allocator that uses global allocator
/// to allocate memory chunks.
///
/// See [`SyncBlinkAlloc::new_in`] for using custom allocator.
#[inline(always)]
pub const fn new() -> Self {
SyncBlinkAlloc::new_in(Global)
}
}
impl<A> SyncBlinkAlloc<A>
where
A: Allocator,
{
/// Creates new blink allocator that uses provided allocator
/// to allocate memory chunks.
///
/// See [`SyncBlinkAlloc::new`] for using global allocator.
#[inline(always)]
pub const fn new_in(allocator: A) -> Self {
SyncBlinkAlloc {
arena: ArenaSync::new(),
allocator,
max_local_alloc: AtomicUsize::new(0),
}
}
/// Returns reference to the underlying allocator used by this blink allocator.
#[inline(always)]
pub const fn inner(&self) -> &A {
&self.allocator
}
/// Creates new blink allocator that uses global allocator
/// to allocate memory chunks.
/// With this method you can specify initial chunk size.
///
/// See [`SyncBlinkAlloc::new_in`] for using custom allocator.
#[inline(always)]
pub const fn with_chunk_size_in(chunk_size: usize, allocator: A) -> Self {
SyncBlinkAlloc {
arena: ArenaSync::with_chunk_size(chunk_size),
allocator,
max_local_alloc: AtomicUsize::new(0),
}
}
/// Creates a new thread-local blink allocator proxy
/// that borrows from this multi-threaded allocator.
///
/// The local proxy allocator works faster and
/// allows more consistent memory reuse.
/// It can be recreated without resetting the multi-threaded allocator,
/// allowing [`SyncBlinkAlloc`] to be warm-up and serve all allocations
/// from a single chunk without ever blocking.
///
/// Best works for fork-join style of parallelism.
/// Create a local allocator for each thread/task.
/// Reset after all threads/tasks are finished.
///
/// # Examples
///
/// ```
/// # #![cfg_attr(feature = "nightly", feature(allocator_api))]
/// # use blink_alloc::SyncBlinkAlloc;
/// # use allocator_api2::vec::Vec;
/// # #[cfg(feature = "alloc")] fn main() {
/// let mut blink = SyncBlinkAlloc::new();
/// for _ in 0..3 {
/// for i in 0..16 {
/// std::thread::scope(|_| {
/// let blink = blink.local();
/// let mut vec = Vec::new_in(&blink);
/// vec.push(i);
/// for j in i*2..i*30 {
/// vec.push(j); // Proxy will allocate enough memory to grow vec without reallocating on 2nd iteration and later.
/// }
/// });
/// }
/// blink.reset();
/// }
/// # }
/// # #[cfg(not(feature = "alloc"))] fn main() {}
/// ```
#[inline(always)]
pub fn local(&self) -> LocalBlinkAlloc<A> {
LocalBlinkAlloc {
arena: ArenaLocal::with_chunk_size(self.max_local_alloc.load(Ordering::Relaxed)),
shared: self,
}
}
/// Allocates memory with specified layout from this allocator.
/// If needed it will allocate new chunk using underlying allocator.
/// If chunk allocation fails, it will return `Err`.
#[inline(always)]
pub fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
// Safety:
// Same instance is used for all allocations and resets.
if let Some(ptr) = unsafe { self.arena.alloc_fast(layout) } {
return Ok(ptr);
}
unsafe { self.arena.alloc_slow(layout, &self.allocator) }
}
/// Resizes memory allocation.
/// Potentially happens in-place.
///
/// # Safety
///
/// `ptr` must be a pointer previously returned by [`allocate`](SyncBlinkAlloc::allocate).
/// `old_size` must be in range `layout.size()..=slice.len()`
/// where `layout` is the layout used in the call to [`allocate`](SyncBlinkAlloc::allocate).
/// and `slice` is the slice pointer returned by [`allocate`](SyncBlinkAlloc::allocate).
///
/// On success, the old pointer is invalidated and the new pointer is returned.
/// On error old allocation is still valid.
#[inline(always)]
pub unsafe fn resize(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
if let Some(ptr) = unsafe { self.arena.resize_fast(ptr, old_layout, new_layout) } {
return Ok(ptr);
}
// Safety:
// Same instance is used for all allocations and resets.
// `ptr` was allocated by this allocator.
unsafe {
self.arena
.resize_slow(ptr, old_layout, new_layout, &self.allocator)
}
}
/// Deallocates memory previously allocated from this allocator.
///
/// This call may not actually free memory.
/// All memory is guaranteed to be freed on [`reset`](SyncBlinkAlloc::reset) call.
///
/// # Safety
///
/// `ptr` must be a pointer previously returned by [`allocate`](SyncBlinkAlloc::allocate).
/// `size` must be in range `layout.size()..=slice.len()`
/// where `layout` is the layout used in the call to [`allocate`](SyncBlinkAlloc::allocate).
/// and `slice` is the slice pointer returned by [`allocate`](SyncBlinkAlloc::allocate).
#[inline(always)]
pub unsafe fn deallocate(&self, ptr: NonNull<u8>, size: usize) {
// Safety:
// `ptr` was allocated by this allocator.
unsafe {
self.arena.dealloc(ptr, size);
}
}
/// Resets this allocator, deallocating all chunks except the last one.
/// Last chunk will be reused.
/// With steady memory usage after few iterations
/// one chunk should be sufficient for all allocations between resets.
#[inline(always)]
pub fn reset(&mut self) {
// Safety:
// Same instance is used for all allocations and resets.
unsafe {
self.arena.reset(true, &self.allocator);
}
}
/// Resets this allocator, deallocating all chunks.
#[inline(always)]
pub fn reset_final(&mut self) {
// Safety:
// Same instance is used for all allocations and resets.
unsafe {
self.arena.reset(false, &self.allocator);
}
}
/// Resets this allocator, deallocating all chunks except the last one.
/// Last chunk will be reused.
/// With steady memory usage after few iterations
/// one chunk should be sufficient for all allocations between resets.
///
/// # Safety
///
/// Blink-allocators guarantee that memory can be used while shared
/// borrow to the allocator is held, preventing safe `fn reset` call.
///
/// With this method it becomes caller responsibility to ensure
/// that allocated memory won't be used after reset.
#[inline(always)]
pub unsafe fn reset_unchecked(&self) {
// Safety:
// Same instance is used for all allocations and resets.
unsafe {
self.arena.reset_unchecked(true, &self.allocator);
}
}
/// Unwrap this allocator, returning the underlying allocator.
/// Leaks allocated chunks.
///
/// To deallocate all chunks call [`reset_final`](BlinkAlloc::reset_final) first.
///
/// The second returned value will use global allocator, so
/// use with care if this method is used inside global allocator.
pub fn into_inner(self) -> A {
let me = ManuallyDrop::new(self);
unsafe { core::ptr::read(&me.allocator) }
}
/// Update maximum local allocation size.
/// Can be used by thread-local blink-allocators that use
/// this shared blink-allocator.
#[inline(always)]
pub fn update_max_local_alloc(&self, max_local_alloc: usize) {
self.max_local_alloc
.fetch_max(max_local_alloc, Ordering::Relaxed);
}
}
unsafe impl<A> Allocator for SyncBlinkAlloc<A>
where
A: Allocator,
{
#[inline(always)]
fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
SyncBlinkAlloc::allocate(self, layout)
}
#[inline(always)]
unsafe fn shrink(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
SyncBlinkAlloc::resize(self, ptr, old_layout, new_layout)
}
#[inline(always)]
unsafe fn grow(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
SyncBlinkAlloc::resize(self, ptr, old_layout, new_layout)
}
#[inline(always)]
unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
SyncBlinkAlloc::deallocate(self, ptr, layout.size());
}
}
unsafe impl<A> Allocator for &mut SyncBlinkAlloc<A>
where
A: Allocator,
{
#[inline(always)]
fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
SyncBlinkAlloc::allocate(self, layout)
}
#[inline(always)]
fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
SyncBlinkAlloc::allocate_zeroed(self, layout)
}
#[inline(always)]
unsafe fn shrink(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
SyncBlinkAlloc::resize(self, ptr, old_layout, new_layout)
}
#[inline(always)]
unsafe fn grow(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
SyncBlinkAlloc::resize(self, ptr, old_layout, new_layout)
}
#[inline(always)]
unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
SyncBlinkAlloc::deallocate(self, ptr, layout.size());
}
}
unsafe impl<A> BlinkAllocator for SyncBlinkAlloc<A>
where
A: Allocator,
{
#[inline(always)]
fn reset(&mut self) {
SyncBlinkAlloc::reset(self)
}
}
switch_alloc_default! {
/// Thread-local proxy for [`SyncBlinkAlloc`].
///
/// Using proxy can yield better performance when
/// it is possible to create proxy once to use for many allocations.
///
/// See [`SyncBlinkAlloc::local`] for more details.
pub struct LocalBlinkAlloc<'a, A: Allocator = +Global> {
arena: ArenaLocal,
shared: &'a SyncBlinkAlloc<A>,
}
}
impl<A> Drop for LocalBlinkAlloc<'_, A>
where
A: Allocator,
{
fn drop(&mut self) {
self.shared
.update_max_local_alloc(self.arena.last_chunk_size());
self.arena.reset_leak(false);
}
}
impl<A> LocalBlinkAlloc<'_, A>
where
A: Allocator,
{
/// Allocates memory with specified layout from this allocator.
/// If needed it will allocate new chunk using underlying allocator.
/// If chunk allocation fails, it will return `Err`.
#[inline(always)]
pub fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
// Safety:
// Same instance is used for all allocations and resets.
if let Some(ptr) = unsafe { self.arena.alloc_fast(layout) } {
return Ok(ptr);
}
unsafe { self.arena.alloc_slow(layout, &self.shared) }
}
/// Resizes memory allocation.
/// Potentially happens in-place.
///
/// # Safety
///
/// `ptr` must be a pointer previously returned by [`allocate`](LocalBlinkAlloc::allocate).
/// `old_size` must be in range `layout.size()..=slice.len()`
/// where `layout` is the layout used in the call to [`allocate`](LocalBlinkAlloc::allocate).
/// and `slice` is the slice pointer returned by [`allocate`](LocalBlinkAlloc::allocate).
///
/// On success, the old pointer is invalidated and the new pointer is returned.
/// On error old allocation is still valid.
#[inline(always)]
pub unsafe fn resize(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
if let Some(ptr) = unsafe { self.arena.resize_fast(ptr, old_layout, new_layout) } {
return Ok(ptr);
}
// Safety:
// Same instance is used for all allocations and resets.
// `ptr` was allocated by this allocator.
unsafe {
self.arena
.resize_slow(ptr, old_layout, new_layout, &self.shared)
}
}
/// Deallocates memory previously allocated from this allocator.
///
/// This call may not actually free memory.
/// All memory is guaranteed to be freed on [`reset`](LocalBlinkAlloc::reset) call.
///
/// # Safety
///
/// `ptr` must be a pointer previously returned by [`allocate`](LocalBlinkAlloc::allocate).
/// `size` must be in range `layout.size()..=slice.len()`
/// where `layout` is the layout used in the call to [`allocate`](LocalBlinkAlloc::allocate).
/// and `slice` is the slice pointer returned by [`allocate`](LocalBlinkAlloc::allocate).
#[inline(always)]
pub unsafe fn deallocate(&self, ptr: NonNull<u8>, size: usize) {
// Safety:
// `ptr` was allocated by this allocator.
unsafe {
self.arena.dealloc(ptr, size);
}
}
/// Resets this allocator, deallocating all chunks except the last one.
/// Last chunk will be reused.
/// With steady memory usage after few iterations
/// one chunk should be sufficient for all allocations between resets.
#[inline(always)]
pub fn reset(&mut self) {
self.shared
.update_max_local_alloc(self.arena.last_chunk_size());
self.arena.reset_leak(true);
}
/// Resets this allocator, deallocating all chunks except the last one.
/// Last chunk will be reused.
/// With steady memory usage after few iterations
/// one chunk should be sufficient for all allocations between resets.
///
/// # Safety
///
/// Blink-allocators guarantee that memory can be used while shared
/// borrow to the allocator is held, preventing safe `fn reset` call.
///
/// With this method it becomes caller responsibility to ensure
/// that allocated memory won't be used after reset.
#[inline(always)]
pub unsafe fn reset_unchecked(&self) {
// Safety:
// Same instance is used for all allocations and resets.
unsafe {
self.arena.reset_unchecked(true, self.shared);
}
}
}
unsafe impl<A> Allocator for LocalBlinkAlloc<'_, A>
where
A: Allocator,
{
#[inline(always)]
fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
LocalBlinkAlloc::allocate(self, layout)
}
#[inline(always)]
unsafe fn shrink(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
LocalBlinkAlloc::resize(self, ptr, old_layout, new_layout)
}
#[inline(always)]
unsafe fn grow(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
LocalBlinkAlloc::resize(self, ptr, old_layout, new_layout)
}
#[inline(always)]
unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
LocalBlinkAlloc::deallocate(self, ptr, layout.size())
}
}
unsafe impl<A> Allocator for &mut LocalBlinkAlloc<'_, A>
where
A: Allocator,
{
#[inline(always)]
fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
LocalBlinkAlloc::allocate(self, layout)
}
#[inline(always)]
fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
LocalBlinkAlloc::allocate_zeroed(self, layout)
}
#[inline(always)]
unsafe fn shrink(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
LocalBlinkAlloc::resize(self, ptr, old_layout, new_layout)
}
#[inline(always)]
unsafe fn grow(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
LocalBlinkAlloc::resize(self, ptr, old_layout, new_layout)
}
#[inline(always)]
unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
LocalBlinkAlloc::deallocate(self, ptr, layout.size())
}
}
unsafe impl<A> BlinkAllocator for LocalBlinkAlloc<'_, A>
where
A: Allocator,
{
#[inline(always)]
fn reset(&mut self) {
LocalBlinkAlloc::reset(self)
}
}