Lock Free Object Pool

A thread-safe object pool collection with automatic return.

Some implementations are lockfree :

• LinearObjectPool
• SpinLockObjectPool

Other use std::Mutex :

• MutexObjectPool

And NoneObjectPool basic allocation without pool.

Usage

[dependencies]
lockfree-object-pool = "0.1"

extern crate lockfree_object_pool;

Example

The general pool creation looks like this for

 let pool = LinearObjectPool::<u32>::new(
     ||  Default::default(), 
     |v| {*v = 0; });

And use the object pool

  let mut item = pool.pull();
  *item = 5;
  ...  

At the end of the scope item return in object pool.

Interface

All implementations support same interface :

struct ObjectPool<T> {  
}

impl<T> ObjectPool<T> {
  // for LinearObjectPool, SpinLockObjectPool and MutexObjectPool
  // init closure used to create an element
  // reset closure used to reset element a dropped element
  pub fn new<R, I>(init: I, reset: R) -> Self
    where
        R: Fn(&mut T) + 'static + Send + Sync,
        I: Fn() -> T + 'static + Send + Sync + Clone,
    {
      ...
    }

  // for NoneObjectPool
  // init closure used to create an element
  pub fn new<I>(init: I) -> Self
    where
        I: Fn() -> T + 'static
    {
      ...
    }

  pub fn pull(&self) -> Reusable<T> {
    ...
  }

  pub fn pull_owned(self: &Arc<Self>) -> OwnedReusable<T> {
    ...
  }
}

struct Reusable<T> {  
}

impl<'a, T> DerefMut for Reusable<'a, T> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        ...
    }
}

impl<'a, T> Deref for Reusable<'a, T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        ...
    }
}

struct OwnedReusable<T> {  
}

impl<'a, T> DerefMut for OwnedReusable<'a, T> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        ...
    }
}

impl<'a, T> Deref for OwnedReusable<'a, T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        ...
    }
}

Multithreading

All implementation support allocation/desallocation from on or more thread. You only need to wrap the pool in a [std::sync::Arc] :

 let pool = Arc::new(LinearObjectPool::<u32>::new(
     ||  Default::default(), 
     |v| {*v = 0; }));

Performance

Global report.

Allocation

ObjectPool	Duration in Monothreading (us)	Duration Multithreading (us)
NoneObjectPool	1.2848	0.62509
MutexObjectPool	1.3107	1.5178
SpinLockObjectPool	1.3106	1.3684
LinearObjectPool	0.23732	0.38913
crate 'sharded-slab'	1.6264	0.82607
crate 'object-pool'	0.77533	0.26224

Report monothreading and multithreading

Forward Message between Thread

ObjectPool	1 Reader - 1 Writter (ns)	5 Reader - 1 Writter (ns)	1 Reader - 5 Writter (ns)	5 Reader - 5 Writter (ns)
NoneObjectPool	529.75	290.47	926.05	722.35
MutexObjectPool	429.29	207.17	909.88	409.99
SpinLockObjectPool	34.277	182.62	1089.7	483.81
LinearObjectPool	43.876	163.18	365.56	326.92
crate 'sharded-slab'	525.82	775.79	966.87	1289.2

Not supported by crate 'object-pool'

Report 1-1, 5-1, 1-5 , 5-5

Desallocation

ObjectPool	Duration in Monothreading (ns)	Duration Multithreading (ns)
NoneObjectPool	111.81	93.585
MutexObjectPool	26.108	101.86
SpinLockObjectPool	22.441	50.107
LinearObjectPool	7.5379	41.707
crate 'sharded-slab'	7.0394	10.283
crate 'object-pool'	20.517	44.798

Report monothreading and multithreading

Comparison with Similar Crates

• crate 'sharded-slab': I like pull interface but i dislike

  • Default / Reset trait because not enough flexible
  • Performance
  • create_owned method not use a reference on Self

• crate 'object-pool': use a spinlock to sync and the performance are pretty good but i dislike :

  • need to specify fallback at each pull call :

  use object_pool::Pool;
  let pool = Pool::<Vec<u8>>::new(32, || Vec::with_capacity(4096);
  // ...
  let item1 = pool.pull(|| Vec::with_capacity(4096));
  // ...
  let item2 = pool.pull(|| Vec::with_capacity(4096));

  • no reset mechanism, need to do manually
  • no possiblity to forward data between thread

TODO

• why the object-pool with spinlock has so bad performance compared to spinlock mutex use by crate 'object-pool'
• impl a tree object pool (cf toolsbox)

Implementation detail

TODO

Licence

cf Boost Licence

Related Projects

• crate 'object-pool' - A thread-safe object pool in rust with mutex
• crate 'sharded-slab' - A lock-free concurrent slab
• toolsbox - Some object pool implementation en c++