lifeguard

对象池管理器

API 文档

示例

Pool 保留在智能指针中拥有的值。

extern crate lifeguard;
use lifeguard::*;

fn main() {
    let pool : Pool<String> = pool().with(StartingSize(10)).build();
    {
        let string = pool.new_from("Hello, World!"); // Remove a value from the pool
        assert_eq!(9, pool.size());
    } // Values that have gone out of scope are automatically moved back into the pool.
    assert_eq!(10, pool.size());
}

从池中取出的值可以解引用以访问/修改其内容。

extern crate lifeguard;
use lifeguard::*;

fn main() {
    let pool : Pool<String> = pool().with(StartingSize(10)).build();
    let mut string = pool.new_from("cat");
    string.push_str("s love eating mice"); //string.as_mut() also works
    assert_eq!("cats love eating mice", *string);
}

值可以被解包，从池中分离。

extern crate lifeguard;
use lifeguard::*;

fn main() {
    let pool : Pool<String> = pool().with(StartingSize(10)).build();
    {
        let string : String = pool.new().detach();
    } // The String goes out of scope and is dropped; it is not returned to the pool
    assert_eq!(9, pool.size());
}

值可以被手动放入/返回到池中。

extern crate lifeguard;
use lifeguard::*;

fn main() {
    let pool : Pool<String> = pool().with(StartingSize(10)).build();
    {
        let string : String = pool.detached(); // An unwrapped String, detached from the Pool
        assert_eq!(9, pool.size());
        let rstring : Recycled<String> = pool.attach(string); // The String is attached to the pool again
        assert_eq!(9, pool.size()); // but it is still checked out from the pool
    } // rstring goes out of scope and is added back to the pool
    assert_eq!(10, pool.size());
}

Pool 的构建器 API 可以用来自定义池的行为。

extern crate lifeguard;
use lifeguard::*;

fn main() {
 let pool : Pool<String> = pool()
   // The pool will allocate 128 values for immediate use. More will be allocated on demand.
   .with(StartingSize(128))
   // The pool will only grow up to 4096 values. Further values will be dropped.
   .with(MaxSize(4096))
   // The pool will use this closure (or other object implementing Supply<T>) to allocate
   .with(Supplier(|| String::with_capacity(1024)))
   .build();
  // ...
}

非常不科学的基准测试

基准测试源代码可以在 这里 找到。测试在一台早期的 2015 年 MacBook Pro 上运行。

每个基准测试都有三种风味

1. tests::*_standard：使用系统分配器创建新值。
2. tests::*_pooled_rc：使用 Pool 创建新值，这些值持有 Rc 对 Pool 的引用。这些值可以自由传递到其他作用域。
3. tests::*_pooled：使用 Pool 创建新值，这些值持有对 Pool 的本地作用域引用。这些值创建成本最低，但绑定到 Pool 的生命周期。

未初始化的分配

比较创建一个新的 String（使用 String::with_capacity，因为 String::new 不立即分配）与从池中检索 String 的成本。

tests::allocation_standard                          ... bench:   5,322,513 ns/iter (+/- 985,898)
tests::allocation_pooled_rc                         ... bench:     784,885 ns/iter (+/- 95,245)
tests::allocation_pooled                            ... bench:     565,864 ns/iter (+/- 66,036)

tests::initialized_allocation_standard              ... bench:   5,329,948 ns/iter (+/- 547,725)
tests::initialized_allocation_pooled_rc             ... bench:   1,151,493 ns/iter (+/- 119,293)
tests::initialized_allocation_pooled                ... bench:     927,214 ns/iter (+/- 147,935)

tests::vec_vec_str_standard                         ... bench:   1,353,906 ns/iter (+/- 142,094)
tests::vec_vec_str_pooled_rc                        ... bench:     298,087 ns/iter (+/- 168,703)
tests::vec_vec_str_pooled                           ... bench:     251,082 ns/iter (+/- 24,408)