Struct Shared 

pub struct Shared;

A size-classed free list shared by every thread, for a library.

Pooled keeps its lists per thread, which is right for a program that owns its threads. A library loaded into Python or Node does not: the host starts and ends threads, and every thread that ends would leave its lists behind, up to [CLASSES] times the per class cap. These lists belong to the process, so nothing is left behind when a thread ends.

Why a lock per class is still cheaper than the system heap (task-2191). The C library spent about 15% of a single row insert into an indexed table in the Windows heap. A free list here takes one uncontended compare and swap to lock and one store to unlock, and a host calls the library from one thread at a time far more often than from several.

Trait Implementations

impl GlobalAlloc for Shared

unsafe fn alloc(&self, layout: Layout) -> *mut u8

Allocates memory as described by the given layout.

unsafe fn dealloc(&self, pointer: *mut u8, layout: Layout)

Deallocates the block of memory at the given ptr pointer with the given layout.

unsafe fn realloc( &self, pointer: *mut u8, layout: Layout, new_size: usize, ) -> *mut u8

Shrinks or grows a block of memory to the given new_size in bytes. The block is described by the given ptr pointer and layout.

unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8

Behaves like alloc, but also ensures that the contents are set to zero before being returned.