The slab allocator: an object-caching kernel memory allocator . Jeff Bonwick, Jonathan Adams, Magazines and Vmem: Extending the Slab. Implementation of the Slab Allocator as described in “The Slab Allocator: An Object-Caching Kernel Memory Allocator” by Jeff Bonwick. – lucastsa/ slab_allocator. This package provides a simple implementation of a Slab memory allocator (Jeff Bonwick: “The Slab Allocator: An Object-Caching Kernel Memory Allocator”).

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A small slab is exactly one page, and has a defined structure that allows bufctls to be avoided. If no such location exists, the system allocates a new slab from contiguous physical pages and assigns it to a cache. Advanced Search Include Citations.

Slab Allocator

This paper presents a comprehensive design overview of the SunOS 5. The notion of object caching was therefore introduced in order to avoid the invocation of functions used to initialize object state.

These small slabs need to be optimized further from the logical layout, by avoiding using bufctls which would be just as large as the data itself and cause memory usage to be much greater.

bonick When a program sets up a cache, it allocates a number of objects to the slabs associated with that cache. The allocation takes place quickly, because the system builds the objects in advance and readily allocates them from a slab.

Boneick The allocation and freeing of objects are among the most common operations in the kernel. In this context, a slab is one or more contiguous pages in the memory containing pre-allocated memory chunks.

The last part of the page contains the ‘slab header’, which is the information needed to retain the slab. The reason for the large slabs having a different layout from allocxtor small slabs is that it allows large slabs to pack better into page-size units, which helps with fragmentation.


The technique is used to retain allocated memory that contains a data object of a certain type for reuse upon subsequent allocations of objects of the same type. A fast kernel memory allocator is therefore essential. Initially, the system marks each slab as “empty”.

Slab Allocator | Oracle Jeff Bonwick’s Blog

This number depends on the size of the associated slabs. With slab allocation, memory chunks suitable to fit data objects of certain type or size are preallocated. Webarchive template wayback links Use dmy dates from August Wikipedia articles needing rewrite from May All articles needing rewrite All articles with unsourced statements Articles with unsourced statements allocatro April alpocator A slab is the amount by which a cache can grow or shrink.

The allocator’s object caches respond dynamically to global memory pressure, and employ an objectcoloring scheme that improves the system’s overall cache utilization and bus balance. Retrieved from ” https: Starting at the first address of that page, there are as many buffers as can be allocated without running into the slab header at the end of the page. Retrieved 28 December It is analogous to an object poolbut only applies to memory, not other resources.

This allocator is based on a set of object-caching primitives that reduce the cost of allocating complex objects by retaining their state between uses. A slab must contain a list of free buffers or bufctlsas well as a list of the bufctls that have been allocated in the case of a large slab size. Slab allocation was first introduced in the Solaris 2. These same primitives prove equally effective for managing stateless memory e. The next call to allocate memory of the same size will return the now unused memory slot.


This process eliminates the need to search for suitable memory allocatot and greatly alleviates jefg fragmentation.

Slab allocation

The allocator also has several statistical and debugging features that can detect a wide range of problems throughout the system. Views Read Edit View history.

It represents one memory allocation to the cache from the machine, and whose size is customarily a multiple of the page size. The primary motivation for slab allocation is that the initialization and destruction of kernel data objects can actually outweigh the cost of allocating memory for them.

The new object gets allocated from this slab, and its location becomes marked as “partial”. By using this site, you agree to the Terms of Use and Privacy Policy. From Wikipedia, the free encyclopedia. When the process calls for a new kernel object, the system tries to find a free location for that object on a partial jevf in a cache for that type of object. Slab allocation is a memory management mechanism intended for the efficient memory allocation of kernel objects. This allows the small slab’s bufctl to be bypassed.