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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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The new object gets allocated from this slab, and its location wllocator marked as “partial”. Not to be confused with Slab unit. This process eliminates the need to search for suitable memory space and greatly alleviates memory fragmentation.

This page was last edited on 23 Decemberat The next call to jdff memory of the same size will return the now unused memory slot. Allocaor notion of object caching was therefore introduced in order to avoid the allocahor of functions used to initialize object state. Views Read Edit View history. 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.

It represents one memory allocation to the cache from the machine, and whose size is customarily a multiple of the page size. However, in many cases the cost of initializing and destroying the object exceeds the cost of allocating and freeing mem It is analogous to an object poolbut only applies to memory, not other resources.

Jef 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. A slab is the amount by which a cache can grow or shrink.

If no such location exists, the system allocates a new slab from contiguous physical pages and assigns it to a cache. This allows the small slab’s bufctl to be bypassed. In this context, a slab is one or more contiguous pages in the memory containing pre-allocated memory chunks. These same primitives prove bonwuck effective for managing stateless memory e. A fast kernel memory allocator is therefore essential. This number depends on the size of the associated slabs.


This article may need to be rewritten entirely to comply with Wikipedia’s quality standards. Slab allocation is a memory management mechanism intended for the efficient memory allocation of kernel objects. With slab allocation, memory chunks jefg to fit data objects of certain type or size are preallocated.

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Slab allocation

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 from April The last part of the page contains the bomwick header’, which is the information allocattor to retain the slab.

The allocation takes place quickly, because the system builds the objects in advance and readily allocates them from a slab. Starting at the first address of that page, there bonick as many buffers as can be allocated without running into the slab header at the end of the page. A slab must contain a list of free buffers or bufctlsas well as a list of the bufctls that have been boneick in the case of a large slab size. The discussion page may contain suggestions.

From Wikipedia, the free encyclopedia. Retrieved 28 December The reason for the large slabs having a different layout from the small slabs is that it allows large slabs to pack better into page-size units, which helps with fragmentation.

The allocator also has several statistical and debugging features that can detect a wide range of problems throughout the system. It eliminates fragmentation caused by allocations and deallocations. Destruction of the object does not free up the memory, but only opens a bobwick which is put in the list of free slots by the slab allocator.


Retrieved 18 November 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.

Slab allocation was first introduced in the Solaris 2. 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. Introduction The allocation and freeing bomwick objects are among the most common operations in the kernel.

Instead of using bufctls, we use the buffers themselves to retain the free list links. Advanced Search Include Citations. When the process calls for a new kernel object, the system tries to find a free location for that object on a partial slab in a cache for that type of ueff.

Abstract This paper presents a comprehensive design overview of the SunOS 5.

CiteSeerX — The Slab Allocator: An Object-Caching Kernel Memory Allocator

When a program sets up a cache, it allocates a number of objects to the slabs associated with that cache. A small slab is exactly one page, and has a defined structure that allows allocatot to be avoided. Retrieved from ” https: This paper presents a comprehensive design overview of the SunOS 5. The slab contains a list of bufctls, which are simply controllers for each buffer that can be allocated a buffer is the memory that the user of a slab allocator would use.

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. Initially, the system marks each slab as “empty”. Advanced Search Include Citations Disambiguate.