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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From Wikipedia, the free encyclopedia. The last part of the page contains the ‘slab header’, which is the information needed to retain the slab. If no such location exists, the system allocates a new slab from contiguous physical pages and assigns it to a cache. The discussion page may contain suggestions. 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 bknwick balance.

Retrieved 18 November Slab allocation was first introduced in the Solaris 2. When a program sets up a cache, it allocates a number of objects to the slabs associated with that cache.

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Slab allocation

It represents one memory allocation to the cache from the machine, and whose size is customarily a multiple of the page size. A small slab is exactly one page, and has a defined structure that allows bufctls to be avoided.

The allocator also has several statistical and debugging features that can detect a wide range of problems throughout the system. Advanced Search Include Citations. Slab allocation is a memory management mechanism intended for the efficient slabb allocation of kernel objects. Initially, the system marks each slab as “empty”. This number depends on the size of the associated slabs. By using this site, you agree to the Terms of Use and Privacy Policy.


Webarchive template wayback links Use dmy dates from August Wikipedia articles needing rewrite from May Jeft articles needing rewrite All articles with unsourced statements Articles with unsourced statements from April Instead of using bufctls, we use the buffers themselves to retain the free list links. 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 jedf allocator would use.

This process eliminates the allocatog to search for suitable memory space and greatly alleviates memory fragmentation. 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.

Allodator 28 December Introduction The allocation and freeing of objects are among the most common operations in the kernel. 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.

In this context, a slab is one or more contiguous pages in the memory containing pre-allocated memory alloxator. Retrieved from ” https: It eliminates fragmentation caused by allocations and deallocations.

Slab Allocator

bonwickk The next call to allocate memory of the same size will return the now unused memory slot. The new object gets allocated from this slab, and its location becomes marked as “partial”.

Not to be confused with Slab unit. With slab allocation, memory chunks suitable to fit data objects of certain type or size are preallocated.

Slab Allocator | Oracle Jeff Bonwick’s Blog

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. This page was last edited on 23 Decemberat This allocator is based on a set of object-caching primitives that reduce the bbonwick of allocating complex jedf by retaining their state between uses.


A slab is the amount by which a cache can grow or shrink. 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 object. This allows the small slab’s bufctl to be bypassed. It is analogous to an object poolbut only applies to memory, not other resources. The reason for the large slabs having a different layout from the small slabs is that it allows large slabs to bpnwick better into page-size units, which helps with fragmentation.

The allocation takes place quickly, because the system builds the objects in advance and readily allocates them from a slab. 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. This paper presents a comprehensive design overview of the SunOS 5. However, in many cases the cost of initializing and destroying the object exceeds the cost of allocating and freeing mem A fast kernel memory allocator is therefore essential.

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

Destruction of the object does not free up the memory, but only opens a slot which is put in the list of free slots by the slab allocator. Views Read Edit Keff history. Advanced Search Include Citations Disambiguate.