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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This number depends on the size of the associated slabs. It eliminates fragmentation caused by allocations and deallocations. A small slab is exactly one page, and has a defined structure that allows bufctls to be avoided.
Retrieved from ” https: Retrieved 28 December 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.
If no such location exists, the system allocates a new slab from contiguous physical pages and assigns it to a cache.
From Wikipedia, the free encyclopedia. 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 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. The next call to allocate memory of the same size will return the now unused memory slot.
The last part of the page contains the ‘slab header’, which is the information needed to retain the slab. This process eliminates the need to search for suitable memory space and greatly alleviates memory fragmentation. Retrieved 18 November 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 Abstract This paper presents a comprehensive design overview of the SunOS 5.
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In this context, a slab is one or more contiguous pages in the memory containing pre-allocated memory chunks. With slab allocation, memory chunks suitable to fit data objects of certain type or size are preallocated.
Advanced Search Include Citations. 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.
Slab allocation – Wikipedia
This article may need to be rewritten entirely to comply with Wikipedia’s quality standards. The discussion page may contain suggestions. Introduction The allocation and freeing of objects are among the most common operations in the kernel. The allocator also has several statistical and debugging features that can detect a wide range of problems throughout the system. A fast kernel memory allocator is therefore essential.
The slab contains a list of bufctls, which are simply controllers for each buffer that can be allocated a buffer is the memory boneick the user of a slab allocator would use. These allocatkr 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. Instead of using bufctls, we use the buffers themselves to retain the free list links.
These same primitives prove equally effective for managing stateless memory e. A slab must contain a list of free buffers or bufctlsas bpnwick as a list of the bufctls that have been allocated in the case of a large slab size.
Initially, the system marks each slab as “empty”. It represents one memory allocation to the cache from the machine, and whose size is customarily a multiple of the page size. Views Read Edit View history. This paper presents a comprehensive design overview of the SunOS 5. The allocator’s object caches respond dynamically to global memory pressure, and aplocator an objectcoloring scheme that improves the system’s overall cache utilization and bus balance.
Slab Allocator | Oracle Jeff Bonwick’s Blog
The notion of object caching was therefore introduced in order to avoid the invocation of functions used to initialize object state. This page was last edited on 23 Decemberat It is analogous to an object poolbut only applies to memory, not other resources. Not to be confused with Slab unit.
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.
However, in many cases the cost of initializing and destroying the object exceeds the cost of allocating and freeing mem 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. 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. 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.