memoryallocators(9) - NetBSD Manual Pages

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MEMORYALLOCATORS(9)    NetBSD Kernel Developer's Manual    MEMORYALLOCATORS(9)


NAME
memoryallocators -- introduction to kernel memory allocators
DESCRIPTION
The NetBSD kernel provides several memory allocators, each with different characteristics and purpose. This document summarizes the main differ- ences between them. The Malloc Allocator The malloc(9) allocator can be used for variable-sized allocations in the kernel address space. It is interrupt-safe, requires no setup (see below), and is considered to be stable (given the number of years it has been in the kernel). This interface also allows associating a ``type'' with an allocation to indicate what subsystem is using the memory allocated, thus providing statistics as to the memory usage of different kernel subsystems. To define a type, one should use the MALLOC_DEFINE macro, otherwise, one of the built-in types, like M_TEMP can be used. See malloc(9) for more details. The Kmem Allocator The kmem allocator is modelled after an interface of similar name imple- mented in Solaris, and is under active development. It is implemented on-top of the vmem(9) resource allocator (beyond the scope of this document), meaning it will be using pool_cache(9) inter- nally to speed-up common (small) sized allocations. Like malloc(9), it requires no setup, but can't be used yet from inter- rupt context. See kmem_alloc(9), kmem_zalloc(9), and kmem_free(9) for more details. The Pool Allocator The pool(9) allocator is a fixed-size memory allocator. It requires set- up (to initialize a memory pool) and is interrupt-safe. See pool(9) for more details. The Pool Cache Allocator The pool cache allocator works on-top of the pool(9) allocator, also allowing fixed-size allocation only, requires setup, and is interrupt- safe. The pool cache allocator is expected to be faster than other allocators, including the ``normal'' pool allocator. In the future this allocator is expected to have a per-CPU cache. See pool_cache(9) for more details. The UVM Kernel Memory Allocator This is a low-level memory allocator interface. It allows variable-sized allocations in multiples of PAGE_SIZE, and can be used to allocate both wired and pageable kernel memory. See uvm(9) for more details.
SEE ALSO
free(9), intro(9), kmem_alloc(9), kmem_free(9), kmem_zalloc(9), malloc(9), pool(9), pool_cache(9), uvm(9), vmem(9)
AUTHORS
Elad Efrat <elad@NetBSD.org> YAMAMOTO Takashi <yamt@NetBSD.org> NetBSD 5.0 January 7, 2007 NetBSD 5.0
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