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.Dd August 3, 2009
.Dt MEMORYALLOCATORS 9
.Os
.Sh NAME
.Nm memoryallocators
.Nd introduction to kernel memory allocators
.Sh DESCRIPTION
The
.Nx
kernel provides several memory allocators, each with different characteristics
and purpose.
This document summarizes the main differences between them.
.Ss The Kmem Allocator
The kmem allocator is modelled after an interface of similar name implemented in
Solaris.
This is main general purpose allocator in the kernel.
.Pp
It is implemented on-top of the
.Xr vmem 9
resource allocator (beyond the scope of this document), meaning it will be using
.Xr pool_cache 9
internally to speed-up common (small) sized allocations.
.Pp
It requires no setup, but cannot be used from interrupt context.
.Pp
See
.Xr kmem 9
for more details.
.Ss The Pool Allocator
The
.Xr pool 9
allocator is a fixed-size memory allocator.
It requires setup (to initialize a memory pool) and is interrupt-safe.
.Pp
.\" On some architectures (foo, bar) the
.\" .Xr pool 9
.\" allocator will use direct-mapped segments rather than normal page
.\" mappings, which can reduce TLB contentions.
.\".Pp
See
.Xr pool 9
for more details.
.Ss The Pool Cache Allocator
The pool cache allocator works on-top of the
.Xr pool 9
allocator, also allowing fixed-size allocation only, requires setup,
and is interrupt-safe.
.Pp
The pool cache allocator is expected to be faster than other allocators,
including the
.Dq normal
pool allocator.
.Pp
In the future this allocator is expected to have a per-CPU cache.
.Pp
See
.Xr pool_cache 9
for more details.
.Ss The UVM Kernel Memory Allocator
This is a low-level memory allocator interface.
It allows variable-sized allocations in multiples of
.Dv PAGE_SIZE ,
and can be used to allocate both wired and pageable kernel memory.
.Pp
See
.Xr uvm 9
for more details.
.Sh SEE ALSO
.Xr intro 9 ,
.Xr kmem 9 ,
.Xr pool 9 ,
.Xr pool_cache 9 ,
.Xr uvm 9 ,
.Xr vmem 9
.Sh AUTHORS
.An Elad Efrat Aq Mt elad@NetBSD.org
.An YAMAMOTO Takashi Aq Mt yamt@NetBSD.org