316 lines
8.0 KiB
Groff
316 lines
8.0 KiB
Groff
.\" $NetBSD: vmem.9,v 1.15 2013/01/29 22:02:17 wiz Exp $
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.\"
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.\" Copyright (c)2006 YAMAMOTO Takashi,
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.\" ------------------------------------------------------------
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.Dd July 12, 2013
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.Dt VMEM 9
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.Os
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.\" ------------------------------------------------------------
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.Sh NAME
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.Nm vmem
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.Nd general purpose resource allocator
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.\" ------------------------------------------------------------
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.Sh SYNOPSIS
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.In sys/vmem.h
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.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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.Ft vmem_t *
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.Fn vmem_create \
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"const char *name" "vmem_addr_t base" "vmem_size_t size" "vmem_size_t quantum" \
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"vmem_size_t qcache_max" "int flags"
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.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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.Ft int
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.Fn vmem_add \
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"vmem_t *vm" "vmem_addr_t addr" "vmem_size_t size" "int flags"
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.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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.Ft int
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.Fn vmem_xalloc \
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"vmem_t *vm" "const vmem_size_t size" "vmem_size_t align" \
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"const vmem_size_t phase" "const vmem_size_t nocross" \
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"const vmem_addr_t minaddr" "const vmem_addr_t maxaddr" "int flags" \
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"vmem_addr_t *addrp"
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.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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.Ft void
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.Fn vmem_xfree "vmem_t *vm" "vmem_addr_t addr" "vmem_size_t size"
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.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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.Ft int
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.Fn vmem_alloc "vmem_t *vm" "vmem_size_t size" "int flags" "vmem_addr_t *addrp"
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.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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.Ft void
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.Fn vmem_free "vmem_t *vm" "vmem_addr_t addr" "vmem_size_t size"
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.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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.Ft void
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.Fn vmem_destroy "vmem_t *vm"
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.\" ------------------------------------------------------------
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.Sh DESCRIPTION
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The
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.Nm
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is a general purpose resource allocator.
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Despite its name, it can be used for arbitrary resources
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other than virtual memory.
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.Pp
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.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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.Fn vmem_create
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creates a new vmem arena.
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.Bl -tag -width qcache_max
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.It Fa name
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The string to describe the vmem.
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.It Fa base
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The start address of the initial span.
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Pass
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.Dv 0
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if no initial span is required.
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.It Fa size
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The size of the initial span.
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Pass
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.Dv 0
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if no initial span is required.
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.It Fa quantum
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The smallest unit of allocation.
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.It Fa qcache_max
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The largest size of allocations which can be served by quantum cache.
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It is merely a hint and can be ignored.
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.It Fa flags
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Combination of
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.Xr malloc 9
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wait flag and
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.Nm
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allocation strategy flag:
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.Bl -tag -width M_FIRSTFIT
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.It Dv M_FIRSTFIT
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Prefer allocation performance.
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.It Dv M_BESTFIT
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Prefer space efficiency.
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.El
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.El
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.Pp
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.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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.Fn vmem_add
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adds a span of size
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.Fa size
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starting at
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.Fa addr
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to the arena.
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Returns
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0
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on success,
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.Dv ENOMEM
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on failure.
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.Fa flags
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is
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.Xr malloc 9
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wait flag.
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.Pp
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.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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.Fn vmem_xalloc
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allocates a resource from the arena.
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.Bl -tag -width nocross
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.It Fa vm
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The arena which we allocate from.
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.It Fa size
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Specify the size of the allocation.
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.It Fa align
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If zero, don't care about the alignment of the allocation.
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Otherwise, request a resource segment starting at
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offset
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.Fa phase
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from an
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.Fa align
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aligned boundary.
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.It Fa phase
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See the above description of
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.Fa align .
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If
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.Fa align
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is zero,
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.Fa phase
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should be zero.
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Otherwise,
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.Fa phase
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should be smaller than
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.Fa align .
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.It Fa nocross
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Request a resource which doesn't cross
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.Fa nocross
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aligned boundary.
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.It Fa minaddr
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Specify the minimum address which can be allocated, or
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.Dv VMEM_ADDR_MIN
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if the caller does not care.
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.It Fa maxaddr
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Specify the maximum address which can be allocated, or
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.Dv VMEM_ADDR_MAX
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if the caller does not care.
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.It Fa flags
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A bitwise OR of an allocation strategy and a
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.Xr malloc 9
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wait flag.
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The allocation strategy is one of
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.Dv M_FIRSTFIT
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and
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.Dv M_BESTFIT .
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.It Fa addrp
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On success, if
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.Fa addrp
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is not
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.Dv NULL ,
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.Fn vmem_xalloc
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overwrites it with the start address of the allocated span.
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.El
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.Pp
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.\" ------------------------------------------------------------
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.Fn vmem_xfree
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frees resource allocated by
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.Fn vmem_xalloc
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to the arena.
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.Bl -tag -width addr
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.It Fa vm
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The arena which we free to.
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.It Fa addr
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The resource being freed.
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It must be the one returned by
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.Fn vmem_xalloc .
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Notably, it must not be the one from
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.Fn vmem_alloc .
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Otherwise, the behaviour is undefined.
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.It Fa size
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The size of the resource being freed.
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It must be the same as the
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.Fa size
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argument used for
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.Fn vmem_xalloc .
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.El
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.Pp
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.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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.Fn vmem_alloc
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allocates a resource from the arena.
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.Bl -tag -width flags
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.It Fa vm
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The arena which we allocate from.
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.It Fa size
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Specify the size of the allocation.
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.It Fa flags
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A bitwise OR of an
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.Nm
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allocation strategy flag (see above) and a
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.Xr malloc 9
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sleep flag.
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.It Fa addrp
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On success, if
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.Fa addrp
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is not
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.Dv NULL ,
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.Fn vmem_alloc
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overwrites it with the start address of the allocated span.
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.El
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.Pp
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.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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.Fn vmem_free
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frees resource allocated by
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.Fn vmem_alloc
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to the arena.
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.Bl -tag -width addr
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.It Fa vm
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The arena which we free to.
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.It Fa addr
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The resource being freed.
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It must be the one returned by
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.Fn vmem_alloc .
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Notably, it must not be the one from
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.Fn vmem_xalloc .
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Otherwise, the behaviour is undefined.
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.It Fa size
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The size of the resource being freed.
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It must be the same as the
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.Fa size
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argument used for
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.Fn vmem_alloc .
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.El
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.Pp
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.\" ------------------------------------------------------------
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.Fn vmem_destroy
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destroys a vmem arena.
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.Bl -tag -width vm
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.It Fa vm
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The vmem arena being destroyed.
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The caller should ensure that no one will use it anymore.
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.El
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.\" ------------------------------------------------------------
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.Sh RETURN VALUES
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.Fn vmem_create
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returns a pointer to the newly allocated vmem_t.
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Otherwise, it returns
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.Dv NULL .
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.Pp
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On success,
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.Fn vmem_xalloc
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and
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.Fn vmem_alloc
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return 0.
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Otherwise,
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.Dv ENOMEM
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is returned.
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.\" ------------------------------------------------------------
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.Sh CODE REFERENCES
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The
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.Nm
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subsystem is implemented within the file
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.Pa sys/kern/subr_vmem.c .
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.\" ------------------------------------------------------------
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.Sh SEE ALSO
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.Xr malloc 9
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.Rs
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.%A Jeff Bonwick
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.%A Jonathan Adams
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.%T "Magazines and Vmem: Extending the Slab Allocator to Many CPUs and Arbitrary Resources"
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.%J "2001 USENIX Annual Technical Conference"
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.%D 2001
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.Re
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.\" ------------------------------------------------------------
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.Sh HISTORY
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The
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.Nm
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allocator was originally implemented in
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.Nx .
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It was introduced in
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.Fx 10.0 .
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.Sh AUTHORS
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.An -nosplit
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Original implementation of
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.Nm
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was written by
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.An "YAMAMOTO Takashi" .
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The
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.Fx
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port was made by
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.An "Jeff Roberson" .
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.Sh BUGS
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.Nm
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relies on
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.Xr malloc 9 ,
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so it cannot be used as early during system bootstrap.
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