415 lines
10 KiB
Groff
415 lines
10 KiB
Groff
.\" $NetBSD: vmem.9,v 1.8 2009/12/22 11:56:14 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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.\" ------------------------------------------------------------
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.Dd December 21, 2009
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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 virtual memory 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_addr_t (*allocfn)(vmem_t *, vmem_size_t, vmem_size_t *, vm_flag_t)" \
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"void (*freefn)(vmem_t *, vmem_addr_t, vmem_size_t)" \
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"vmem_t *source" "vmem_size_t qcache_max" "vm_flag_t flags" "int ipl"
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.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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.Ft vmem_addr_t
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.Fn vmem_add \
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"vmem_t *vm" "vmem_addr_t addr" "vmem_size_t size" "vm_flag_t flags"
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.\" - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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.Ft vmem_addr_t
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.Fn vmem_xalloc \
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"vmem_t *vm" "vmem_size_t size" "vmem_size_t align" \
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"vmem_size_t phase" "vmem_size_t nocross" "vmem_addr_t minaddr" \
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"vmem_addr_t maxaddr" "vm_flag_t flags"
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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 vmem_addr_t
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.Fn vmem_alloc "vmem_t *vm" "vmem_size_t size" "vm_flag_t flags"
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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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.Pp
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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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It can be
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.Dv VMEM_ADDR_NULL
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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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.It Fa quantum
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The smallest unit of allocation.
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.It Fa allocfn
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The callback function used to import spans from the backend arena.
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Set both
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.Fa allocfn
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and
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.Fa freefn
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to
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.Dv NULL
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to disable automatic imports.
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.Nm
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calls
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.Fo "(*allocfn)"
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.Fa source
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.Fa size
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.Fa "\*[Am]actualsize"
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.Fa flags
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.Fc
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to import a span of size at least
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.Fa size .
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.Fa allocfn
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should accept the same
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.Fa flags
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as
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.Fn vmem_alloc .
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.Fa allocfn
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must return
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.Dv VMEM_ADDR_NULL
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to indicate failure, or
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else the starting address of the imported span.
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If
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.Fa allocfn
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succeeds, it must write the actual size of the allocation to
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.Fa actualsize .
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The actual size will always be greater than or equal to the requested size.
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.It Fa freefn
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The callback function used to free spans to the backend arena.
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.Fa freefn
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may not be
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.Dv NULL
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unless
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.Fa allocfn
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is
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.Dv NULL .
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.Nm
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calls
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.Fn "(*freefn)" source addr size
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to return to
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.Fa source
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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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that was previously allocated by
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.Fa allocfn .
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.It Fa source
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The backend arena.
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.Fa source
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may be
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.Dv NULL .
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.Nm
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passes
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.Fa source
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as the first argument of
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.Fa allocfn
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and
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.Fa freefn .
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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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Either of:
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.Bl -tag -width VM_NOSLEEP
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.It Dv VM_SLEEP
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Can sleep until enough resources are available.
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.It Dv VM_NOSLEEP
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Don't sleep.
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Immediately return
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.Dv NULL
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if there are not enough resources available.
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.El
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.It Fa ipl
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Interrupt level to be blocked for allocating from vmem.
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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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.Fa addr
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on success.
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.Fa flags
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should be one of:
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.Bl -tag -width VM_NOSLEEP
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.It Dv VM_SLEEP
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Can sleep until enough resources are available.
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.It Dv VM_NOSLEEP
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Don't sleep.
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Immediately return
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.Dv VMEM_ADDR_NULL
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if there are not enough resources available.
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.El
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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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.Pp
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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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If non-zero, specify the minimum address which can be allocated.
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.It Fa maxaddr
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If non-zero, specify the maximum address + 1 which can be allocated.
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.It Fa flags
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A bitwise OR of an allocation strategy and a sleep flag.
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.Pp
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The allocation strategy is one of:
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.Bl -tag -width VM_INSTANTFIT
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.It Dv VM_BESTFIT
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Prefer space efficiency.
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.It Dv VM_INSTANTFIT
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Prefer performance.
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.El
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.Pp
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The sleep flag should be one of:
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.Bl -tag -width VM_NOSLEEP
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.It Dv VM_SLEEP
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Can sleep until enough resources are available.
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.It Dv VM_NOSLEEP
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Don't sleep.
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Immediately return
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.Dv VMEM_ADDR_NULL
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if there are not enough resources available.
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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_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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.Pp
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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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.Pp
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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 allocation strategy and a sleep flag.
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.Pp
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The allocation strategy is one of:
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.Bl -tag -width VM_INSTANTFIT
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.It Dv VM_BESTFIT
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Prefer space efficiency.
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.It Dv VM_INSTANTFIT
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Prefer performance.
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.El
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.Pp
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The sleep flag should be one of:
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.Bl -tag -width VM_NOSLEEP
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.It Dv VM_SLEEP
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Can sleep until enough resources are available.
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.It Dv VM_NOSLEEP
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Don't sleep.
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Immediately return
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.Dv VMEM_ADDR_NULL
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if there are not enough resources available.
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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_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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.Pp
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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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.Pp
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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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return 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 an allocated vmem_addr_t.
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Otherwise,
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.Dv VMEM_ADDR_NULL
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is returned.
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.\" ------------------------------------------------------------
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.Sh CODE REFERENCES
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This section describes places within the
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.Nx
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source tree where actual code implementing the
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.Nm
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subsystem can be found.
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All pathnames are relative to
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.Pa /usr/src .
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.Pp
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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 intro 9 ,
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.Xr kmem 9 ,
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.Xr memoryallocators 9 ,
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.Xr uvm 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 AUTHORS
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This 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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.Sh BUGS
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.Nm
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cannot manage a resource that starts at 0, because it reserves the
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address
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.Dv VMEM_ADDR_NULL
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.Pq 0
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for indicating errors.
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.Pp
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.Nm
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cannot manage a resource that ends at the maximum
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.Vt vmem_addr_t .
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This is an implementation limitation.
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.Pp
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.Nm
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relies on
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.Xr malloc 9 ,
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.Xr pool 9 ,
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and
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.Xr RUN_ONCE 9 ,
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so it cannot be used as early during system bootstrap as
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.Xr extent 9 .
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