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152 lines
4.4 KiB
Groff
152 lines
4.4 KiB
Groff
.\"
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.\" Copyright (c) 2002 Kenneth D. Merry.
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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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.\" without modification, immediately at the beginning of the file.
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.\" 2. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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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 FOR
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.\" 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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.Dd June 23, 2002
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.Dt JUMBO 9
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.Os
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.Sh NAME
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.Nm jumbo ,
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.Nm jumbo_vm_init ,
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.Nm jumbo_pg_alloc ,
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.Nm jumbo_pg_free ,
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.Nm jumbo_freem ,
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.Nm jumbo_pg_steal ,
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.Nm jumbo_phys_to_kva
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.Nd kernel interface for allocating and freeing page-sized disposable buffers
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.Sh SYNOPSIS
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.In sys/jumbo.h
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.Ft int
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.Fn jumbo_vm_init void
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.Ft vm_page_t
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.Fn jumbo_pg_alloc void
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.Ft void
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.Fn jumbo_pg_free "vm_offset_t addr"
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.Ft void
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.Fn jumbo_freem "caddr_t addr" "void *args"
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.Ft void
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.Fn jumbo_pg_steal "vm_page_t pg"
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.Ft caddr_t
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.Fn jumbo_phys_to_kva "vm_offset_t pa"
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.Sh DESCRIPTION
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The
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.Nm
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buffer facility is designed for allocating disposable page-sized
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buffers.
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Buffers allocated via this facility can either be returned or not.
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This facility is primarily intended for use with network adapters
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that have MTUs of a page or greater size.
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The buffers will normally be disposed of by the
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.Xr zero_copy 9
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receive code.
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.Pp
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.Fn jumbo_vm_init
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initializes the pool of KVA the
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.Nm
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code needs to operate and does some
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other initialization to prepare the subsystem for operation.
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This routine only needs to be called once.
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Calling it multiple times will have no effect.
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It is recommended that this initialization routine be called in a
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device driver attach routine, so that resources are not allocated if the
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.Nm
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subsystem will not end up being used.
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.Fn jumbo_vm_init
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returns 1 upon successful completion, and 0 upon failure.
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.Pp
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.Fn jumbo_pg_alloc
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allocates a physical page and assigns a piece of KVA from the
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.Nm
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KVA pool.
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It returns the allocated page if successful, and
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.Dv NULL
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in the case of failure.
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.Pp
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.Fn jumbo_pg_free
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frees a page allocated by
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.Fn jumbo_pg_alloc .
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It takes the address of the memory in question as an argument.
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This routine will normally be used in cases where the allocated
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.Nm
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page cannot be used for some reason.
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The normal free path is via
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.Fn jumbo_freem .
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.Pp
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.Fn jumbo_freem
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is the routine that should be given as the external free routine when an
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external
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.Vt mbuf
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is allocated using pages from the
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.Nm
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allocator.
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It takes the virtual address of the page in question, and
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ignores the second argument.
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.Pp
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.Fn jumbo_pg_steal
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.Dq steals
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a page and recycles its KVA space.
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.Pp
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.Fn jumbo_phys_to_kva
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translates the physical address of a
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.Nm
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allocated page to the proper kernel virtual address.
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.Sh SEE ALSO
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.Xr ti 4 ,
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.Xr zero_copy 9
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.Sh HISTORY
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The
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.Nm
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allocator is primarily based on a page allocator system originally written
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by
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.An Andrew Gallatin Aq gallatin@FreeBSD.org
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as part of a set of zero copy patches for the
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.Xr ti 4
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driver.
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The allocator was taken out of the
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.Xr ti 4
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driver, cleaned up and ported to the new
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.Xr mutex 9
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interface by
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.An Kenneth Merry Aq ken@FreeBSD.org .
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.Pp
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The
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.Nm
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allocator first appeared in
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.Fx 5.0 ,
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and has existed in patch form since at least 1999.
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.Sh AUTHORS
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.An Andrew Gallatin Aq gallatin@FreeBSD.org
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.An Kenneth Merry Aq ken@FreeBSD.org
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.Sh BUGS
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There is currently a static number of KVA pages allocated by the
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.Nm
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allocator, with no real provision for increasing the number of pages
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allocated should demand exceed supply.
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.Pp
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The
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.Fn jumbo_pg_steal
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function is not currently used anywhere.
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