472351e13d
.In header.h instead of .Fd #include \*[Lt]header.h\*[Gt] Much easier to read and write, and supported by groff for ages. Okayed by ross.
147 lines
4.2 KiB
Groff
147 lines
4.2 KiB
Groff
.\" $NetBSD: bufq.9,v 1.6 2003/04/16 13:35:25 wiz Exp $
|
|
.\"
|
|
.\" Copyright (c) 2002 The NetBSD Foundation, Inc.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" This code is derived from software contributed to The NetBSD Foundation
|
|
.\" by Juergen Hannken-Illjes.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the NetBSD
|
|
.\" Foundation, Inc. and its contributors.
|
|
.\" 4. Neither the name of The NetBSD Foundation nor the names of its
|
|
.\" contributors may be used to endorse or promote products derived
|
|
.\" from this software without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
|
|
.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
|
|
.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
|
|
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
|
|
.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
|
.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
|
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
|
.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
|
.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
|
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
.\" POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.Dd July 16, 2002
|
|
.Dt BUFQ 9
|
|
.Os
|
|
.Sh NAME
|
|
.Nm bufq ,
|
|
.Nm bufq_state ,
|
|
.Nm bufq_alloc ,
|
|
.Nm bufq_free ,
|
|
.Nm BUFQ_PUT ,
|
|
.Nm BUFQ_GET ,
|
|
.Nm BUFQ_PEEK
|
|
.Nd device buffer queues
|
|
.Sh SYNOPSIS
|
|
.In buf.h
|
|
.Ft void
|
|
.Fn bufq_alloc "struct bufq_state *bufq" "int flags"
|
|
.Ft void
|
|
.Fn bufq_free "struct bufq_state *bufq"
|
|
.Ft void
|
|
.Fn BUFQ_PUT "struct bufq_state *bufq" "struct buf *bp"
|
|
.Ft "struct buf *"
|
|
.Fn BUFQ_GET "struct bufq_state *bufq"
|
|
.Ft "struct buf *"
|
|
.Fn BUFQ_PEEK "struct bufq_state *bufq"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
subsystem is a set of operations for the management of device buffer queues.
|
|
.Pp
|
|
The primary data type for using the operations is the
|
|
.Em bufq_state
|
|
structure in
|
|
.Pa buf.h :
|
|
.Bd -literal
|
|
struct bufq_state {
|
|
void (*bq_put)(struct bufq_state *, struct buf *);
|
|
struct buf *(*bq_get)(struct bufq_state *, int);
|
|
void *bq_private;
|
|
int bq_flags; /* Flags from bufq_alloc() */
|
|
};
|
|
.Ed
|
|
.Pp
|
|
Valid values for the
|
|
.Em flags
|
|
argument are:
|
|
.Pp
|
|
.Bl -tag -offset indent -width BUFQ_SORT_RAWBLOCK -compact
|
|
.It Dv BUFQ_SORT_RAWBLOCK
|
|
sort by
|
|
.Em b_rawblkno
|
|
.It Dv BUFQ_SORT_CYLINDER
|
|
sort by
|
|
.Em b_cylinder
|
|
and then by
|
|
.Em b_rawblkno
|
|
.It Dv BUFQ_FCFS
|
|
queue strategy is first-come first-serve
|
|
.It Dv BUFQ_DISKSORT
|
|
queue strategy is min seek sort
|
|
.It Dv BUFQ_READ_PRIO
|
|
queue strategy is min seek sort for writes and first-come first-serve
|
|
for reads with read priority
|
|
.El
|
|
.Sh FUNCTIONS
|
|
.Bl -tag -width compact
|
|
.It Fn bufq_alloc "bufq" "flags"
|
|
Initialize a
|
|
.Em bufq_state
|
|
descriptor.
|
|
The argument
|
|
.Fa flags
|
|
controls the strategy and sort order.
|
|
.It Fn bufq_free "bufq"
|
|
Destroy a
|
|
.Em bufq_state
|
|
descriptor.
|
|
.It Fn BUFQ_PUT "bufq" "bp"
|
|
Put the buf
|
|
.Fa bp
|
|
in the queue.
|
|
.It Fn BUFQ_GET "bufq"
|
|
Get the next buf from the queue and remove it from the queue.
|
|
Returns
|
|
.Dv NULL
|
|
if the queue is empty.
|
|
.It Fn BUFQ_PEEK "bufq"
|
|
Get the next buf from the queue without removal.
|
|
The next buf will remain the same until
|
|
.Fn BUFQ_GET
|
|
is called.
|
|
Returns
|
|
.Dv NULL
|
|
if the queue is empty.
|
|
.El
|
|
.Sh CODE REFERENCES
|
|
The actual code implementing the device buffer queues can be found
|
|
in the file
|
|
.Pa sys/kern/subr_disk.c .
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
subsystem appeared in
|
|
.Nx 2.0 .
|
|
.Sh AUTHORS
|
|
The
|
|
.Nm
|
|
subsystem was written by
|
|
.if t .An J\(:urgen Hannken-Illjes
|
|
.if n .An Juergen Hannken-Illjes
|
|
.Aq hannken@NetBSD.org .
|