235 lines
8.0 KiB
C
235 lines
8.0 KiB
C
/* $NetBSD: bufq_readprio.c,v 1.7 2005/12/11 12:24:29 christos Exp $ */
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/* NetBSD: subr_disk.c,v 1.61 2004/09/25 03:30:44 thorpej Exp */
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/*-
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* Copyright (c) 1996, 1997, 1999, 2000 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
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* NASA Ames Research Center.
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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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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* Copyright (c) 1982, 1986, 1988, 1993
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* The Regents of the University of California. All rights reserved.
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* (c) UNIX System Laboratories, Inc.
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* All or some portions of this file are derived from material licensed
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* to the University of California by American Telephone and Telegraph
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* Co. or Unix System Laboratories, Inc. and are reproduced herein with
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* the permission of UNIX System Laboratories, Inc.
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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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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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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* @(#)ufs_disksubr.c 8.5 (Berkeley) 1/21/94
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*/
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#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: bufq_readprio.c,v 1.7 2005/12/11 12:24:29 christos Exp $");
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/buf.h>
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#include <sys/bufq.h>
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#include <sys/bufq_impl.h>
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#include <sys/malloc.h>
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/*
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* Seek sort for disks.
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*
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* There are two queues. The first queue holds read requests; the second
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* holds write requests. The read queue is first-come first-served; the
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* write queue is sorted in ascendening block order.
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* The read queue is processed first. After PRIO_READ_BURST consecutive
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* read requests with non-empty write queue PRIO_WRITE_REQ requests from
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* the write queue will be processed.
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*/
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#define PRIO_READ_BURST 48
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#define PRIO_WRITE_REQ 16
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struct bufq_prio {
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TAILQ_HEAD(, buf) bq_read, bq_write; /* actual list of buffers */
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struct buf *bq_write_next; /* next request in bq_write */
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struct buf *bq_next; /* current request */
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int bq_read_burst; /* # of consecutive reads */
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};
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static void bufq_readprio_init(struct bufq_state *);
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static void bufq_prio_put(struct bufq_state *, struct buf *);
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static struct buf *bufq_prio_get(struct bufq_state *, int);
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BUFQ_DEFINE(readprio, 30, bufq_readprio_init);
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static void
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bufq_prio_put(struct bufq_state *bufq, struct buf *bp)
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{
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struct bufq_prio *prio = bufq->bq_private;
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struct buf *bq;
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int sortby;
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sortby = bufq->bq_flags & BUFQ_SORT_MASK;
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/*
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* If it's a read request append it to the list.
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*/
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if ((bp->b_flags & B_READ) == B_READ) {
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TAILQ_INSERT_TAIL(&prio->bq_read, bp, b_actq);
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return;
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}
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bq = TAILQ_FIRST(&prio->bq_write);
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/*
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* If the write list is empty, simply append it to the list.
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*/
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if (bq == NULL) {
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TAILQ_INSERT_TAIL(&prio->bq_write, bp, b_actq);
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prio->bq_write_next = bp;
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return;
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}
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/*
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* If we lie after the next request, insert after this request.
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*/
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if (buf_inorder(prio->bq_write_next, bp, sortby))
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bq = prio->bq_write_next;
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/*
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* Search for the first request at a larger block number.
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* We go before this request if it exists.
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*/
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while (bq != NULL && buf_inorder(bq, bp, sortby))
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bq = TAILQ_NEXT(bq, b_actq);
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if (bq != NULL)
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TAILQ_INSERT_BEFORE(bq, bp, b_actq);
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else
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TAILQ_INSERT_TAIL(&prio->bq_write, bp, b_actq);
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}
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static struct buf *
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bufq_prio_get(struct bufq_state *bufq, int remove)
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{
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struct bufq_prio *prio = bufq->bq_private;
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struct buf *bp;
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/*
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* If no current request, get next from the lists.
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*/
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if (prio->bq_next == NULL) {
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/*
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* If at least one list is empty, select the other.
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*/
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if (TAILQ_FIRST(&prio->bq_read) == NULL) {
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prio->bq_next = prio->bq_write_next;
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prio->bq_read_burst = 0;
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} else if (prio->bq_write_next == NULL) {
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prio->bq_next = TAILQ_FIRST(&prio->bq_read);
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prio->bq_read_burst = 0;
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} else {
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/*
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* Both list have requests. Select the read list up
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* to PRIO_READ_BURST times, then select the write
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* list PRIO_WRITE_REQ times.
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*/
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if (prio->bq_read_burst++ < PRIO_READ_BURST)
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prio->bq_next = TAILQ_FIRST(&prio->bq_read);
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else if (prio->bq_read_burst <
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PRIO_READ_BURST + PRIO_WRITE_REQ)
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prio->bq_next = prio->bq_write_next;
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else {
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prio->bq_next = TAILQ_FIRST(&prio->bq_read);
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prio->bq_read_burst = 0;
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}
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}
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}
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bp = prio->bq_next;
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if (bp != NULL && remove) {
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if ((bp->b_flags & B_READ) == B_READ)
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TAILQ_REMOVE(&prio->bq_read, bp, b_actq);
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else {
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/*
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* Advance the write pointer before removing
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* bp since it is actually prio->bq_write_next.
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*/
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prio->bq_write_next =
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TAILQ_NEXT(prio->bq_write_next, b_actq);
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TAILQ_REMOVE(&prio->bq_write, bp, b_actq);
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if (prio->bq_write_next == NULL)
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prio->bq_write_next =
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TAILQ_FIRST(&prio->bq_write);
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}
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prio->bq_next = NULL;
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}
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return (bp);
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}
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static void
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bufq_readprio_init(struct bufq_state *bufq)
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{
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struct bufq_prio *prio;
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bufq->bq_get = bufq_prio_get;
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bufq->bq_put = bufq_prio_put;
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bufq->bq_private = malloc(sizeof(struct bufq_prio), M_DEVBUF, M_ZERO);
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prio = (struct bufq_prio *)bufq->bq_private;
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TAILQ_INIT(&prio->bq_read);
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TAILQ_INIT(&prio->bq_write);
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}
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